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Study finds virus antibodies in 0.6% of Tokyoites, higher than official infection rate

This supplied electron micrograph shows the new pneumonia-causing coronavirus. (Photo courtesy of the U.S. National Institute of Allergy and Infectious Diseases/Kyodo)

TOKYO -- Antibody tests conducted by researchers to determine the state of novel coronavirus infections in Tokyo suggest that the number of cases in the capital could be many times higher than the officially announced figure.

    Researchers including professor emeritus Tatsuhiko Kodama, a member of the Research Center for Advanced Science and Technology (RCAST) at the University of Tokyo, examined 500 people's blood samples for antibodies. The tests enable researchers to determine whether a person has previously been infected with the novel coronavirus. They found that 0.6% of the samples contained antibodies for the virus on May 15.

    Based on this percentage, it is estimated that the total number of infections in Tokyo, which has a population of 13.98 million people, could be around 83,880 -- about 18 times the figure announced by the Tokyo Metropolitan Government at the time of testing.

    The research was conducted as part of a larger project by a council on the use of novel coronavirus antibody testing, which was convened by institutions including the University of Tokyo, Osaka University and Keio University.

    Official figures do not show exactly how far coronavirus infections have progressed in Japan, as there have been people who showed no symptoms or only light symptoms and have already recovered without being tested.

    The latest study was conducted with assistance from private clinical testing firm LSI Medience Corp. Researchers used residual specimens from 500 people who took blood tests at medical institutions in Tokyo on May 1 and 2. The samples were used with ethics committee approval.

    Takeshi Kawamura, an associate professor in the Isotope Science Center at the University of Tokyo, and other researchers then examined the samples with equipment that can automatically measure the amounts of antibodies, and found three positive results among the 500, for a rate of 0.6%.

    (Japanese original by Ai Yokota, Lifestyle and Medical News Department)

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