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World experts speculate real coronavirus figures multiple times official numbers

A nurse receives a thermometer from a patient with a fever and cough, in Nishiwaki, Hyogo Prefecture, on April 9, 2020. Patients are asked to wait inside their cars before doctors examine them. (Mainichi/Yoshiyuki Hirakawa)

TOKYO -- As the number of novel coronavirus cases keeps rising in Japan and many parts of the world, experts from here and abroad are calling the officially announced number of infections into question, suspecting that there may be even more virus carriers in reality.

As of now, more than 10,000 coronavirus cases have been confirmed in Japan, while the figure stands over 2.5 million worldwide. However, some experts estimate that there were already tens of millions of cases across the globe. Behind the conjecture lies the fact that many of those who contract the novel virus strain show no symptoms and that there is a limit to the amount of testing that can be conducted on suspected cases.

In early April, a research team at the University of Gottingen in Germany released a staggering estimate that as of the end of March 2020 there should have been tens of millions of coronavirus infections around the world.

According to a tally by Johns Hopkins University in the United States, the number of coronavirus cases in the world initially was somewhere around 860,000. Yet when the institution calculated potential numbers of infected individuals by using the fatality rate of coronavirus cases based on a large-scale survey in China as well as the number of deaths in many countries, the estimated number of infections in Italy came to around 3.02 million -- about 28 times the officially confirmed cases of roughly 106,000 at the end of March.

The same study speculated that Spain actually had some 5.72 million coronavirus cases -- 60 times the publicly confirmed 96,000 cases -- and that the U.S. had approximately 11.85 million cases -- 63 times the ascertained 190,000 cases. The Baltimore-based university similarly presumed that Japan actually had some 7,800 cases, four times the 2,000 cases that had been confirmed by that time.

Experts in other countries are also voicing similar suspicions. According to an April 3 report by Reuters, Brendan Murphy, chief medical officer of Australia, stated that the global number of coronavirus cases had likely reached between 5 million and 10 million. Britain's Imperial College London released an estimate that by March 28, some 7 million to 43 million people had been infected with the novel coronavirus in 11 European countries.

Dr. Yasuharu Tokuda, head of the Muribushi Project for Okinawa Residency Programs based in Japan's southernmost prefecture of Okinawa and an expert in clinical epidemiology, commented, "It is likely that the number of infected people is 12 times the officially announced figures (in Japan)." He surmised the figure based on the possibility that some people do not test positive for the virus even though they are infected, as well as the ratio of people with no symptoms or only mild symptoms less than four days after the onset of symptoms who haven't been tested.

"Considering there are emerging countries where the testing systems aren't well organized, it is estimated that the global number of infections is at least 10 times the released figures," Tokuda said.

"Because individuals with mild symptoms, who account for the majority of the cases, are not isolated, they end up spreading the virus. In order to prevent medical systems from falling apart, it is essential to test people at high risk of infection right away and contain virus transmissions by tracking down infection routes and isolating close contacts," he said.

(Japanese original by Yuki Ogawa, Lifestyle and Medical News Department)

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