While the spread of the new coronavirus continues, the number of influenza cases (estimated) this season was the lowest in the past five years.
Looking at patient estimates for the past five years, the highest 2017-2018 season was just over 14 million, while the 2019-2020 season has only 728.5 million at this point, with regular announcements ending on April 10, earlier than usual.
Although the situation of medical institutions and the number of examinations may differ from previous years, there were approximately 4.8 million fewer examinations than last season’s total, and approximately 4.5 million fewer than the same period last season (11.76 million).
The major feature of this season is that the number of patients did not increase significantly during the usual peak period.
The epidemic began early this season and remained higher than last season in the number of reports through December. However, there was little change from the end of the year to the beginning of the year, when the number of patients usually surges, and the number of reports in mid to late January was only about one-third of last year’s.
The weather conditions that reduced the number of patients in January may be due to the fact that it rained a lot in Tokyo and other areas around the Kanto region due to the warm winter trend.
As a rule of thumb for influenza virus activity, it is said that the lower the absolute humidity value, the more likely it is to spread.
To illustrate the change in absolute humidity this season, let’s take the example of Tokyo, where absolute humidity was much higher than last season, especially from the end of December to the end of January.
The warm winter season has made it easier for low pressure to pass through the Pacific side. As a result, January in Tokyo saw the driest sunshine hours in 17 years and precipitation exceeding 100 mm for the first time in 11 years, with few dry, sunny skies as in previous years, as well as changes in absolute humidity.
The anti-virus measures also work well.
Besides the weather conditions, there are also said to be new coronavirus countermeasures.
Since the first case of infection was confirmed in Japan on January 16, measures such as hand washing are being taken more thoroughly than usual. Such measures are common to the prevention of influenza, and there was no significant increase in the number of cases during the cold wave from February onwards, when the weather conditions became more prevalent. It seems to me that the efforts of the people of the country have paid off.
At this time, it is being reminded that basic measures such as hand washing and cough etiquette are important for infectious diseases such as influenza and the new coronavirus. I would like to continue to take measures against infection as a daily habit in the coming winter.