The British variant of the coronavirus that causes COVID-19 is 1.32 times more infectious than the original virus, a Japanese study has found.
The study by the National Institute of Infectious Diseases, which covered 803 cases of the British variant, compares with overseas studies that found the variant’s infectivity is 43% to 90% higher than the original’s.
According to the Japanese institute, the variant’s effective reproduction number, or the average number of infections from a carrier of the variant, came to 1.23 for a period between February and late March, against the original’s 0.94.
Given the possibility of an initial failure to identify the British variant in some coronavirus cases, the variant’s reproduction number may have actually been higher than the Japanese study showed.
The institute warned that in light of the British variant’s strong infectivity, existing measures may not be enough to contain the pandemic.
The institute also found that the share of people under 18 among carriers of the British variant is larger than their share among carriers of the original virus.
Children age at 5 or younger accounted for 4.3% of the surveyed British variant cases, against 2.1% of the surveyed original-virus cases.
The proportion of those aged between 6 and 17 stood at 10.3% among the variant cases, against 5.7% among the original-virus cases.
Meanwhile, sample surveys conducted in Hyogo Prefecture suggested that COVID-19 variants are now responsible for more than 90% of new coronavirus cases in the prefecture, the Hyogo Prefectural Government said Thursday.
According to the prefectural government, coronavirus variants were detected in 70, or 93.3%, of 75 people who tested positive for the coronavirus in the prefecture between March 22 and 28.
In a separate study by the city of Kobe, coronavirus variants were identified in 141, or 76.2%, of 185 new infection cases in the city in the same period, with the British variant found in 129 cases.
As over 40% of the British variant cases were not linked to earlier-known cases where variants were detected, “we have to admit a community spread of variants now,” Kobe Mayor Kizo Hisamoto said.
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