A large meta-analysis including more than 29 million Covid-19 positive individuals concludes that 40.5% of them do not develop any symptoms of the disease.
- This meta-analysis includes 95 studies and covers a total of more than 29 million individuals who have been tested for Covid-19.
- The results show that 40.5% of people who test positive for Covid-19 do not develop symptoms.
Nearly 4 in 10 people infected with SARS-CoV-2 are asymptomatic. This is the conclusion drawn by researchers from the School of Public Health in Beijing (China) after sifting through 95 unique studies covering 29,776,306 people who were tested. The results were published online Dec. 14 in the journal JAMA Network Open.
40.5% asymptomatic people
To arrive at this result, the researchers examined the percentage of asymptomatic infections for two large cohorts: people who were tested and those whose Covid-19 infection was later confirmed.
The first cohort included the 95 studies, of which 11,516 asymptomatic individuals were examined out of the 29,776,306. This amounts to a percentage of asymptomatic people among the population being screened is 0.25%. This percentage was higher among residents or staff of nursing homes, air or cruise ship travelers and pregnant women, with rates of 4.52%, 2.02% and 2.34%, respectively.
The other analysis including confirmed cases of Covid-19 took place on a smaller cohort. Of the 77 studies studied, the researchers recorded 19,884 cases of Covid-19, including 11,069 asymptomatic forms. This is equivalent to a cumulative percentage of asymptomatic form of 40.5%. Those most likely to be asymptomatic were pregnant women (54.11%), people who had flown or boated (52.91%) and nursing home residents and staff (47.53 %). The number of asymptomatic cases is also higher (60.21%) in those under 20 than in those over 60 (3.69%).
According to the authors, “the high percentage of asymptomatic infections highlights the potential risk of transmission of asymptomatic infections in communities”even if they recall that these figures are statistics and cannot therefore be generalized to the entire population.
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