Coronavirus Superspreader: Only a few are responsible for most SARS-CoV-2 infections


Since contact investigations require a large number of personnel, such measures are very expensive in countries with high wages. In India, on the other hand, wage costs are much lower and the health authorities have significantly more staff. For example, the world’s largest contact investigation into the spread of the coronavirus SARS-CoV-2 was launched.

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

Recently, the largest coronavirus study to date was published, in which sources of infection were traced via contacts with infected persons. The aim was to identify where and how most people become infected with SARS-CoV-2. It was again shown that so-called superspreading events – i.e. events where many people are infected at once – play a central role in the spread of the virus.

Largest study of its kind to date
World’s largest contact study on coronavirus spread

An international team from 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 mortality of a total of 575,071 people. The group of persons was determined from 84,965 confirmed COVID-19 cases. This is not only the largest coronavirus contact study, but the largest study of its kind ever conducted for an infectious disease.

The results show that only a small percentage of infected people are responsible for a large proportion of the infections. Only eight percent of the starting persons were responsible for 60 percent of new infections. In 71 percent of the Index patients, the spread ended. They did not infect a single other person.

Contact tracing in rich countries too costly

Especially within families the risk of spreading was particularly high. The general risk of contracting SARS-CoV-2 on contact with an index case was 9 percent within families, but only 2.6 percent outside the household. The health care personnel who treated the infected source persons had a risk of infection of 1.2 percent. The risk of infection was highest (10.7 percent) in close contacts without mouth protection.

“Our study represents the largest empirical evidence of superspreaders that we have seen to date for all infectious diseases,” said Ramanan Laxminarayan, a senior researcher in the research group. Everything points to the fact that superspreaders and superspreading events play a central role in the spread of COVID-19 – both in India and the rest of the world.

The research results also show that children and adolescents in India were responsible for about one third of the infections. “Children are very efficient vectors in this environment, which could not be clearly proven in earlier studies,” explains Laxminarayan. Whether these results can be transferred to Germany, however, will have to be clarified in further studies, as other living conditions such as the multi-generational household predominate in India.

The age of the deceased is also younger in India than in the USA. For example, a large proportion of the fatalities in India were between 50 and 64 years old; in the USA, the age of the deceased is mostly over 60 years. However, it must also be mentioned that the average life expectancy in India is about 10 years less than in the USA. (vb)

In poorer countries like India, SARS-CoV-2 is even more dangerous than in richer countries. India has already reported over 96,000 deaths related to COVID-19. The study also showed that the deceased person died on average after only six days of hospitalization, as clinics often do not have the necessary respiratory equipment. By comparison, the average in the USA is 13 days.

WashingtonNewsday Health and Wellness.


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