Where most SARS-CoV-2 infections occur – naturopathic and naturopathic specialist portal

The world’s largest contact survey into the spread of the coronavirus

The largest coronavirus study to date was recently published, in which sources of infection were traced through contact with infected people. This should identify where and how most people get infected with SARS-CoV-2. So-called super-spread events – that is, events where many people are infected at once – have again been shown to play a central role in the spread of the virus.

The largest contact tracing ever for an infectious disease to date shows that the majority of SARS-CoV-2 infections are spread by only a few people with the disease. (Image: lassedesignen / stock.adobe.com)

Researchers from various institutions in America and India have conducted the largest contact study to date on the SARS-CoV-2 coronavirus. The contacts of more than half a million people in India who have come in contact with the virus have been traced. Research suggests that only a small proportion of those infected are responsible for most infections. More than 70 percent of the participants did not infect any other person. The results of the research were recently presented in the famous journal “Science”.

Tracing contacts in rich countries is too expensive

Since contact investigations are highly staffed, such measures are very expensive in high-wage countries. In India, on the other hand, labor costs are much lower and the health authorities have many more employees. This helped set up the world’s largest contact investigation into the spread of the SARS-CoV-2 coronavirus.

The largest study of its kind to date

An international team from the Princeton Environmental Institute, Johns Hopkins University and the University of California worked with public health officials in the southeastern Indian states of Tamil Nadu and Andhra Pradesh to track the pathways of infection and the death rate of a total of 575,071 people. The group of people was determined from 84,965 confirmed cases of COVID-19. Not only is this the largest contact study on coronaviruses, but also the largest study of its kind ever for an infectious disease.

Super spreaders are responsible for the majority of infections

According to the results, only a small percentage of infected people are responsible for the majority of infections. Only eight percent of the initial people caused 60 percent of the new infections. The spread ended in 71 percent of index patients. They did not infect any other person.

The risk of spread was particularly high within families. The general risk of becoming infected with SARS-CoV-2 from an index case was 9% within families, but only 2.6% outside the household. Health workers who treated those infected had a 1.2 percent risk of infection. The risk of infection (10.7%) was highest in close contacts without a face shield.

“Our study represents the largest empirical evidence of super-spreaders that we have seen so far for all infectious diseases,” said Ramanan Laxminarayan, principal investigator of the working group. Everything indicates that super-spreaders and mass-market events are playing a central role in the spread of COVID-19 – both in India and the rest of the world.

Spread among children and young people underestimated

Research also shows that children and young people in India are responsible for around a third of infections. “In this environment, children are very effective carriers, which has not yet been clearly demonstrated in previous studies,” explains Laxminarayan. However, the question of whether these results can be transferred to Germany needs to be clarified in further surveys, as in India different living conditions such as multigenerational household prevail.

COVID-19 Deaths in India

In poorer countries like India, SARS-CoV-2 is even more dangerous than in richer countries. India has already reported more than 96,000 deaths linked to COVID-19. The study also showed that the deceased died after an average of six days in hospital, as clinics often lack the necessary ventilators. By comparison, this average is 13 days in the United States.

People with COVID-19 in India die younger

The age of the deceased is also younger in India than in the United States. The majority of deaths in India were between 50 and 64 years old, in the United States the age of the deceased is usually over 60. However, it should also be mentioned that the average life expectancy in India is about 10 years lower than the life expectancy in the United States. (v)

Author and source information

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This text conforms to the requirements of specialized medical literature, medical directives and current studies and has been verified by health professionals.


Graduate Editor (FH) Volker Blasek


Princeton University: Largest COVID-19 Contact Tracing Study to Date Finds Children Key to Spread, Evidence from Super Spreaders (Posted: 09/30/2020), ramanan Laxminarayan, Brian princeton.edu Wahl, Shankar Reddy Dudala, among others: Epidemiology and transmission dynamics of COVID-19 in two Indian states; in: Science, 2020, science.sciencemag.org

Important note:
This article is provided for informational purposes only and should not be used for self-diagnosis or self-treatment. It cannot replace a visit to the doctor.