TOKYO -- Japan's government is striving to strengthen its monitoring measures and beef up border controls to forestall the spread of coronavirus variants now appearing worldwide, but disease experts are expressing further concerns that the mutations could spark a fourth wave of infections.
Variant infection cases had been confirmed in 20 of Japan's 47 prefectures as of March 5, and the city of Kobe announced that it has detected variants in 15% of local positive coronavirus test samples. In some regions, there have been variant infection clusters.
"If the variant strains spread widely, it could become a 'fourth wave,'" said Atsuo Hamada, an infectious disease expert at Tokyo Medical University. "If the fourth wave of infections comes before the current 'third wave' dwindles, the medical system, which has finally begun to recover, may be pushed to the edge of collapse again. It's very important to delay the spread of the variant strains as much as we can."
The national government is strengthening monitoring of three variant strains originally detected in Britain, South Africa and Brazil, respectively; all of them said to be more infectious than the original virus, while also weakening immunity and vaccine efficacy. In Japan, 194 people, excluding those in airport quarantine, had been confirmed infected with variant strains as of March 5. Of these, 183 people had the British variant.
In January, there were just 24 new variant cases spread over four prefectures. That figure grew sharply in February, with new variant infections found in 20 prefectures, from Fukushima in the northeast to Kagoshima in the southwest. There have been a Japan-high of 40 new variant cases in Saitama Prefecture just north of Tokyo, including a pair of virus clusters at a child care center and a workplace. A cluster at a nursery school in the central prefecture of Niigata infected more than 30 people, including children and their family members.
An independent study by the city of Kobe revealed that 36 people were infected with variant strains between the end of January and Feb. 18. While the central government is asking public health institutes across Japan to conduct polymerase chain reaction (PCR) tests on 5% to 10% of people infected with the coronavirus to screen for variant strains, the Kobe Municipal Government has been screening some 60% of cases. The results showed that variants accounted for 15.2% of total infections between Feb. 12 and 18. The Tokyo Metropolitan Government, which has the highest number of coronavirus cases in the country, strengthened its testing system in February, and has apparently increased the ratio of variant screening tests from about 5% to about 10% of all cases.
"It's unthinkable that the variants have spread only in Kobe," Hamada said. "Probably a figure that's close to the truth has emerged as a result of the city's proactive testing." He added that he believes it highly likely that the variant strains have spread to a similar extent in the Tokyo metropolitan area as well as the Kansai region in the country's west.
"We must contain the variants by enhancing testing systems," Hamada warned.
At a March 3 meeting, the health ministry's infection prevention expert advisory board stated it was possible the variants would eventually replace the original coronavirus strain. If highly infectious variants spread, the number of cases may increase, badly stressing the medical system.
According to analysis of reports received by Feb. 25 by the National Institute of Infectious Diseases, 93% of people infected with variant strains in Japan had never been abroad. By age bracket, those younger than 10 years old accounted for 21% (31 children) of cases -- the highest ratio -- followed by those in their 30s (19%) and those in their 40s (17%). Though the possibility that the new strains are more infectious for children has been discussed abroad, Japan's health ministry said that "there is as yet no confirmed proof" that this is the case.
"Looking at this data alone, the ratio of children younger than 10 years old is certainly high, but we'd like to continue our analysis," said Takaji Wakita, director-general of the National Institute of Infectious Diseases. He added, "We need to determine whether the variants are truly highly infectious for children."
The British coronavirus variant cases have been confirmed in more than 90 countries and regions around the world. In response, the Japanese government on March 2 added 13 nations, including Germany and France, to its list of places where variant strains are spreading, and said it plans to strengthen border controls.
"The possibility of variant strains coming in from abroad will rise if the border controls are eased," Hamada said. "Strong border controls are necessary at least until the third wave blows over."
(Japanese original by Naomi Hayashi, Lifestyle and Medical News Department)