A flu vaccine shot is being administered in Tokyo's Shinjuku Ward on Oct. 9, 2021, as seen in this image provided by Navitas Clinic Shinjuku.
TOKYO -- Experts in Japan have been on the alert against the simultaneous spread of the coronavirus and seasonal influenza during this winter, which is expected to see a "sixth wave" of COVID-19 cases, in spite of last season's low levels of flu activity.
A sudden rise in both COVID-19 and flu patients would strain Japan's health care system and increase the burden on the field, and this may trigger a medical collapse. While flu outbreaks were not seen last winter, contrary to general expectations, specialists have shown concern over a potential double outbreak this season.
"It is necessary to make preparations, taking into account the flu outbreak in autumn and winter," read a recommendation by the Health, Labor and Welfare Ministry's advisory board in a document it released on Sept. 27.
The initial symptoms of COVID-19 and influenza are similar and difficult to distinguish from one another. If both flu and coronavirus patients flood medical institutions that have outpatient wards for people with fevers, it is possible that those on the ground will be overstrained and become unable to provide appropriate medical care.
In normal years, flu outbreaks tend to occur during winter. Coronavirus infections also peaked between late December 2020 and early January 2021 during the "third coronavirus wave." There have been reported cases of breakthrough infections -- in which people inoculated twice for the coronavirus still contract it -- and many experts have predicted a "sixth wave" will hit the country this winter.
However, it is difficult to foresee double outbreaks. Although experts cautioned against a simultaneous spread last winter as well, the number of flu cases was extremely small. In 2018 and 2019, over 250,000 weekly flu cases were reported during January and February, the time during which infections reach a peak in usual years. However, this number dropped to around 90,000 during the same period in 2020, and fell below 100 in 2021.
The low circulation of the flu was observed not just in Japan, but worldwide. The World Health Organization (WHO) stated in a document released in June that influenza cases decreased drastically on a global level, excluding some areas, from mid- to late 2020. A flu outbreak has not yet occurred in the southern hemisphere this year.
As for the reason behind the low circulation levels, the WHO raised multiple factors. Countermeasures against the coronavirus, including restrictions on movement and closures of national borders, as well as teleworking and other social distancing measures, appear to be one factor that was effective in curbing the spread of influenza. The WHO pointed out that the period when such anti-coronavirus measures were commenced is directly linked with the plunge in reported flu cases.
That the coronavirus is more transmissible than influenza, and that people were equipped with immunity against the flu, due to having been infected in the past, are believed to be among the reasons behind only transmission of the influenza virus having been curbed.
The WHO has also raised the possibility of a "viral interference" -- a phenomenon where an outbreak of one virus can inhibit the spread of another type of virus. There have been past cases of viral interference between outbreaks of influenza and respiratory syncytial viruses, as well as between influenza and rhinoviruses.
That being said, it is not guaranteed that a flu outbreak will not occur this season. The British government has predicted that the size of the flu outbreak this winter will be 1.5 times that of regular flu season. A group from Spain warned in a JAMA article in June that herd immunity against a certain pathogen will wane if the pathogen is not circulated, and this may lead to an early-stage occurrence of a large and serious outbreak spanning a long period of time.
(Japanese original by Yuki Ogawa, Lifestyle and Medical News Department)
Font Size S M L Print Timeline 0