The National Institute of Infectious Diseases and other facilities said about 5,000 medical institutions nationwide reported a total of 47,346 flu cases in the week through October 1, up by around 12,000 from the previous week.
The average number of flu patients per institution stood at 9.57. Based on the data, health officials estimate that Japan had about 333,000 flu cases.
Institutions in Tokyo and 13 other prefectures each saw an average of over 10 cases during the same period, suggesting these places could face a major flu outbreak within the next four weeks.
Tokyo pediatric clinic crowded with patients
A pediatric clinic in Tokyo's Meguro Ward is seeing a large number of children with cold- or flu-like symptoms. Clinic staff said the numbers of such patients have been twice what they were around this time last year.
They said more patients have been testing positive for either influenza or COVID-19.
"This year is altogether different. We have to operate after our reception hours to handle all the patients," said clinic head Dr. Nihei Koichi.
Influenza vaccinations are in high demand. Nearly all available slots to receive them at the Meguro clinic this month have already been booked.
Tokyo faces shortages of medicines
Some pharmacies in Tokyo are experiencing shortages of drugs to treat coughs and fevers, as well as expectorant medicines. One pharmacist said they are "pretty much unavailable."
Arai Nobuyuki, a pharmacist in Tokyo's Shinagawa Ward, said drug makers have been juggling shipments of cough medication. Inventories of such items remain unstable, and he said, "there just isn't enough."
"The current strain of cold virus is the most severe ever, and almost no products are available to treat coughs. I would like to request medical institutions to prescribe drugs only to those who really need them," Arai said.
Toho University professor Tateda Kazuhiro, an expert on infectious diseases, said he is concerned about widespread drug shortages across Japan if the current situation remains unchanged.
"The government needs to take the initiative in establishing a system that can maintain a stable drug supply, as patients cannot afford to forgo taking these medicines," he said.
Winter could bring unprecedented flu outbreak
The Tokyo Metropolitan Government issued an advisory in late September about the possible spread of influenza, the earliest in the season it had ever done so since record-keeping began in 1999.
"In Japan, not many people have immunity against influenza as the precautions taken during the COVID-19 pandemic helped keep a lid on flu cases," Tateda said. "The flu is spreading as anti-infection measures such as face masks are gradually being eased."
Tateda warns that the rising influenza cases could mean Japan is on the cusp of an unprecedented outbreak in November and December, when flu season typically peaks.
Government calls on public to get vaccinated
Takemi Keizo, Japan's health minister, is calling on people who are vulnerable to serious illness to be prepared, and get vaccinated as early as possible.
Takemi received both a COVID-19 booster and a flu shot at a clinic in Tokyo on Tuesday.
"If a new variant of COVID-19 arises, infections of the virus and influenza would spread at the same time," the minister said.
Takemi said that the government has secured an adequate supply of the vaccines, and he will closely monitor individual cases to determine whether there are any distribution problems.