80% of COVID-19 is spread from people who do not know that they are sick

March 16 (UPI) – People who don’t know that they have a new coronavirus can inadvertently spread it, an analysis published on Monday in the journal The science offers.

Using data from China – where COVID-19 There was an outbreak – epidemiologists have developed a mathematical model for the spread of infectious diseases. The model estimates almost 80 percent of confirmed cases of the disease, originating from the so-called "undocumented" cases, or those that experienced mild, limited or absent symptoms and were not diagnosed as a result.

Researchers believe that the findings help explain the rapid spread of the virus in the world.

“When someone is experiencing mild symptoms, and most of us can relate to this, we still go on our day and send the kids to school and go to work, and they may have a headache or a little fever and maybe take Ibuprofen and going and going shopping and much more, ”said research co-author Jeffrey Shaman, professor of environmental health at Columbia University, at a press briefing on Monday. "It is constant contact with people that allows the transmission of many respiratory viruses."

As of Monday, 175,000 confirmed cases of COVID-19 have been reported worldwide, affecting 127 countries. This weekend, for the first time, the number of cases reported outside of China overshadowed the total number of cases within the country.

The authors of the new article — all of which are based outside of China — have developed a mathematical model that simulates the “spatiotemporal dynamics” of infections among 375 Chinese cities. They divided COVID-19 infections into two types: confirmed, documented, infected people with symptoms and unregistered infected people, the latter based on estimates.

The researchers calculated individual transmission rates for each of these two types based on population and the movement of people between places.
With this approach, the authors estimated that prior to travel restrictions on January 23, 86% of all infections in China were unregistered. This corresponds to almost 82,000 confirmed cases, which probably make up only a fraction of the total number of cases.

According to Ira Longini Jr., a professor of biostatistics at the University of Florida, the results indicate that in each of the seven cases of COVID-19, symptoms are observed with serious enough symptoms to confirm the diagnosis – because only those who have severe symptoms pass treatment. ,

“If you project this number worldwide, given that we have 150,000 confirmed cases, we are approaching nearly a million infections,” said Longini, who was not part of the research team. "We could argue or dispute what a particular number is – and there may be one in ten in some societies versus one in five and others."

According to Longini, this corresponds to 3,500 confirmed cases of the disease in the United States, which could be 35,000 cases.

The authors estimate that per person the transmission rate of unregistered infections was 55 percent of reported infections. However, because of their greater number, unregistered infections were the source of infection for 79 percent of reported cases.

“With the advent of the new coronavirus, we wanted to identify factors supporting the rapid geographical distribution that we observed in China as it moved between countries,” said the Shaman.

“Since there are many more such undocumented cases, it is unregistered infections that contribute to the spread and growth of the outbreak,” said the Shaman. "Undocumented infections, which are usually milder, spread the virus widely and make a significant contribution to what they call covert transmission of the virus because it is not detected and flies below the radar."

. (TagsToTranslate) Health (s) COVID-19

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