Superspreader

Last updated

9th floor layout of the Hotel Metropole in Hong Kong, showing where a superspreading event of severe acute respiratory syndrome (SARS) occurred in 2003 Hotel Metropole 9th floor layout SARS 2003.jpg
9th floor layout of the Hotel Metropole in Hong Kong, showing where a superspreading event of severe acute respiratory syndrome (SARS) occurred in 2003

A superspreader is an unusually contagious organism infected with a disease. In the context of a human-borne illness, a superspreader is an individual who is more likely to infect others, compared with a typical infected person. Such superspreaders are of particular concern in epidemiology.

Contents

Some cases of superspreading conform to the 80/20 rule, [1] where approximately 20% of infected individuals are responsible for 80% of transmissions, although superspreading can still be said to occur when superspreaders account for a higher or lower percentage of transmissions. [2] In epidemics with such superspreader events (SSEV), the majority of individuals infect relatively few secondary contacts.[ citation needed ]

SSEVs are shaped by multiple factors including a decline in herd immunity, nosocomial infections, virulence, viral load, misdiagnosis, airflow dynamics, immune suppression, and co-infection with another pathogen. [3]

Defining a superspreader event

Although loose definitions of superspreader events exist, some effort has been made at defining what qualifies as a superspreader event (SSEV). Lloyd-Smith et al. (2005) define a protocol to identify a superspreader event as follows: [2]

  1. estimate the effective reproductive number, R, for the disease and population in question;
  2. construct a Poisson distribution with mean R, representing the expected range of Z due to stochasticity without individual variation;
  3. define an SSEV as any infected person who infects more than Z(n) others, where Z(n) is the nth percentile of the Poisson(R) distribution.

This protocol defines a 99th-percentile SSEV as a case which causes more infections than would occur in 99% of infectious histories in a homogeneous population. [2]

During the SARS-CoV-1 2002–2004 SARS outbreak from China, epidemiologists defined a superspreader as an individual with at least eight transmissions of the disease. [4]

Superspreaders may or may not show any symptoms of the disease. [3] [5]

Writing in Quillette on 23 April 2020 and again a week later in the National Post , Jonathan Kay noticed that in the case of the SARS‑CoV‑2 virus outbreak from China which subsequently turned into the COVID-19 pandemic: [6] [7]

Putting aside hospitals, private residences and old-age homes, almost all of these superspreader events (SSEVs) took place in the context of (1) parties, (2) face-to-face professional networking events and meetings, (3) religious gatherings, (4) sports events, (5) meat-processing facilities, (6) ships at sea, (7) singing groups, and, yes, (8) funerals.

Factors in transmission

How an infection spreads in a community with immunized and non-immunized members. Herd immunity.svg
How an infection spreads in a community with immunized and non-immunized members.

Superspreaders have been identified who excrete a higher than normal number of pathogens during the time they are infectious. This causes their contacts to be exposed to higher viral/bacterial loads than would be seen in the contacts of non-superspreaders with the same duration of exposure. [8]

Basic reproductive number

The basic reproduction number R0 is the average number of secondary infections caused by a typical infective person in a totally susceptible population. [9] The basic reproductive number is found by multiplying the average number of contacts by the average probability that a susceptible individual will become infected, which is called the shedding potential. [2]

R0 = Number of contacts × Shedding potential

Individual reproductive number

The individual reproductive number represents the number of secondary infections caused by a specific individual during the time that individual is infectious. Some individuals have significantly higher than average individual reproductive numbers and are known as superspreaders. Through contact tracing, epidemiologists have identified superspreaders in measles, tuberculosis, rubella, monkeypox, smallpox, Ebola hemorrhagic fever and SARS. [2] [10]

Co-infections with other pathogens

Studies have shown that men with HIV who are co-infected with at least one other sexually transmitted disease, such as gonorrhea, hepatitis C, and herpes simplex 2 virus, have a higher HIV shedding rate than men without co-infection. This shedding rate was calculated in men with similar HIV viral loads. Once treatment for the co-infection has been completed, the HIV shedding rate returns to levels comparable to men without co-infection. [11] [12]

Lack of herd immunity

Herd immunity, or herd effect, refers to the indirect protection that immunized community members provide to non-immunized members in preventing the spread of contagious disease. The greater the number of immunized individuals, the less likely an outbreak can occur because there are fewer susceptible contacts. In epidemiology, herd immunity is known as a dependent happening because it influences transmission over time. As a pathogen that confers immunity to the survivors moves through a susceptible population, the number of susceptible contacts declines. Even if susceptible individuals remain, their contacts are likely to be immunized, preventing any further spread of the infection. [8] [13] The proportion of immune individuals in a population above which a disease may no longer persist is the herd immunity threshold. Its value varies with the virulence of the disease, the efficacy of the vaccine, and the contact parameter for the population. [14] That is not to say that an outbreak can't occur, but it will be limited. [13] [15] [16]

Superspreaders during outbreaks

COVID-19 outbreak 2020

The South Korean spread of confirmed cases of SARS-CoV-2 infection jumped suddenly starting on 19–20 February 2020. On 19 February, the number of confirmed cases increased by 20. On 20 February, 58 [17] or 70 [18] new cases were confirmed, giving a total of 104 confirmed cases, according to the Centers for Disease Control and Prevention Korea (KCDC). According to Reuters , KCDC attributed the sudden jump to 70 cases linked to "Patient 31", who had participated in a gathering in Daegu at the Shincheonji Church of Jesus the Temple of the Tabernacle of the Testimony. [18] On 20 February, the streets of Daegu were empty in reaction to the Shincheonji outbreak. A resident described the reaction, stating "It's like someone dropped a bomb in the middle of the city. It looks like a zombie apocalypse." [18] On 21 February, the first death was reported. [19] According to the mayor of Daegu, the number of suspected cases as of 21 February is 544 among 4,400 examined followers of the church. [20] Later in the outbreak, in May, A 29-year-old man visited several Seoul nightclubs in one night and resulted in accumulated infections of at least 79 other people. [21]

A business conference in Boston (MA) from February 26–28 was a superspreading event.

In New York, a lawyer contracted the illness then spread it to at least twenty other individuals in his community in New Rochelle, creating a cluster of cases that quickly passed 100, [22] accounting for more than half of SARS2 coronavirus cases in the state during early March 2020. [23] For comparison, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, is between 1.4 and 3.9. [24] [25]

In India, Baldev Singh, a preacher returned from Italy and Germany on 06 March resulting in 19 of his relatives having tested positive with 550 people having had direct contact with him. Because of this, India's government fears an outbreak and quarantined on 27 March 2020 in the State of Punjab, 40,000 residents from 20 villages. [26] While initially reported that Baldev Singh had ignored self-quarantine orders, this was disputed by his co-travellers who claimed no orders to quarantine were given by local authorities. [27] [28]

A Tablighi Jamaat religious congregation that took place in Delhi's Nizamuddin Markaz Mosque in early March 2020 was a coronavirus super-spreader event, with more than 4,000 confirmed cases and at least 27 deaths linked to the event reported across the country. Over 9,000 missionaries may have attended the congregation, with the majority being from various states of India, and 960 attendees from 40 foreign countries. On 18 April, 4,291 confirmed cases of COVID-19 linked to this event by the Union Health Ministry represented a third of all the confirmed cases of India. Around 40,000 people, including Tablighi Jamaat attendees and their contacts, were quarantined across the country.

On 11 May 2020, it came to light that a worker at a fish processing plant in Tema, Ghana is believed to have infected over 500 other people with COVID-19. [29]

As of 18 July 2020, more than one thousand suspected superspreading events had been logged, for example a cluster of 187 people who were infected after eating at a Harper's Restaurant and Brew Pub in East Lansing, Michigan. [30]

SARS outbreak 2003

Guangdong Province in southeastern China where the first outbreak of SARS occurred in 2003. Guangdong in China (+all claims hatched).svg
Guangdong Province in southeastern China where the first outbreak of SARS occurred in 2003.

The first cases of SARS occurred in mid-November 2002 in the Guangdong Province of China. This was followed by an outbreak in Hong Kong in February 2003. A Guangdong Province doctor, Liu Jianlun, who had treated SARS cases there, had contracted the virus and was symptomatic. Despite his symptoms, he traveled to Hong Kong to attend a family wedding. He stayed on the ninth floor of the Metropole Hotel in Kowloon, infecting 16 other hotel guests also staying on that floor. The guests then traveled to Canada, Singapore, Taiwan, and Vietnam, spreading SARS to those locations and transmitting what became a global epidemic. [31]

In another case during this same outbreak, a 54-year-old male was admitted to a hospital with coronary heart disease, chronic kidney failure and type II diabetes mellitus. He had been in contact with a patient known to have SARS. Shortly after his admission he developed fever, cough, myalgia and sore throat. The admitting physician suspected SARS. The patient was transferred to another hospital for treatment of his coronary artery disease. While there, his SARS symptoms became more pronounced. Later, it was discovered he had transmitted SARS to 33 other patients in just two days. He was transferred back to the original hospital where he died of SARS.

The SARS outbreak was eventually contained, but not before it caused 8,273 cases and 775 deaths. Within two weeks of the original outbreak in Guangdong Province, SARS had spread to 29 countries. [32]

Measles outbreak 1989

Rates of measles vaccination worldwide in 2010 Measles vaccination coverage world.svg
Rates of measles vaccination worldwide in 2010

Measles is a highly contagious, air-borne virus that reappears even among vaccinated populations. In one Finnish town in 1989, an explosive school-based outbreak resulted in 51 cases, several of whom had been previously vaccinated. One child alone infected 22 others. It was noted during this outbreak that when vaccinated siblings shared a bedroom with an infected sibling, seven out of nine became infected as well. [33]

Typhoid fever

Typhoid fever is a human-specific disease caused by the bacterium Salmonella typhi . It is highly contagious and becoming resistant to antibiotics. [34] S. typhi is susceptible to creating asymptomatic carriers. The most famous carriers are Mary Mallon, known as Typhoid Mary, from New York City, and Mr. N. the Milker, from Folkstone, England. [35] Both were active around the same time. Mallon infected 51 people from 1902 to 1909. Mr. N. infected more than 200 people over 14 years from 1901 to 1915. At the request of health officials, Mr. N. gave up working in food service. Mallon was at first also compliant, choosing other work – but eventually she returned to cooking and caused further outbreaks. She was involuntarily quarantined at Brothers Island in New York, where she stayed until she died in November 1938, aged 69. [36]

It has been found that Salmonella typhi persists in infected mice macrophages that have cycled from an inflammatory state to a non-inflammatory state. The bacteria remain and reproduce without causing further symptoms in the mice, and this helps to explain why carriers are asymptomatic. [37] [38] [39] [40] Identifying superspreaders A method to detect superspreaders in complex networks has been suggested by Kitsak et al. [41]

See also

Related Research Articles

Infection Invasion of an organisms body tissues by disease-causing agents

An infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.

Epidemic A profoundly debilitating, often deadly infectious disease, which proves highly contagious, yet limited to a specific area and period

An epidemic is the rapid spread of disease to a large number of people in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.

Herd immunity Concept in epidemiology

Herd immunity is a form of indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby reducing the likelihood of infection for individuals who lack immunity. Immune individuals are unlikely to contribute to disease transmission, disrupting chains of infection, which stops or slows the spread of disease. The greater the proportion of immune individuals in a community, the smaller the probability that non-immune individuals will come into contact with an infectious individual.

Severe acute respiratory syndrome Respiratory disease caused by the SARS coronavirus (SARS-CoV)

Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by severe acute respiratory syndrome coronavirus, the first-identified strain of the SARS coronavirus species severe acute respiratory syndrome-related coronavirus (SARSr-CoV). The syndrome caused the 2002–2004 SARS outbreak. In late 2017, Chinese scientists traced the virus through the intermediary of Asian palm civets to cave-dwelling horseshoe bats in Yunnan.

Asymptomatic carrier

An asymptomatic carrier is a person or other organism that has become infected with a pathogen, but that displays no signs or symptoms.

Transmission (medicine) Passing of a pathogen from one organism to another

In medicine, public health, and biology, transmission is the passing of a pathogen causing communicable disease from an infected host individual or group to a particular individual or group, regardless of whether the other individual was previously infected.

Basic reproduction number Metric in epidemiology

In epidemiology, the basic reproduction number, or basic reproductive number, denoted , of an infection can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection. The definition describes the state where no other individuals are infected or immunized. Some definitions, such as that of the Australian Department of Health, add absence of "any deliberate intervention in disease transmission". The basic reproduction number is not to be confused with the effective reproduction number , which is the number of cases generated in the current state of a population, which does not have to be the uninfected state. Also, it is important to note that is a dimensionless number and not a rate, which would have units of time−1, or units of time like doubling time.

Mathematical models can project how infectious diseases progress to show the likely outcome of an epidemic and help inform public health interventions. Models use basic assumptions or collected statistics along with mathematics to find parameters for various infectious diseases and use those parameters to calculate the effects of different interventions, like mass vaccination programmes. The modelling can help decide which intervention/s to avoid and which to trial, or can predict future growth patterns, etc.

Contact tracing Finding and identifying people in contact with someone with an infectious disease

In public health, contact tracing is the process of identification of persons who may have come into contact with an infected person ("contacts") and subsequent collection of further information about these contacts. By tracing the contacts of infected individuals, testing them for infection, isolating or treating the infected and tracing their contacts in turn, public health aims to reduce infections in the population. Diseases for which contact tracing is commonly performed include tuberculosis, vaccine-preventable infections like measles, sexually transmitted infections, blood-borne infections, Ebola, some serious bacterial infections, and novel virus infections. The goals of contact tracing are:

Meningococcal disease

Meningococcal disease describes infections caused by the bacterium Neisseria meningitidis. It has a high mortality rate if untreated but is vaccine-preventable. While best known as a cause of meningitis, it can also result in sepsis, which is an even more damaging and dangerous condition. Meningitis and meningococcemia are major causes of illness, death, and disability in both developed and under-developed countries.

An emergent virus is a virus that is either newly appeared, notably increasing in incidence/geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious diseases and raise public health challenges globally, given their potential to cause outbreaks of disease which can lead to epidemics and pandemics. As well as causing disease, emergent viruses can also have severe economic implications. Recent examples include the SARS-related coronaviruses, which have caused the 2002-2004 outbreak of SARS (SARS-CoV-1) and the 2019–20 pandemic of COVID-19 (SARS-CoV-2). Other examples include the human immunodeficiency virus which causes HIV/AIDS; the viruses responsible for Ebola; the H5N1 influenza virus responsible for avian flu; and H1N1/09, which caused the 2009 swine flu pandemic. Viral emergence in humans is often a consequence of zoonosis, which involves a cross-species jump of a viral disease into humans from other animals. As zoonotic viruses exist in animal reservoirs, they are much more difficult to eradicate and can therefore establish persistent infections in human populations.

The index case or patient zero is the first documented patient in a disease epidemic within a population, or the first documented patient included in an epidemiological study. It can also refer to the first case of a condition or syndrome to be described in the medical literature, whether or not the patient is thought to be the first person affected. An index case can achieve the status of a "classic" case study in the literature, as did Phineas Gage, the first known person to exhibit a definitive personality change as a result of a brain injury.

Antibody-dependent enhancement A way in which antibodies can (rarely) make an infection worse instead of better

Antibody-dependent enhancement (ADE), sometimes less precisely called immune enhancement or disease enhancement, is a phenomenon in which binding of a virus to suboptimal antibodies enhances its entry into host cells, followed by its replication. Antiviral antibodies promote viral infection of target immune cells by exploiting the phagocytic FcγR or complement pathway. After interaction with the virus the antibody binds Fc receptors (FcR) expressed on certain immune cells or some of the complement proteins. FcγR binds antibody via its fragment crystallizable region (Fc). This interaction facilitates phagocytosis of the virus-antibody complex by the immune cells. Usually this phagocytosis is accompanied by the virus degradation, but in the case of ADE, it can, on the contrary, cause viral replication, with the subsequent death of immune cells. Thus, the virus “deceives” the process of phagocytosis of immune cells and uses the host's antibodies as a “Trojan horse”. ADE can be induced when the strength of antibody-antigen interaction is below the certain threshold. This phenomenon might lead to both increased virus infectivity and virulence. The viruses that can cause ADE frequently share some common features such as antigenic diversity, abilities to replicate and establish persistence in immune cells. ADE can occur during the development of a primary or secondary viral infection, as well as after vaccination with a subsequent virus challenge. It has been observed mainly with positive-strand RNA viruses. Among them are Flaviviruses such as Dengue virus, Yellow fever virus, Zika virus, Coronaviruses, including alpha- and betacoronaviruses, Orthomyxoviruses such as influenza, Retroviruses such as HIV, and Orthopneumoviruses such as RSV.

Sunetra Gupta Indian novelist and epidemiologist

Sunetra Gupta is an Indian infectious disease epidemiologist and a professor of theoretical epidemiology at the Department of Zoology, University of Oxford. She has performed research on the transmission dynamics of various infectious diseases, including malaria, influenza and COVID-19, and has received the Scientific Medal of the Zoological Society of London and the Rosalind Franklin Award of the Royal Society. Gupta is also a novelist and a recipient of the Sahitya Akademi Award.

Wildlife smuggling and zoonoses Health risks associated with the trade in exotic wildlife

Wildlife trafficking practices have resulted in the emergence of zoonotic diseases. Exotic wildlife trafficking is a multi-billion dollar industry that involves the removal and shipment of mammals, reptiles, amphibians, invertebrates, and fish all over the world. Traded wild animals are used for bushmeat consumption, unconventional exotic pets, animal skin clothing accessories, home trophy decorations, privately owned zoos, and for traditional medicine practices. Dating back centuries, people from Africa, Asia, Latin America, the Middle East, and Europe have used animal bones, horns, or organs for their believed healing effects on the human body. Wild tigers, rhinos, elephants, pangolins, and certain reptile species are acquired through legal and illegal trade operations in order to continue these historic cultural healing practices. Within the last decade nearly 975 different wild animal taxa groups have been legally and illegally exported out of Africa and imported into areas like China, Japan, Indonesia, the United States, Russia, Europe, and South America.

Severe acute respiratory syndrome coronavirus 2 Virus strain that causes coronavirus disease 2019 (COVID-19)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the strain of coronavirus that causes coronavirus disease 2019 (COVID-19), the respiratory illness responsible for the COVID-19 pandemic. Colloquially known as simply the coronavirus, it was previously referred to by its provisional name, 2019 novel coronavirus (2019-nCoV), and has also been called human coronavirus 2019. The World Health Organization declared the outbreak a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020.

Coronavirus disease 2019 Infectious respiratory disease caused by severe acute respiratory syndrome coronavirus 2

Coronavirus disease 2019 (COVID-19) is a contagious respiratory and vascular disease. It is caused by becoming infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is a specific type of coronavirus. Common symptoms include fever, cough, fatigue, shortness of breath or breathing difficulties, and loss of smell and taste. The incubation period, which is the time between becoming infected with the virus and showing symptoms, may range from one to fourteen days. While most people have mild symptoms, some people develop acute respiratory distress syndrome (ARDS) possibly precipitated by cytokine storm, multi-organ failure, septic shock, and blood clots. Longer-term damage to organs has been observed, and there is concern about a significant number of patients who have recovered from the acute phase of the disease but continue to experience a range of effects—including severe fatigue, memory loss and other cognitive issues, low grade fever, muscle weakness, breathlessness, and other symptoms—for months afterwards.

Allison McGeer is a Canadian infectious disease specialist in the Sinai Health System, a Professor at the Dalla Lana School of Public Health and a Senior Clinician Scientist at the Lunenfeld-Tanenbaum Research Institute. McGeer has led investigations into the severe acute respiratory syndrome outbreak in Toronto and worked alongside Donald Low. During the COVID-19 pandemic, McGeer has studied how SARS-CoV-2 survives in the air.

Natalie E. Dean is an American biostatistician specializing in infectious disease epidemiology. Dean is currently an assistant professor of Biostatistics at the University of Florida. Her research involves epidemiological modeling of outbreaks, including Ebola, Zika and coronavirus disease.

COVID-19 spreads from person to person, mainly through the respiratory route, after an infected person coughs, sneezes, sings, talks or breathes. A new infection occurs when droplets or virus containing particles get into the mouth, nose, lungs or eyes of other people who are in close contact with the infected person. Both droplets and aerosols cause infection when people are physically near, and the closer people interact, the more likely they are to be infected. Aerosols, however, remain suspended in the air for longer periods of time, causing airborne transmission particularly in crowded and inadequately ventilated indoor spaces, such as restaurants, choirs, gyms, nightclubs, offices and religious venues. Aerosols are also generated in healthcare settings.

References

  1. ↑ Galvani, Alison P.; May, Robert M. (2005). "Epidemiology: Dimensions of superspreading". Nature. 438 (7066): 293–95. Bibcode:2005Natur.438..293G. doi:10.1038/438293a. PMC   7095140 . PMID   16292292.
  2. 1 2 3 4 5 Lloyd-Smith, JO; Schreiber, SJ; Kopp, PE; Getz, WM (2005). "Superspreading and the effect of individual variation on disease emergence". Nature. 438 (7066): 355–59. Bibcode:2005Natur.438..355L. doi:10.1038/nature04153. PMC   7094981 . PMID   16292310.
  3. 1 2 Stein, Richard A. (2011). "Superspreaders in Infectious Disease". International Journal of Infectious Diseases. 15 (8): 510–13. doi: 10.1016/j.ijid.2010.06.020 . PMC   7110524 . PMID   21737332. The minority of individuals who infect disproportionately more susceptible contacts, as compared to most individuals who infect few or no others, became known as super-spreaders, and their existence is deeply rooted in history: between 1900 and 1907, Typhoid Mary infected 51 individuals, three of whom died, even though she only had an asymptomatic infection.
  4. ↑ Shen, Zhuang; Ning, Fang; Zhou, Weigong; He, Xiong; Lin, Changying; Chin, Daniel P.; Zhu, Zonghan; Schuchat, Anne (2004). "Superspreading SARS Events, Beijing, 2003". Emerging Infectious Diseases. 10 (2): 256–260. doi:10.3201/eid1002.030732. PMC   3322930 . PMID   15030693.
  5. ↑ Cory, David C. Wiley, Amy C. (2013). Encyclopedia of School Health. Los Angeles, CA: Sage. ISBN   978-1412996006. Historically, one of the most famous examples of super-spreading was that of Mary Mallon, better known as Typhoid Mary, who infected many contacts, several of whom died, through food she prepared and consequently contaminated, even thought she did not show symptoms.
  6. ↑ Kay, Jonathan (30 April 2020). "It's not the size of the event, but the behaviour that matters". National Post, a division of Postmedia Network Inc.
  7. ↑ Kay, Jonathan (23 April 2020). "COVID-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons". Quillette Pty Ltd.
  8. 1 2 Kenneth J. Rothman, Sander Greenland, and Timothy L. Lash. Modern Epidemiology, 3rd Edition. 2008. p. 561. Lippincott, Williams & Wilkins. Philadelphia.
  9. ↑ Galvani, Alison P.; May, Robert M. (17 November 2005). "Epidemiology: Dimensions of super-spreading". Nature. 438 (7066): 239–95. Bibcode:2005Natur.438..293G. doi:10.1038/438293a. PMC   7095140 . PMID   16292292.
  10. ↑ De Serres, G; Markowski, F; Toth, E; Landry, M; Auger, D; et al. (2013). "Largest measles epidemic in North America in a decade–Quebec, Canada, 2011: contribution of susceptibility, serendipity, and superspreading events". J Infect Dis. 207 (6): 990–98. doi: 10.1093/infdis/jis923 . PMID   23264672.
  11. ↑ Cohen, M.S. Hoffman; IF; Royce, RA; Kazembe, P; Dyer, JR; Daly, OC; et al. (1997). "Reduction of concentration of HIV-1 in semen after treatment of urethritis: implications for prevention of sexual transmission of HIV-1. AIDSCAP Malawi Research Group". Lancet. 349 (9069): 1868–73. doi:10.1016/s0140-6736(97)02190-9. PMID   9217758.
  12. ↑ Winter, AJ; Taylor, S. Workman J.; White, D.; Ross, JD.; Swan, AV; Pillay, D. (1999). "Asymptomatic urethritis and detection of HIV-1 RNA in seminal plasma". Sex Transm Infect. 75 (261): 261–63. doi:10.1136/sti.75.4.261. PMC   1758225 . PMID   10615314.
  13. 1 2 Fine, P (1993). "Herd immunity: history, theory, practice". Epidemiol Rev. 15 (2): 265–302. doi:10.1093/oxfordjournals.epirev.a036121. PMID   8174658.
  14. ↑ Jamison DT, Breman JG, Measham AR, eds. (2006). "Chapter 4: Cost-Effective Strategies for the Excess Burden of Disease in Developing Countries
    Section: Vaccine-preventable Diseases"    . Priorities in Health: Disease Control Priorities Companion Volume. World Bank Publications. ISBN   0-8213-6260-7.
  15. ↑ Yeung, L. F.; Lurie, P.; Dayan, G.; Eduardo, E.; Britz, P. H.; Redd, S. B.; Papania, M. J.; Seward, J. F. (2005). "A Limited Measles Outbreak in a Highly Vaccinated US Boarding School". Pediatrics. 116 (6): 1287–1291. doi:10.1542/peds.2004-2718. PMID   16322148.
  16. ↑ Fine, P.; Eames, K.; Heymann, D. L. (2011). ""Herd Immunity": A Rough Guide". Clinical Infectious Diseases. 52 (7): 911–916. doi: 10.1093/cid/cir007 . PMID   21427399.
  17. ↑ "코로나19 확진자 104명...31번 환자 연관 신천지교회 대남병원서만 확진자 58명, 1명 사망". 글로벌경제신문 (in Korean). 20 February 2020. Retrieved 16 March 2020.
  18. 1 2 3 Shin, Hyonhee; Cha, Sangmi (2020-02-20). "'Like a zombie apocalypse': Residents on edge as coronavirus cases surge in South Korea". Thomson Reuters. Archived from the original on 2020-02-20. Retrieved 2020-02-20.
  19. ↑ "South Korea reports first coronavirus death as infections linked to church rise". NBC News. Retrieved 2020-02-21.
  20. ↑ "신천지 관련 확진자 76명으로 늘어...대구 교인 의심자만 544명". Chosun.com. 21 February 2020.
  21. ↑ Park Han-na (11 May 2020). "Itaewon cluster caseload rises to 79: Nation adds 35 new cases, 20 in Seoul". The Korea Herald. Archived from the original on 16 May 2020. Retrieved 11 May 2020.
  22. ↑ CNN, Sheena Jones and Christina Maxouris. "New York officials traced more than 50 coronavirus cases back to one attorney". CNN. Retrieved 13 March 2020.
  23. ↑ CNN, Eric Levenson and Kristina Sgueglia. "New York creates 'containment zone' around cluster of coronavirus cases in New Rochelle". CNN. Retrieved 13 March 2020.
  24. ↑ Li Q, Guan X, Wu P, Wang X, Zhou L, Tong Y, et al. (January 2020). "Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia". The New England Journal of Medicine. 382 (13): 1199–1207. doi: 10.1056/NEJMoa2001316 . PMC   7121484 . PMID   31995857.
  25. ↑ Riou J, Althaus CL (January 2020). "Pattern of early human-to-human transmission of Wuhan 2019 novel coronavirus (2019-nCoV), December 2019 to January 2020". Euro Surveillance. 25 (4). doi:10.2807/1560-7917.ES.2020.25.4.2000058. PMC   7001239 . PMID   32019669.
  26. ↑ "India 'super spreader' quarantines 40,000 people". BBC News. 2020-03-27. Retrieved 2020-03-27.
  27. ↑ "Now, police's Moose Wala song blames 1st causality". The Times of India. 2020-03-28. Retrieved 2020-08-17.
  28. ↑ "'Vilification of Baldev based on falsehood'". The Times of India. 2020-03-30. Retrieved 2020-08-17.
  29. ↑ CNN, Bukola Adebayo. "A worker infected 533 others with coronavirus at a factory in Ghana, president says". CNN. Retrieved 11 May 2020. Hundreds of factory workers at a fish processing plant in Ghana have tested positive for the coronavirus, the country's president Nana Akufo-Addo said. All 533 of them contracted the virus from one worker at the factory in the port city of Tema, the president said in his public address to the nation Sunday.
  30. ↑ Cha, Ariana. "'Superspreading' events, triggered by people who may not even know they are infected, propel coronavirus pandemic". Washington Post . Retrieved 18 July 2020.
  31. ↑ "How SARS changed the world in less than six months" (PDF). Archived from the original (PDF) on April 5, 2012. Retrieved February 4, 2016.
  32. ↑ Shen, Zhuang; Fang Ning (February 2004). "Superspreading SARS Events, Beijing 2003". Emerging Infectious Diseases. 10 (2): 256–60. doi:10.3201/eid1002.030732. PMC   3322930 . PMID   15030693.
  33. ↑ Paunio, Mikko; Peltola, Heikki; Davidkin, Irja; Virtanen, Martti; Heinonen, Olli P.; Valle, Martti (1998). "Explosive School-based Measles Outbreak Intense Exposure May Have Resulted in High Risk, Even among Revaccinees". Am J Epidemiol. 148 (11): 1103–10. doi: 10.1093/oxfordjournals.aje.a009588 . PMID   9850133.
  34. ↑ Highfield, Roger (28 November 2006). "Typhoid is with us to stay". The Daily Telegraph . Retrieved 2015-03-03.
  35. ↑ Mortimer, Philip P. (1999). "Mr N the milker, and Dr Koch's concept of the healthy carrier". The Lancet. 353 (9161): 1354–1356. doi:10.1016/S0140-6736(98)11315-6. PMID   10218549.
  36. ↑ Marr, John S. (1999). "Typhoid Mary". The Lancet. 353 (9165): 1714. doi:10.1016/S0140-6736(05)77031-8. PMID   10335825.
  37. ↑ Ng, Tessie M.; Monack, Denise M. (2013). "Revisiting Caspase-11 Function in Host Defense". Cell Host & Microbe. 14 (1): 9–14. doi:10.1016/j.chom.2013.06.009. PMC   3785303 . PMID   23870309.
  38. ↑ Eisele, Nicholas A.; Ruby, Thomas; Jacobson, Amanda; Manzanillo, Paolo S.; Cox, Jeffery S.; Lam, Lilian; Mukundan, Lata; Chawla, Ajay; Monack, Denise M. (2013). "Salmonella Require the Fatty Acid Regulator PPARδ for the Establishment of a Metabolic Environment Essential for Long-Term Persistence". Cell Host & Microbe. 14 (2): 171–182. doi:10.1016/j.chom.2013.07.010. PMC   3785333 . PMID   23954156.
  39. ↑ Geoffrey Mohan (August 14, 2013). "Typhoid Mary case may be cracked, a century later". Los Angeles Times . Retrieved 2015-03-03.
  40. ↑ Donald G. McNeil Jr. (August 26, 2013). "Bacteria study offers clues to Typhoid Mary mystery". The New York Times . Retrieved 2015-03-03.
  41. ↑ M. Kitsak, L.K. Gallos, S. Havlin, F. Liljeros, L. Muchnik, H.E. Stanley, H.A. Makse (2010). "Identification of influential spreaders in complex networks". Nature Physics. 6: 888.CS1 maint: multiple names: authors list (link)
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.