The detection rate of a novel coronavirus variant perceived to be more transmissible than other variants is rising sharply in Tokyo. The rate exceeded 30% during the seven-day period up to April 4, while the rate was below 10% over a seven-day period in early March, according to the Tokyo Metropolitan Institute of Public Health.
The institute has been testing specimens sent from health care centers across Tokyo collected from people who are infected or likely to have been infected with coronavirus variants.
Since January, the most prevalent virus variants detected carried the E484K mutation, which might reduce the effectiveness of COVID-19 vaccines. Among specimens tested in March, 40% to 60% were E484K mutation viruses.
Since mid-March, however, the virus variant with the N501Y mutation is on a rise. This is the type seen in variants from Britain, South Africa and Brazil, and spreading in the Kansai region. This type is said to be more transmissible, and in the seven-day period up to April 4, the detection rate reached 32.3%.
There is an estimation that daily new infections in Tokyo will reach nearly 1,500 by as early as May if N501Y spreads further in the capital.
The National Institute of Infectious Diseases estimates that among people infected with the novel coronavirus, the proportion of people with virus variants was about 70% in the Kansai region and about 10% in the Tokyo metropolitan area in the beginning of April. It estimates the proportion to reach 70% in Tokyo and surrounding areas by the first half of May.
The head of the institute, Takaji Wakita, said: "The speed of the spread of infections may increase if the number of people infected with the virus variants increases. We need to be vigilant, as what is currently happening in Kansai could happen in Tokyo by around May."
-- Heightened alert for Philippine variant
The National Institute of Infectious Diseases has raised the alert level for the novel coronavirus variant from the Philippines, which was first detected in Japan in March, to the same alert level as the variants from Britain, South Africa and Brazil. As cases of virus variants increase, the institute plans to monitor the Philippine variant along with the other three to improve virus measures in Japan.
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