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Against the background of the spread of the corona virus: what is a 'super distributor'? An infectious disease specialist explains

Elizabeth McGraw, professor of entomology and director of the Center for Infectious Disease Dynamics, Pennsylvania State University analyzes the data about the corona epidemic

Protection against the corona virus. Illustration: Image by _freakwave_ from Pixabay
Protection against the corona virus. Illustration: Image by _freakwave_ from Pixabay

Translation: Avi Blizovsky

While the outbreak of the corona virus, which spread from the city of Wuhan in China, is in the news, it is interesting to understand how far its pathogen is spreading around the world. This virus moves from place to place by infecting one person at a time. There are sick people who may not spread the virus much further, but it seems that some of the people infected with the corona virus are what epidemiologists define as "super spreaders".
Elizabeth McGraw, director of the Center for Infectious Disease Dynamics at the University of Pennsylvania, explains what this means and why super-spreaders can be crucial factors in disease transmission.

What is a super distributor?

Researchers currently estimate that a person carrying the corona virus will infect, on average, about 2.6 people. Recent published reports on the Wuhan virus also report a case of a single patient infecting 14 healthcare workers. The thing that classifies it as a super spreader is when it infects an extremely large number of other people.

During an epidemic outbreak, epidemiologists seek to determine whether the superdistributors are one of the causes of the spread. Their existence can accelerate the rate of new infections or significantly expand the geographic distribution of the disease.

In response to superspreaders, officials can recommend different ways to limit their impact and slow the spread of the disease, depending on how the disease is transmitted. Pathogens transmitted through airborne droplets, contaminated surfaces, sexual contact, needles, food or drinking water will require different interventions. For example, the recommendation for face masks will be specific to transmission through the air, while hand washing and sterilization of the surface are required for bacteria that can live for some time on surfaces.

Those with a good immune system actually spread

What are the characteristics of a super distributor?
The question of whether a certain person will be a superspreader or not depends on some combination of the pathogen, the patient's biology, his environment and his behavior at the given time. In a society with so much global connectivity, the ability to move pathogens quickly over great distances, often before people are even aware they are sick, helps create environments ripe for super-spreading.

Some infected people may spread more virus into the environment than others because of the way their immune systems work. People with strong immune systems do not feel sick and therefore may continue with their daily routines, causing them to infect more people. Alternatively, people with weak immune systems who are shedding very high amounts of replicating virus may be very good at transmission even if they minimize their contact with others. People who have more symptoms – for example, cough or sneeze more – can also be better at spreading the virus to new human hosts.

Human behaviors, travel patterns, and degree of contact with others can also contribute to overcrowding. An infected shopkeeper may come into contact with a large number of people each day. An international business traveler may move around the world in a short period of time. A sick worker in the healthcare system may come into contact with a large number of particularly sensitive people considering the presence of other diseases.

When do superdistributors play a key role in an outbreak?

There are several historical examples of super distributors. The most famous is Mary-Typhoid, who in the early 20th century supposedly infected 51 people with typhoid through the food she prepared as a cook. Because Mary was an asymptomatic carrier of the bacteria, she did not feel sick, so she was not motivated to use good hand washing practices.

Over the past two decades, superspreaders have caused several measles outbreaks in the United States. Unvaccinated patients visited crowded places such as schools, hospitals, airplanes and amusement parks where they infected many others.

Superspreaders have also played a key role in outbreaks of other coronaviruses, including SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome). A traveler with SARS who stayed at a hotel in Hong Kong infected several overseas guests who returned home and introduced the virus to four other countries.

In both SARS and MERS, super-spreading occurred mostly in hospitals, with dozens of people infected at a time. In South Korea in 2015, one MERS patient infected over eighty other patients, medical personnel and visitors to an overcrowded emergency department over a three-day period. In this case, proximity to the original patient was the greatest risk factor for getting sick.

Can superspreading occur in any infectious disease?
Yes. Some scientists estimate that in any given outbreak, 20% of the population is usually responsible for causing over 80% of all cases of the disease. Researchers have identified super-spreaders in disease outbreaks from those caused by bacteria, such as tuberculosis, as well as those caused by viruses, including measles, MERS and Ebola.

The good news is that with correct control methods specific to the way pathogens are transmitted - hand washing, masks, quarantine, vaccination, etc. - it is possible to slow down the rate of transmission and stop the spread of epidemics.

For an article in The Conversation

More of the topic in Hayadan:

5 תגובות

  1. Thank you very interesting.
    We will be happy for updates in the month that has passed since it already seems like a real epidemic.

  2. Most of the responses to most of the articles I saw on the science website
    It is of someone who thinks he is more sophisticated than the article and wants to explain something to us

  3. An uninteresting and unimportant article. Need an article that explains:
    A. What is the important difference between SARS, MERS and the new virus.
    B. Why does the Ministry of Health know that the virus will spread in the country?
    third. How to protect yourself from infection.
    A. SARS and MERS were contagious only after the patient had a high fever. On the other hand, the new virus infects before the appearance of fever signs, and apparently people who show no signs of illness at all can be secretly sick and infected.
    B. because of a It is not possible to contain the virus in a limited area with a temperature measurement for every passenger in a transportation system.
    third. Face mask + glasses that are also protected from the side. Sanitizing hands before touching food. Hand disinfection before touching the eye, mouth, nose, genitals, wound. Do not buy unpackaged food. Vegetables and fruits to sin and also to peel. Cooking as long as possible for food that was bought not pre-packaged, preferably in a pressure cooker. Cans and plastic packaging disinfect the outside before opening.

  4. Why does this virus not have a name? Corona = crown = crown. Ten counts of the tree of life, a siege of a city, a siege of a camp, the Atar family
    On road 90 = C and not S...
    K like...three monkeys with their hands...referring to killing behavior
    In San Francisco for the issue of the AIDS epidemic... 1976 as an end to bubbles
    Blackness...and the beginning of AIDS and Ebola.

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