Several patients who have tested positive in Japan for the new coronavirus from China are in a serious condition with very severe symptoms, including some who have difficulty breathing, informed sources said Tuesday.

Some of the patients are elderly and have serious underlying diseases. One of them had a fever earlier this month and took a test for the flu, but the test was negative, according to the sources. The person later tested positive for the new coronavirus.

While many people infected with the new virus only show symptoms similar to those of a mild cold, elderly patients may see their conditions become serious, experts said. Earlier this month, a Japanese man in his 60s infected with the virus died in the Chinese city of Wuhan, which is at the center of the viral outbreak.

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