Reduction in Seasonal From COVID-19 Prevention Measures

In February and March 2020, when coronavirus infectious disease-2019 (COVID-19) spread rapidly throughout Japan, it was the time of seasonal influenza infection. Is it possible to have these two infectious diseases at the same time? Influenza virus infection is common to the respiratory tract of cells on top of the from the nose to the larynx. On the other hand, the SARS-CoV-2 infects cells in the back of the lung in addition to the upper respiratory tract and causes pneumonia. These two infectious diseases are completely different diseases. Therefore, when both viruses are exposed to humans in a short period of time, it is highly conceivable that both viral infections will occur at the same time, as in the case reported in Wuhan. Hand washing is the basic protection against these viral infections.

This season (2019-2020), the National Institute of Infectious Diseases reported that the number of patients infected with the seasonal influenza virus in Japan was estimated to be about 7.3 million, or about 60% of those from 2018-2019. In the week when the epidemic of seasonal influenza infection reached its peak (December 23 to 29, last year), approximately 5,000 fixed-point medical institutions nationwide reported the lowest number of seasonal influenza cases in the last 12 years. In other words, the cumulative number of influenza cases nationwide in 2020 (estimated by the Ministry of Health, Labor and Welfare, as of March 29, 2020) decreased to about 40% of the same period of the previous year (about 10.64 million).

As seasonal influenza virus epidemics infect humans, two A-types and one B-type; total of three influenzas virus types have been reported. Different types of seasonal influenza viruses are prevalent each year. Often, two or three seasonal influenza viruses simultaneously spread. However, type A (H1N1) accounted for more than 90% of the influenza epidemics this season (2019-2020). In other words, almost one type of seasonal influenza virus was prevalent this season. This season, due to the influence of the SARS-CoV-2, people are thoroughly washing their hands and wearing masks. The protective actions against the viral infection are likely to have contributed to the reduction in the number of seasonal influenza patients.                      JAMA Published on August 2020 by Kyoto@Takuma H