A Korea University College of Medicine research team said it has discovered that extensive Non-Pharmaceutical Interventions (NPI) against Covid-19, including social distancing and mask-wearing, helped to control influenza, too.

NPIs include actions to mitigate the spread of respiratory viruses, including personal protective measures such as hand hygiene and community measures of school closures and social distancing.

In the study, the research team led by Professor Kim Woo-joo found that the influenza epidemic period from 2019 to 2020 was exceptionally short, and the peak was also lower than those of previous years.

The influenza epidemic period announced by the Korea Centers for Disease Control and Prevention was between Nov. 15, 2019, and March 27, 2020. The influenza epidemic lasted 19 weeks and one day, which was six to 12 weeks shorter than those of previous years.

Figure 1 shows the influenza-like illness rate of flu seasons since 2016 and the number of Covid-19 cases.

In the graphic, Figure 1 shows that the influenza-like illness (ILI) rate decreased rapidly by the fourth week of the epidemic period. The ILI rate dropped down from 40.9 in week four to 16.4 in week six.

That period coincided with when Korea reported its first Covid-19 patient on Jan. 20 and developed widespread infection throughout the nation.

Figure 2 shows the detection rate of influenza viruses for flu seasons since 2016.

The detection rate of influenza viruses by the Korea Influenza and Respiratory Viruses Surveillance System (Figure 2) also rapidly declined from the fifth week of the epidemic period.

Hong Kong also saw a similar pattern of reduction in influenza infection. Hong Kong’s public health authorities estimated a 44 percent decrease in influenza transmission in the special administrative region in early February 2020 after the implementation of social distancing measures and changes in the public’s behaviors to control the spread of Covid-19.

The table shows the influenza epidemic with criteria, period, duration, and circulating influenza viruses for flu seasons since 2016.

“Influenza viruses have rarely been circulating in the spring of 2020. Many factors could have affected the size and length of the influenza epidemic. Still, the extensive application of NPIs, including mask-wearing and social distancing, in response to COVID-19 seemed to be a major factor behind the reduced influenza epidemic,” the research team said.

Social distancing measures with high feasibility and acceptability should be introduced even if vaccines for the Covid-19 virus become available in the future, it added.

shim531@docdocdoc.co.kr

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