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98-676: The use of UVGI extends to an array of applications, encompassing food, surface, air, and water disinfection. UVGI devices can inactivate microorganisms including bacteria , viruses , fungi , molds , and other pathogens . Recent studies have substantiated the ability of UV-C light to inactivate SARS-CoV-2 , the strain of coronavirus that causes COVID-19 . UV-C wavelengths demonstrate varied germicidal efficacy and effects on biological tissue. Many germicidal lamps like low-pressure mercury (LP-Hg) lamps , with peak emissions around 254 nm, contain UV wavelengths that can be hazardous to humans . As

196-422: A stem cell transplant , alkylating agents , or corticosteroid therapy , regardless of immunization status; travel to areas where measles commonly occurs or contact with travelers from such an area; and the loss of passive, inherited antibodies before the age of routine immunization. Once the measles virus gets onto the mucosa , it infects the epithelial cells in the trachea or bronchi. Measles virus uses

294-501: A 1914 study that observed metabolic changes in Bacillus anthracis upon exposure to sublethal doses of UV. Frederick Gates, in the late 1920s, offered the first quantitative bactericidal action spectra for Staphylococcus aureus and Bacillus coli, noting peak effectiveness at 265 nm. This matched the absorption spectrum of nucleic acids , hinting at DNA damage as the key factor in bacterial inactivation. This understanding

392-582: A billion people. Vaccination rates have been high enough to make measles relatively uncommon. Adverse reactions to vaccination are rare, with fever and pain at the injection site being the most common. Life-threatening adverse reactions occur in less than one per million vaccinations (<0.0001%). In developing countries where measles is common , the World Health Organization (WHO) recommends two doses of vaccine be given, at six and nine months of age. The vaccine should be given whether

490-453: A correlation between children who take aspirin and the development of Reye syndrome . The use of vitamin A during treatment is recommended to decrease the risk of blindness; however, it does not prevent or cure the disease. A systematic review of trials into its use found no reduction in overall mortality, but two doses (200,000 IU ) of vitamin A was shown to reduce mortality for measles in children younger than two years of age. It

588-441: A decrease in immunization. Symptoms typically begin 10–14 days after exposure. The classic symptoms include a four-day fever (the four Ds) and the three Cs— cough , coryza (head cold, fever, sneezing), and conjunctivitis (red eyes)—along with a maculopapular rash . Fever is common and typically lasts for about one week; the fever seen with measles is often as high as 40 °C (104 °F). Koplik's spots seen inside

686-420: A fan to force air past the UV light. Other systems are installed in forced air systems so that the circulation for the premises moves microorganisms past the lamps. Key to this form of sterilization is placement of the UV lamps and a good filtration system to remove the dead microorganisms. For example, forced air systems by design impede line-of-sight, thus creating areas of the environment that will be shaded from

784-754: A form of modified measles. Modified measles is characterized by a prolonged incubation period , milder, and less characteristic symptoms (sparse and discrete rash of short duration). Complications of measles are relatively common, ranging from mild ones such as diarrhea to serious ones such as pneumonia (either direct viral pneumonia or secondary bacterial pneumonia ), laryngotracheobronchitis (croup) (either direct viral laryngotracheobronchitis or secondary bacterial bronchitis), otitis media , acute brain inflammation , corneal ulceration (leading to corneal scarring ), and in about 1 in 600 unvaccinated infants under 15 months while more rarely in older children and adults, subacute sclerosing panencephalitis , which

882-691: A measles outbreak in the German capital of Berlin resulted in at least 782 cases. In 2017, numbers continued to increase in Europe to 21,315 cases, with 35 deaths. In preliminary figures for 2018, reported cases in the region increased 3-fold to 82,596 in 47 countries, with 72 deaths; Ukraine had the most cases (53,218), with the highest incidence rates being in Ukraine (1209 cases per million), Serbia (579), Georgia (564) and Albania (500). The previous year (2017) saw an estimated measles vaccine coverage of 95% for

980-467: A method for drinking water plants to obtain Cryptosporidium , Giardia or virus inactivation credits. For example, for a 90% reduction of Cryptosporidium , a minimum dose of 2,500 μW·s/cm is required based on EPA's 2006 guidance manual. " Sterilization " is often misquoted as being achievable. While it is theoretically possible in a controlled environment, it is very difficult to prove and

1078-412: A newly made virus. Within days, the measles virus spreads through local tissue and is picked up by dendritic cells and alveolar macrophages , and carried from that local tissue in the lungs to the local lymph nodes. From there it continues to spread, eventually getting into the blood and spreading to more lung tissue, as well as other organs like the intestines and the brain. Functional impairment of

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1176-414: A protein on its surface called hemagglutinin (H protein), to bind to a target receptor on the host cell, which could be CD46 , which is expressed on all nucleated human cells, CD150 , aka signaling lymphocyte activation molecule or SLAM, which is found on immune cells like B or T cells, and antigen-presenting cells, or nectin-4 , a cellular adhesion molecule. Once bound, the fusion, or F protein helps

1274-478: A result, UVGI systems have been primarily limited to applications where people are not directly exposed, including hospital surface disinfection, upper-room UVGI , and water treatment . More recently, the application of wavelengths between 200-235 nm, often referred to as far-UVC , has gained traction for surface and air disinfection. These wavelengths are regarded as much safer due to their significantly reduced penetration into human tissue. Notably, UV-C light

1372-587: A rise in alternative infection control and prevention methods, inconsistent efficacy results, and concerns regarding its safety and maintenance requirements. However, recent events like a rise in multiple drug-resistant bacteria and the COVID-19 pandemic have renewed interest in UVGI for air disinfection. Using UV light for disinfection of drinking water dates back to 1910 in Marseille, France . The prototype plant

1470-473: A second dose of the MMR vaccine is given, it will provide immunity in 99% of children. There is no evidence that the measles vaccine virus can be transmitted to other persons. There is no specific antiviral treatment if measles develops. Instead the medications are generally aimed at treating superinfections, maintaining good hydration with adequate fluids, and pain relief. Some groups, like young children and

1568-462: A somewhat similar proposal in 2014, Australian students designed a system using potato chip (crisp) packet foil to reflect solar UV radiation into a glass tube that disinfects water without power. Sizing of a UV system is affected by three variables: flow rate, lamp power, and UV transmittance in the water. Manufacturers typically developed sophisticated computational fluid dynamics (CFD) models validated with bioassay testing. This involves testing

1666-428: A student of Wells, continued the study of airborne infection and UVGI throughout the 1950s and 60s, conducting significant experiments in a Veterans Hospital TB ward. Riley successfully demonstrated that UVGI could efficiently inactivate airborne pathogens and prevent the spread of tuberculosis. Despite initial successes, the use of UVGI declined in the second half of the 20th century era due to various factors, including

1764-565: A total of 56 energy-efficient UV reactors treating up to 2.2 billion U.S. gallons (8.3 billion liters) a day. Ultraviolet can also be combined with ozone or hydrogen peroxide to produce hydroxyl radicals to break down trace contaminants through an advanced oxidation process . It used to be thought that UV disinfection was more effective for bacteria and viruses, which have more-exposed genetic material, than for larger pathogens that have outer coatings or that form cyst states (e.g., Giardia ) that shield their DNA from UV light. However, it

1862-410: A year, primarily in the developing areas of Africa and Asia. It is one of the leading vaccine-preventable disease causes of death. In 1980, 2.6 million people died from measles, and in 1990, 545,000 died due to the disease; by 2014, global vaccination programs had reduced the number of deaths from measles to 73,000. Despite these trends, rates of disease and deaths increased from 2017 to 2019 due to

1960-615: Is also recommended for children. Among cases reported in the U.S. between 1985 and 1992, death occurred in only 0.2% of cases, but may be up to 10% in people with malnutrition . Most of those who die from the infection are less than five years old. The measles vaccine is effective at preventing the disease, is exceptionally safe, and is often delivered in combination with other vaccines. Vaccination resulted in an 80% decrease in deaths from measles between 2000 and 2017, with about 85% of children worldwide having received their first dose as of 2017. Measles affects about 20 million people

2058-429: Is called photolysis , and requires a higher dose than normal disinfection. The dead microorganisms are not removed from the water. UV disinfection does not remove dissolved organics, inorganic compounds or particles in the water. The world's largest water disinfection plant treats drinking water for New York City . The Catskill-Delaware Water Ultraviolet Disinfection Facility , commissioned on 8 October 2013, incorporates

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2156-433: Is caused by the measles virus , a single-stranded, negative-sense , enveloped RNA virus of the genus Morbillivirus within the family Paramyxoviridae . The virus is highly contagious and is spread by coughing and sneezing via close personal contact or direct contact with secretions. Measles is the most contagious virus known. It remains infective for up to two hours in that airspace or nearby surfaces. Measles

2254-602: Is classically described as a generalized red maculopapular rash that begins several days after the fever starts. It starts on the back of the ears and, after a few hours, spreads to the head and neck before spreading to cover most of the body. The measles rash appears two to four days after the initial symptoms and lasts for up to eight days. The rash is said to "stain", changing color from red to dark brown, before disappearing. Overall, measles usually resolves after about three weeks. People who have been vaccinated against measles but have incomplete protective immunity may experience

2352-444: Is developed from inputs such as water quality, lamp type (power, germicidal efficiency, spectral output, arc length), and the transmittance and dimension of the quartz sleeve. Proprietary CFD software simulates both the flow and radiation profiles. Once the 3D model of the chamber is built, it is populated with a grid or mesh that comprises thousands of small cubes. Germicidal lamp Too Many Requests If you report this error to

2450-416: Is difficult to measure UV dose directly but it can also be estimated from: Bulbs require periodic cleaning and replacement to ensure effectiveness. The lifetime of germicidal UV bulbs varies depending on design. Also, the material that the bulb is made of can absorb some of the germicidal rays. Lamp cooling under airflow can also lower UV output. The UV dose should be calculated using the end of lamp life (EOL

2548-435: Is extremely infectious and its continued circulation in a community depends on the generation of susceptible hosts by birth of children. In communities that generate insufficient new hosts the disease will die out. This concept was first recognized in measles by Bartlett in 1957, who referred to the minimum number supporting measles as the critical community size (CCS). Analysis of outbreaks in island communities suggested that

2646-404: Is given in the figure, with the most effective UV light having a wavelength of 265 nm. This applies to most bacteria and does not change significantly for other microbes. Dosages for a 90% kill rate of most bacteria and viruses range between 2,000 and 8,000 μJ/cm. Larger parasites such as Cryptosporidium require a lower dose for inactivation. As a result, US EPA has accepted UV disinfection as

2744-494: Is important for public health efforts. Measles is not known to occur in other animals. Once a person has become infected, no specific treatment is available, although supportive care may improve outcomes. Such care may include oral rehydration solution (slightly sweet and salty fluids), healthy food, and medications to control the fever. Antibiotics should be prescribed if secondary bacterial infections such as ear infections or pneumonia occur. Vitamin A supplementation

2842-493: Is in theory not as effective on moving air, or when the lamp is perpendicular to the flow, as exposure times are dramatically reduced. However, numerous professional and scientific publications have indicated that the overall effectiveness of UVGI actually increases when used in conjunction with fans and HVAC ventilation, which facilitate whole-room circulation that exposes more air to the UV source. Air purification UVGI systems can be free-standing units with shielded UV lamps that use

2940-399: Is inversely proportional to the square of the distance so it decreases at longer distances. Alternatively, it rapidly increases at distances shorter than 1   m. In the above formula, the UV intensity must always be adjusted for distance unless the UV dose is calculated at exactly 1 m (3.3 ft) from the lamp. The UV dose should be calculated at the furthest distance from the lamp on

3038-476: Is limited, such as with upper-room UVGI air cleaners and water disinfection systems. Precautions are commonly implemented to protect users of these UVGI systems, including: Since the early 2010s there has been growing interest in the far-UVC wavelengths of 200-235 nm for whole-room exposure. These wavelengths are generally considered safer due to their limited penetration depth caused by increased protein absorption. This feature confines far-UVC exposure to

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3136-409: Is measured in light energy per area, i.e. radiant exposure or fluence. The fluence a microbe is exposed to is the product of the light intensity, i.e. irradiance and the time of exposure, according to: Likewise, the irradiance depends on the brightness ( radiant intensity , W/sr) of the UV source, the distance between the UV source and the microbe, the attenuation of filters (e.g. fouled glass) in

3234-451: Is not ideal, as saliva contains many other fluids and proteins which may make it difficult to collect samples and detect measles antibodies. Saliva also contains 800 times fewer antibodies than blood samples do, which makes salivary testing additionally difficult. Positive contact with other people known to have measles adds evidence to the diagnosis. Mothers who are immune to measles pass antibodies to their children while they are still in

3332-796: Is progressive and eventually lethal. In addition, measles can suppress the immune system for weeks to months, and this can contribute to bacterial superinfections such as otitis media and bacterial pneumonia. Two months after recovery there is a 11–73% decrease in the number of antibodies against other bacteria and viruses. The death rate in the 1920s was around 30% for measles pneumonia. People who are at high risk for complications are infants and children aged less than 5 years; adults aged over 20 years; pregnant women; people with compromised immune systems, such as from leukemia , HIV infection or innate immunodeficiency; and those who are malnourished or have vitamin A deficiency . Complications are usually more severe in adults. Between 1987 and 2000,

3430-478: Is rapid and, in terms of primary energy use, approximately 20,000 times more efficient than boiling. UV disinfection is most effective for treating high-clarity, purified reverse osmosis distilled water. Suspended particles are a problem because microorganisms buried within particles are shielded from the UV light and pass through the unit unaffected. However, UV systems can be coupled with a pre-filter to remove those larger organisms that would otherwise pass through

3528-577: Is recognized as the most damaging and carcinogenic . Many standard UVGI systems, such as low-pressure mercury (LP-Hg) lamps, produce broad-band emissions in the UV-C range and also peaks in the UV-B band. This often makes it challenging to attribute damaging effects to a specific wavelength. Nevertheless, longer wavelengths in the UV-C band can cause conditions like photokeratitis and erythema. Hence, many UVGI systems are used in settings where direct human exposure

3626-462: Is recommended that children be immunized against measles at 12 months, generally as part of a three-part MMR vaccine (measles, mumps , and rubella ). The vaccine is generally not given before this age because such infants respond inadequately to the vaccine due to an immature immune system. A second dose of the vaccine is usually given to children between the ages of four and five, to increase rates of immunity. Measles vaccines have been given to over

3724-437: Is resistant to reinfection (until the chlorine off-gasses), UVGI water is not resistant to reinfection. UVGI water must be transported or delivered in such a way as to avoid reinfection. A 2006 project at University of California, Berkeley produced a design for inexpensive water disinfection in resource deprived settings. The project was designed to produce an open source design that could be adapted to meet local conditions. In

3822-479: Is so contagious that if one person has it, 90% of non-immune people who have close contact with them (e.g., household members) will also become infected. Humans are the only natural hosts of the virus, and no other animal reservoirs are known to exist, although mountain gorillas are believed to be susceptible to the disease. Risk factors for measles virus infection include immunodeficiency caused by HIV/AIDS , immunosuppression following receipt of an organ or

3920-430: Is specified in number of hours when the lamp is expected to reach 80% of its initial UV output). Some shatter-proof lamps are coated with a fluorated ethylene polymer to contain glass shards and mercury in case of breakage; this coating reduces UV output by as much as 20%. UV source intensity is sometimes specified as irradiance at a distance of 1 meter, which can be easily converted to radiant intensity . UV intensity

4018-446: Is the most common fatal complication of measles infection and accounts for 56–86% of measles-related deaths. Possible consequences of measles virus infection include laryngotracheobronchitis , sensorineural hearing loss , and—in about 1 in 10,000 to 1 in 300,000 cases — panencephalitis , which is usually fatal. Acute measles encephalitis is another serious risk of measles virus infection. It typically occurs two days to one week after

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4116-442: Is unclear if zinc supplementation in children with measles affects outcomes as it has not been sufficiently studied. There are no adequate studies on whether Chinese medicinal herbs are effective. Most people survive measles, though in some cases, complications may occur. About 1 in 4 individuals will be hospitalized and 1–2 in 1,000 will die. Complications are more likely in children under age 5 and adults over age 20. Pneumonia

4214-547: Is virtually absent in sunlight reaching the Earth's surface due to the absorptive properties of the ozone layer within the atmosphere . The development of UVGI traces back to 1878 when Arthur Downes and Thomas Blunt found that sunlight, particularly its shorter wavelengths, hindered microbial growth. Expanding upon this work, Émile Duclaux , in 1885, identified variations in sunlight sensitivity among different bacterial species. A few years later, in 1890, Robert Koch demonstrated

4312-965: The American Red Cross , the United States CDC , the United Nations Foundation , UNICEF and the WHO. Globally, measles fell 60% from an estimated 873,000 deaths in 1999 to 345,000 in 2005. Estimates for 2008 indicate deaths fell further to 164,000 globally, with 77% of the remaining measles deaths in 2008 occurring within the Southeast Asian region. There were 142,300 measles related deaths globally in 2018, of which most cases were reported from African and eastern Mediterranean regions. These estimates were slightly higher than that of 2017, when 124,000 deaths were reported due to measles infection globally. In 2000,

4410-472: The reverse transcription polymerase chain reaction assay. This method is particularly useful to confirm cases when the IgM antibodies results are inconclusive. For people unable to have their blood drawn , saliva can be collected for salivary measles-specific IgA testing. Salivary tests used to diagnose measles involve collecting a saliva sample and testing for the presence of measles antibodies. This method

4508-469: The CCS for measles is around 250,000. To achieve herd immunity , more than 95% of the community must be vaccinated due to the ease with which measles is transmitted from person to person. In 2011, the WHO estimated that 158,000 deaths were caused by measles. This is down from 630,000 deaths in 1990. As of 2018, measles remains a leading cause of vaccine-preventable deaths in the world. In developed countries

4606-467: The UV light. However, a UV lamp placed at the coils and drain pans of cooling systems will keep microorganisms from forming in these naturally damp places. Ultraviolet disinfection of water is a purely physical, chemical-free process. Even parasites such as Cryptosporidium or Giardia , which are extremely resistant to chemical disinfectants, are efficiently reduced. UV can also be used to remove chlorine and chloramine species from water; this process

4704-557: The UV reactor's disinfection performance with either MS2 or T1 bacteriophages at various flow rates, UV transmittance, and power levels in order to develop a regression model for system sizing. For example, this is a requirement for all public water systems in the United States per the EPA UV manual. The flow profile is produced from the chamber geometry, flow rate, and particular turbulence model selected. The radiation profile

4802-426: The UV system unaffected. The pre-filter also clarifies the water to improve light transmittance and therefore UV dose throughout the entire water column. Another key factor of UV water treatment is the flow rate—if the flow is too high, water will pass through without sufficient UV exposure. If the flow is too low, heat may build up and damage the UV lamp. A disadvantage of UVGI is that while water treated by chlorination

4900-467: The WHO established the Global Measles and Rubella Laboratory Network (GMRLN) to provide laboratory surveillance for measles, rubella , and congenital rubella syndrome . Data from 2016 to 2018 show that the most frequently detected measles virus genotypes are decreasing, suggesting that increasing global population immunity has decreased the number of chains of transmission. Cases reported in

4998-473: The WHO. In November 2024, the WHO and CDC reported that that measles cases increased by 20% last year, primarily due to insufficient vaccine coverage in the world’s poorest and conflict-affected regions. Nearly half of the major outbreaks occurred in Africa, where deaths rose by 37%, the agencies noted. In 2023, approximately 10.3 million cases of the highly contagious disease were reported, up from 8.65 million

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5096-1046: The Wikimedia System Administrators, please include the details below. Request from 172.68.168.236 via cp1112 cp1112, Varnish XID 976441994 Upstream caches: cp1112 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 11:04:30 GMT Measles Measles (probably from Middle Dutch or Middle High German masel(e) ("blemish, blood blister ")) is a highly contagious, vaccine-preventable infectious disease caused by measles virus . Other names include morbilli , rubeola , red measles , and English measles . Both rubella , also known as German measles , and roseola are different diseases caused by unrelated viruses. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever , often greater than 40 °C (104 °F), cough, runny nose , and inflamed eyes . Small white spots known as Koplik's spots may form inside

5194-631: The age of 5 years. In February 2024, the World Health Organization said more than half of the world was at risk of a measles outbreak due to Covid-19 pandemic-related disruptions in that month. All the world regions have reported such outbreaks with the exception of the Americas , though these could still be expected to become hotspots in the future. Death rates during the outbreaks tend to be higher among poorer countries but middle income nations are also heavily impacted, according to

5292-608: The application of UVGI saw a shift from "light curtains" to upper-room UVGI, confining germicidal irradiation above human head level. Despite its dependency on good vertical air movement, this approach yielded favorable outcomes in preventing cross-infections. This was exemplified by Wells' successful usage of upper-room UVGI between 1937 and 1941 to curtail the spread of measles in suburban Philadelphia day schools. His study found that 53.6% of susceptibles in schools without UVGI became infected, while only 13.3% of susceptibles in schools with UVGI were infected. Richard L. Riley, initially

5390-424: The basis for emission limits in product safety standards. The UV-C photobiological spectral band is defined as 100–280 nm, with limits currently applying only from 180 to 280 nm. This reflects concerns about acute damage such as erythema and photokeratitis as well as long-term delayed effects like photocarcinogenesis . However, with the increased safety evidence surrounding UV-C for germicidal applications,

5488-448: The brain may occur. Measles is an airborne disease which spreads easily from one person to the next through the coughs and sneezes of infected people. It may also be spread through direct contact with mouth or nasal secretions . It is extremely contagious: nine out of ten people who are not immune and share living space with an infected person will be infected. Furthermore, measles's reproductive number estimates vary beyond

5586-702: The case fatality rate across the United States was three deaths per 1,000 cases attributable to measles, or 0.3%. In underdeveloped nations with high rates of malnutrition and poor healthcare , fatality rates have been as high as 28%. In immunocompromised persons (e.g., people with AIDS ) the fatality rate is approximately 30%. Even in previously healthy children, measles can cause serious illness requiring hospitalization. One out of every 1,000 measles cases progresses to acute encephalitis , which often results in permanent brain damage. One to three out of every 1,000 children who become infected with measles will die from respiratory and neurological complications. Measles

5684-474: The child is HIV-infected or not. The vaccine is less effective in HIV-infected infants than in the general population, but early treatment with antiretroviral drugs can increase its effectiveness. Measles vaccination programs are often used to deliver other child health interventions as well, such as bed nets to protect against malaria , antiparasite medicine and vitamin A supplements, and so contribute to

5782-542: The context of liquid or solid media, rather than airborne microbes. Shortly after Wells' initial experiments, high-intensity UVGI was employed to disinfect a hospital operating room at Duke University in 1936. The method proved a success, reducing postoperative wound infections from 11.62% without the use of UVGI to 0.24% with the use of UVGI. Soon, this approach was extended to other hospitals and infant wards using UVGI "light curtains", designed to prevent respiratory cross-infections, with noticeable success. Adjustments in

5880-426: The correct wavelength, thus irradiating the environment. The forced flow of air or water through this environment ensures exposure of that air or water. The effectiveness of germicidal UV depends on the UV dose, i.e. how much UV light reaches the microbe (measured as radiant exposure ) and how susceptible the microbe is to the given wavelength(s) of UV light, defined by the germicidal effectiveness curve. The UV dose

5978-425: The existing ACGIH TLVs were revised in 2022. The TLVs for the 222 nm UV-C wavelength (peak emissions from KrCl excimer lamps), following the 2022 revision, are now 161 mJ/cm for eye exposure and 479 mJ/cm for skin exposure over an eight-hour period. For the 254 nm UV wavelength, the updated exposure limit is now set at 6 mJ/cm for eyes and 10 mJ/cm for skin. UV can influence indoor air chemistry, leading to

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6076-559: The expression of necessary proteins, resulting in the death or inactivation of the organism. Recently, it has been shown that these dimers are fluorescent. This process is similar to, but stronger than, the effect of longer wavelengths ( UV-B ) producing sunburn in humans. Microorganisms have less protection against UV and cannot survive prolonged exposure to it. A UVGI system is designed to expose environments such as water tanks , rooms and forced air systems to germicidal UV. Exposure comes from germicidal lamps that emit germicidal UV at

6174-536: The eyes and respiratory system and exacerbate conditions like asthma . The specific pollutants produced depend on the initial air chemistry and the UV source power and wavelength. To control ozone and other indoor pollutants, ventilation and filtration methods are used, diluting airborne pollutants and maintaining indoor air quality. UVC radiation is able to break chemical bonds. This leads to rapid aging of plastics and other material, and insulation and gaskets . Plastics sold as "UV-resistant" are tested only for

6272-551: The eyes and skin can include conditions such as photokeratitis (often termed "snow blindness") and erythema (reddening of the skin), while chronic exposure may heighten the risk of skin cancer . However, the safety and effects of UV vary extensively by wavelength, implying that not all UVGI systems pose the same level of hazards. Humans typically encounter UV light in the form of solar UV, which comprises significant portions of UV-A and UV-B , but excludes UV-C . The UV-B band, able to penetrate deep into living, replicating tissue,

6370-539: The first dose and 90% for the second dose in the region, the latter figure being the highest-ever estimated second-dose coverage. In 2019, the United Kingdom, Albania, the Czech Republic, and Greece lost their measles-free status due to ongoing and prolonged spread of the disease in these countries. In the first 6 months of 2019, 90,000 cases occurred in Europe. As a result of widespread vaccination,

6468-466: The first three months of 2019, were 300% higher than in the first three months of 2018, with outbreaks in every region of the world, even in countries with high overall vaccination coverage where it spread among clusters of unvaccinated people. The numbers of reported cases as of mid-November is over 413,000 globally, with an additional 250,000 cases in DRC (as reported through their national system), similar to

6566-582: The formation of ozone and other potentially harmful pollutants , including particulate pollution . This occurs primarily through photolysis , where UV photons break molecules into smaller radicals that form radicals such as OH. The radicals can react with volatile organic compounds (VOCs) to produce oxidized VOCs (OVOCs) and secondary organic aerosols (SOA). Wavelengths below 242 nm can also generate ozone, which not only contributes to OVOCs and SOA formation but can be harmful in itself. When inhaled in high quantities, these pollutants can irritate

6664-433: The frequently cited range of 12 to 18. The NIH quote this 2017 paper saying: "[a] review in 2017 identified feasible measles R 0 values of 3.7–203.3". People are infectious to others from four days before to four days after the start of the rash. While often regarded as a childhood illness, it can affect people of any age. Most people do not get the disease more than once. Testing for the measles virus in suspected cases

6762-499: The germicidal UV-C range, have evolved over time due to scientific research and changing technology. The American Conference of Governmental Industrial Hygienists (ACGIH) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) have set exposure limits to safeguard against both immediate and long-term effects of UV exposure. These limits, also referred to as Threshold Limit Values (TLVs), form

6860-454: The illuminated volume, decreasing the fluid speed, or recirculating the air or water repeatedly through the illuminated section. This ensures multiple passes so that the UV is effective against the highest number of microorganisms and will irradiate resistant microorganisms more than once to break them down. Microbes are more susceptible to certain wavelengths of UV light, a function called the germicidal effectiveness curve. The curve for E. coli

6958-520: The immune system, which can cause deaths from other diseases. Suppression of the immune system by measles lasts about two years and has been epidemiologically implicated in up to 90% of childhood deaths in third world countries, and historically may have caused rather more deaths in the United States, the UK and Denmark than were directly caused by measles. Although the measles vaccine contains an attenuated strain, it does not deplete immune memory. Measles

7056-620: The increasing trends of infection reported in the earlier months of 2019, compared to 2018. In 2019, the total number of cases worldwide climbed to 869,770. The number of cases reported for 2020 is lower compare to 2019. According to the WHO, the COVID-19 pandemic hindered vaccination campaigns in at least 68 countries, including in countries that were experiencing outbreaks, which caused increased risk of additional cases. In 2022, there were an estimated 136,000 measles deaths globally, mostly among unvaccinated or under vaccinated children under

7154-796: The infected dendritic cells by the measles virus is thought to contribute to measles-induced immunosuppression. Typically, clinical diagnosis begins with the onset of fever and malaise about 10 days after exposure to the measles virus, followed by the emergence of cough , coryza , and conjunctivitis that worsen in severity over 4 days of appearing. Observation of Koplik's spots is also diagnostic. Other possible condition that can result in these symptoms include parvovirus , dengue fever , Kawasaki disease , and scarlet fever . Laboratory confirmation is, however, strongly recommended. Laboratory diagnosis of measles can be done with confirmation of positive measles IgM antibodies or detection of measles virus RNA from throat, nasal or urine specimen by using

7252-502: The lethal effect of sunlight on Mycobacterium tuberculosis , hinting at UVGI's potential for combating diseases like tuberculosis . Subsequent studies further defined the wavelengths most efficient for germicidal inactivation. In 1892, it was noted that the UV segment of sunlight had the most potent bactericidal effect. Research conducted in the early 1890s demonstrated the superior germicidal efficacy of UV-C compared to UV-A and UV-B. The mutagenic effects of UV were first unveiled in

7350-503: The light path, the attenuation of the medium (e.g. microbes in turbid water), the presence of particles or objects that can shield the microbes from UV, and the presence of reflectors that can direct the same UV-light through the medium multiple times. Additionally, if the microbes are not free-flowing, such as in a biofilm , they will block each other from irradiation. The U.S. Environmental Protection Agency (EPA) published UV dosage guidelines for water treatment applications in 1986. It

7448-461: The lower-energy UVB since UVC does not normally reach the surface of the Earth. When UV is used near plastic, rubber, or insulation, these materials may be protected by metal tape or aluminum foil. UVGI can be used to disinfect air with prolonged exposure. In the 1930s and 40s, an experiment in public schools in Philadelphia showed that upper-room ultraviolet fixtures could significantly reduce

7546-421: The measles rash breaks out and begins with very high fever, severe headache, convulsions and altered mentation. A person with measles encephalitis may become comatose , and death or brain injury may occur. For people having had measles, it is rare to ever have a symptomatic reinfection. The measles virus can deplete previously acquired immune memory by killing cells that make antibodies, and thus weakens

7644-606: The measles vaccine and autism ; this incorrect concern has reduced the rate of vaccination and increased the number of cases of measles where immunization rates became too low to maintain herd immunity . Additionally, there have been false claims that measles infection protects against cancer. Administration of the MMR vaccine may prevent measles after exposure to the virus (post-exposure prophylaxis). Post-exposure prophylaxis guidelines are specific to jurisdiction and population. Passive immunization against measles by an intramuscular injection of antibodies could be effective up to

7742-467: The mortality rate is lower, for example in England and Wales from 2007 to 2017 death occurred between two and three cases out of 10,000. In children one to three cases out of every 1,000 die in the United States (0.1–0.2%). In populations with high levels of malnutrition and a lack of adequate healthcare, mortality can be as high as 10%. In cases with complications, the rate may rise to 20–30%. In 2012,

7840-405: The mouth are diagnostic for measles, but are temporary and therefore rarely seen. Koplik spots are small white spots that are commonly seen on the inside of the cheeks opposite the molars. They appear as "grains of salt on a reddish background." Recognizing these spots before a person reaches their maximum infectiousness can help reduce the spread of the disease. The characteristic measles rash

7938-448: The mouth two or three days after the start of symptoms. A red, flat rash which usually starts on the face and then spreads to the rest of the body typically begins three to five days after the start of symptoms. Common complications include diarrhea (in 8% of cases), middle ear infection (7%), and pneumonia (6%). These occur in part due to measles-induced immunosuppression . Less commonly seizures , blindness , or inflammation of

8036-402: The need for technically trained personnel for operation. Water chlorination treats larger organisms and offers residual disinfection, but these systems are expensive because they need special operator training and a steady supply of a potentially hazardous material. Finally, boiling of water is the most reliable treatment method but it demands labour and imposes a high economic cost. UV treatment

8134-414: The neutralizing activity of solar UV irradiation. Various UV-emitting devices can be used for SARS-CoV-2 disinfection, and these devices may help in reducing the spread of infection. SARS-CoV-2 can be inactivated by a wide range of UVC wavelengths, and the wavelength of 222 nm provides the most effective disinfection performance. Disinfection is a function of UV intensity and time. For this reason, it

8232-480: The number of deaths due to measles was 78% lower than in 2000 due to increased rates of immunization among UN member states . Even in countries where vaccination has been introduced, rates may remain high. Measles is a leading cause of vaccine-preventable childhood mortality. Worldwide, the fatality rate has been significantly reduced by a vaccination campaign led by partners in the Measles Initiative :

8330-464: The periphery of the target area. Increases in fluence can be achieved by using reflection, such that the same light passes through the medium several times before being absorbed. Aluminum has the highest reflectivity rate versus other metals and is recommended when using UV. In static applications the exposure time can be as long as needed for an effective UV dose to be reached. In waterflow/airflow disinfection, exposure time can be increased by increasing

8428-704: The previous year. In England and Wales, though deaths from measles were uncommon, they averaged about 500 per year in the 1940s. Deaths diminished with the improvement of medical care in the 1950s but the incidence of the disease did not retreat until vaccination was introduced in the late 1960s. Wider coverage was achieved in the 1980s with the measles, mumps and rubella , MMR vaccine . In 2013–14, there were almost 10,000 cases in 30 European countries. Most cases occurred in unvaccinated individuals and over 90% of cases occurred in Germany, Italy, Netherlands, Romania, and United Kingdom. Between October 2014 and March 2015,

8526-553: The reduction of child deaths from other causes. The Advisory Committee on Immunization Practices (ACIP) recommends that all adult international travelers who do not have positive evidence of previous measles immunity receive two doses of MMR vaccine before traveling, although birth before 1957 is presumptive evidence of immunity. Those born in the United States before 1957 are likely to have been naturally infected with measles virus and generally need not be considered susceptible. There have been false claims of an association between

8624-404: The seventh day after exposure. Compared to no treatment, the risk of measles infection is reduced by 83%, and the risk of death by measles is reduced by 76%. However, the effectiveness of passive immunization in comparison to active measles vaccine is not clear. The MMR vaccine is 95% effective for preventing measles after one dose if the vaccine is given to a child who is 12 months or older; if

8722-416: The severely malnourished, are also given vitamin A , which acts as an immunomodulator that boosts the antibody responses to measles and decreases the risk of serious complications. Treatment is supportive , with ibuprofen or paracetamol (acetaminophen) to reduce fever and pain and, if required, a fast-acting medication to dilate the airways for cough. As for aspirin , some research has suggested

8820-457: The superficial layers of tissue , such as the outer layer of dead skin (the stratum corneum ) and the tear film and surface cells of the cornea . As these tissues do not contain replicating cells, damage to them poses less carcinogenic risk. It has also been demonstrated that far-UVC does not cause erythema or damage to the cornea at levels many times that of solar UV or conventional 254 nm UVGI systems. Exposure limits for UV, particularly

8918-589: The term "disinfection" is generally used by companies offering this service as to avoid legal reprimand. Specialist companies will often advertise a certain log reduction , e.g., 6-log reduction or 99.9999% effective, instead of sterilization. This takes into consideration a phenomenon known as light and dark repair ( photoreactivation and base excision repair , respectively), in which a cell can repair DNA that has been damaged by UV light. Many UVGI systems use UV wavelengths that can be harmful to humans, resulting in both immediate and long-term effects. Acute impacts on

9016-432: The transmission of measles among students. UV and violet light are able to neutralize the infectivity of SARS-CoV-2 . Viral titers usually found in the sputum of COVID-19 patients are completely inactivated by levels of UV-A and UV-B irradiation that are similar to those levels experienced from natural sun exposure . This finding suggests that the reduced incidence of SARS-COV-2 in the summer may be, in part, due to

9114-573: The use of UV to disinfect drinking water supplies, including the US and the UK. UV light is electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays . UV is categorised into several wavelength ranges, with short-wavelength UV (UV-C) considered "germicidal UV". Wavelengths between about 200 nm and 300 nm are strongly absorbed by nucleic acids . The absorbed energy can result in defects including pyrimidine dimers . These dimers can prevent replication or can prevent

9212-410: The virus fuse with the membrane and ultimately get inside the cell. As the virus is a single-stranded negative-sense RNA virus , it includes the enzyme RNA-dependent RNA polymerase (RdRp) which is used to transcribe its genome into a positive-sense mRNA strand. After entering a cell, it is ready to be translated into viral proteins, wrapped in the cell's lipid envelope, and sent out of the cell as

9310-442: The womb, especially if the mother acquired immunity through infection rather than vaccination. Such antibodies will usually give newborn infants some immunity against measles, but these antibodies are gradually lost over the course of the first nine months of life. Infants under one year of age whose maternal anti-measles antibodies have disappeared become susceptible to infection with the measles virus. In developed countries, it

9408-640: Was recently discovered that ultraviolet radiation can be somewhat effective for treating the microorganism Cryptosporidium . The findings resulted in the use of UV radiation as a viable method to treat drinking water. Giardia in turn has been shown to be very susceptible to UV-C when the tests were based on infectivity rather than excystation. It has been found that protists are able to survive high UV-C doses but are sterilized at low doses. UV water treatment devices can be used for well water and surface water disinfection. UV treatment compares favourably with other water disinfection systems in terms of cost, labour and

9506-779: Was shut down after a short time due to poor reliability. In 1955, UV water treatment systems were applied in Austria and Switzerland; by 1985 about 1,500 plants were employed in Europe. In 1998 it was discovered that protozoa such as cryptosporidium and giardia were more vulnerable to UV light than previously thought; this opened the way to wide-scale use of UV water treatment in North America. By 2001, over 6,000 UV water treatment plants were operating in Europe. Over time, UV costs have declined as researchers develop and use new UV methods to disinfect water and wastewater. Several countries have published regulations and guidance for

9604-668: Was solidified by the 1960s through research demonstrating the ability of UV-C to form thymine dimers , leading to microbial inactivation. These early findings collectively laid the groundwork for modern UVGI as a disinfection tool. The utilization of UVGI for air disinfection began in earnest in the mid-1930s. William F. Wells demonstrated in 1935 that airborne infectious organisms, specifically aerosolized B. coli exposed to 254 nm UV, could be rapidly inactivated. This built upon earlier theories of infectious droplet nuclei transmission put forth by Carl Flügge and Wells himself. Prior to this, UV radiation had been studied predominantly in

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