The threat of community spread of the omicron variant is on Japan’s doorstep now that cases have slipped through the initial virus testing at airports and it has reached beyond those quarantining at home or a government-designated facility.

A woman in her 20s tested positive for the omicron variant while she was quarantining at her home in Tokyo after arriving from Texas on Dec. 8. She initially tested negative at Narita Airport and was allowed to self-isolate for 14 days at her home because she was not traveling from a place judged to be an omicron hot spot. But she later developed a fever and is now isolating at a health care facility, the government has said.

What’s more concerning is that she did not abide by the rules that she pledged to follow after entry — namely, to not come into contact with others during the isolation period. That led to the case of a man in his 20s who visited the woman two times last week and then tested positive for omicron on Friday, marking the 35th case of the variant in Japan.

The man had developed a fever and a cough two days before attending a J. League Emperor’s Cup match at Todoroki Stadium in Kawasaki on Sunday, media reports have said, prompting authorities to scramble to reach out to about 80 people who sat near him at the game and at least 100 people who work on the same floor at his workplace.

On Thursday, the health ministry’s coronavirus advisory board urged the government to beef up protection measures at ports and airports and conduct PCR screening to detect variants for all COVID-19 cases, on the assumption that it will spread in the country sooner or later.

“We recommend that broad testing is carried out on individuals who come into contact and share the same space with people infected with the omicron variant, regardless of whether they wore a mask or the duration of contact,” Takaji Wakita, the head of the ministry’s advisory board said. “We need to prepare by making sufficient estimates of what kind of a burden it could place on the health care system.”

A quarantine official checks passengers' documentation at Narita Airport on Dec. 1. | KYODO
A quarantine official checks passengers’ documentation at Narita Airport on Dec. 1. | KYODO

So far, the government has denied that the latest cases are examples of community infection, saying they are closely monitored cases and are traceable even if they slipped through the initial testing at airports.

“As far as I know, there is a difference between domestically detected cases and community infection cases, and as long as they are traceable, it’s not community spread,” a senior government official said.

Tokyo Gov. Yuriko Koike also said that the case of the man would not be defined as a community infection.

In the U.S., community-acquired infections are defined as such when they occur in nonhospital settings.

Regardless of the cases’ categorizations, the risk of a community-acquired infection is on the rise, as omicron is feared to be replacing the delta variant as the dominant strain of the coronavirus.

A study led by researchers at the LKS Faculty of Medicine at the University of Hong Kong has found that the strain infects and multiplies 70 times faster in the bronchi than the delta variant and the original strain.

Meanwhile, another study led by scientists at the Rockefeller University in New York has shown that omicron is more prone to escape the antibodies produced after vaccination or an infection than previous variants, although it added that a booster shot would beef up the antibody response sufficiently to deliver a substantial increase in protection.

“The message remains clear: If you are unvaccinated, get vaccinated,” Dr. Anthony Fauci, the top U.S. infectious disease expert and a member of the White House coronavirus task force, told reporters Wednesday. “And particularly in the arena of omicron, if you are fully vaccinated, get your booster shot.”

The variant has spread to at least 77 countries since it was first reported in South Africa a little over three weeks ago. The Daiwa Institute of Research has projected that if omicron infections spread in Japan, it could cause economic damage of about ¥10 trillion in 2022 — equivalent to 1.8% of gross domestic product — assuming that it causes the same level of serious disease as the delta variant.

Information from Kyodo added. Staff writer Satoshi Sugiyama contributed to this report.

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