4 in 10 COVID-19 Cases Are Asymptomatic Demonstrating Importance of Testing to Mitigate Transmission

Researchers from China showed in a meta-analysis that four in 10 COVID-19 patients are asymptomatic. It included 95 studies from three continents that represent almost 30 million people infected with COVID-19.

The team from Peking University in Beijing revealed that 40% of COVID-19 patients could spread the infection to other people without any symptoms. Meanwhile, there is a 50% chance that pregnant women and travelers are asymptomatic. The study highlights the importance of widely available COVID-19 testing to mitigate transmission.

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4 in 10 COVID-19 Cases Are Asymptomatic: New Study Demonstrates Importance of Testing to Mitigate Transmission

Asymptomatic COVID-19 Cases More Common Than Previously Thought

COVID-19 cases could range from mild and severe cases. For mild cases, this is characterized by cold-like symptoms or no symptoms at all, while severe cases usually require hospitalizations. A previous report from the University of Chicago Medicine showed that asymptomatic patients help spread coronavirus by around 50% because people carry it without realizing they are infected.

The new study from researchers in China, titled "Global Percentage of Asymptomatic SARS-CoV-2 Infections Among the Tested Population and Individuals With Confirmed COVID-19 Diagnosis," published in JAMA Network Open, suggests that asymptomatic COVID-19 cases were maybe even more common than previously believed.

Mail Online reported that researchers defined asymptomatic cases as those who tested in PCR tests but did not have symptoms. Based on the compiled and analyzed data of asymptomatic cases, 40.5% of participants from 95 studies were asymptomatic and certain subgroups have higher numbers of asymptomatic COVID-19 cases.

About 54.1% of pregnant women are asymptomatic, while about 52.9% of travelers on airplanes or cruises are asymptomatic. Also, 39.7% of nursing home residents are infected with COVID-19 but show no symptoms at all.

Furthermore, around 30% of healthcare workers and hospital patients share asymptomatic infections. Researchers also found that North America and Europe share 46.3% and 44.2% asymptomatic cases, respectively, compared to only 27.6% in Asia.

They explained that the lower asymptomatic percentage in Asia might be due to the extensive city-wide SARS-CoV-2 nucleic acid screening program in China.

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COVID-19 Testing and Wearing a Mask Help Mitigate Transmission

Dr. Eric Topol, who also did similar research in 2020, said the findings are significant because of the subgroups transmitting the virus to other people. It shows the importance of pervasive rapid testing to test who is infected with the virus and limit transmission for those asymptomatic cases.

Additionally, it demonstrates the need to test asymptomatic COVID-19 cases before travel. More so, it shows how important it is to put travelers in quarantine to reduce community transmissions, especially in places with low local transmission.

Topol and his colleagues said practicing health protocols, such as social distancing and wearing a face mask, are essential since it is not easy to identify presymptomatic, those who are yet to develop symptoms of COVID-19, and asymptomatic cases, Medical News Today reported. They insist that the high number of asymptomatic cases is a good enough reason to urge people to wear face masks in public.