Photo/Illutration Takaji Wakita, chairman of the health ministry’s advisory panel on anti-infection measures, holds a news conference after a meeting in Tokyo on Dec. 8. (Kai Ichino)

Japan’s fourth Omicron variant case was confirmed on Dec. 8 as health experts called for stronger measures to prevent a spread of novel coronavirus infections during the year-end holiday period.

A man in his 50s who arrived at Narita Airport on Dec. 4 from Nigeria via Qatar tested positive for COVID-19 after he landed.

Genome sequencing at the National Institute of Infectious Diseases confirmed that he was infected with the Omicron variant, the health ministry said.

He was taken to a medical institution on Dec. 8 but showed no symptoms of the disease, a health official said.

He received Pfizer vaccine shots on Oct. 1 and Oct. 22.

The 103 other passengers on the same flight tested negative upon their arrival at the airport, and 96 of them have been staying at their homes.

But the ministry now designates all passengers on flights with an Omicron-infected individual as those in “close contact.”

The ministry will inform the municipalities where the 103 passengers are located. They will be asked to stay isolated in accommodation facilities.

The ministry will also contact the passengers for health and location checks via smartphone apps.

The Omicron variant was a topic of discussion at a meeting of the health ministry’s advisory panel on COVID-19 measures on Dec. 8.

Experts on the panel expressed concerns that Omicron could be more infectious than previous variants and more resistant to the efficacy of vaccines, raising the risk of reinfections.

The panel asked the government to consider taking measures based on the assumption that Omicron infections would soon be found outside of quarantine stations.

All four confirmed Omicron patients in Japan tested positive at airport quarantine checks.

Although the number of infections in Japan has been at the lowest level since summer 2020, the panel noted a recent rise in the figures.

According to health ministry documents, the overall number of new infection cases per 100,000 people for the week through Dec. 7 was 0.60, up 11 percent from the previous week.

Gunma Prefecture, where cluster infections have occurred, had the highest number, at 4.13, followed by Yamagata Prefecture at 3.75.

Tokyo’s number per 100,000 people was 0.79, while Osaka Prefecture recorded 1.07.

Seventeen prefectures logged zero new infections over the week.

However, the advisory panel said more people are expected to attend year-end parties and other festive events later this month.

“When you go out to eat and drink, please choose restaurants or bars that are certified by prefectural governments (as taking anti-infection measures) and wear facial masks except when you eat or drink,” a health expert said.

The panel said people should avoid high-risk places and refrain from crossing prefectural borders for homecoming or other trips if they are showing symptoms, such as a fever.

(This article was written by Kai Ichino and Kayoko Geji.)