A sharp decline in the number of cases of influenza in the United States in the 2020-2021 season has been observed.
The peak time of the flu season in the United States is between December and February each year. Annually, the influenza illness causes a significant burden on the healthcare system of the United States. But this year, it has been observed that the usual influenza season did not manifest in the US. The figures from the Center for Disease Control and Prevention of the United States indicate that there have been only 2000 cases of flu this year since September. Usually, there have been around 206000 cases of influenza each year during the same time period.
Before this manifestation, scientists were fearing having to deal with both COVID-19 and the Flu in what some refer to as a twindemic. This meant that scientists were concerned about a national influenza outbreak along with the surge in the number of cases of COVID-19 and the impact of this double outbreak situation on the already burdened healthcare system. But due to the sharp decline in influenza cases, the current situation has provided much-needed relief for the healthcare system and the healthcare staff.
Why this record low number of COVID-19 cases?
This decline in the number of cases of influenza may have occurred due to the following reasons.
As the influenza virus is transmitted through respiratory droplets and the public health measures for COVID-19 like social distancing, wearing masks, and closure of public places were in place, so these measures may have helped in decreasing the transmission of the influenza virus.
The second reason can be that almost all the population of the United States has had previous exposures to various strains of the influenza virus and those exposures have created an immune response in the population. This built-up immunity might have played a positive role in decreasing susceptibility to developing the influenza virus this year.
According to experts, the surge in COVID-19 cases may have played a role in decreasing influenza cases because there is one dominant respiratory virus in a population at any given time.
Furthermore, the scientists have mentioned that this sharp decline in the 2020-2021 season cannot be attributed to the decreased number of testing for the flu illness as the number of tests performed for influenza illness has been higher than the previous year. Around 1.3 million tests have been performed for influenza illness this year while around 1 million tests for influenza are performed annually during this period of time.
When will influenza return?
Most scientists believe that the influenza virus will most definitely return. With the decline in the COVID-19 cases and the consequent relaxation in the public health measures in place for COVID-19, it is possible that the number of influenza cases will increase with the opening of schools, restaurants and other public places as the possibility and probability of transmission will definitely increase.
Experts believe that it cannot be easily predicted about the possible situation when the flu returns. The number of cases of the flu can increase upon its return as there has not been an exposure of the public to the newer strains of the flu virus and this situation can prove detrimental for the public as there would not be any immunity. On the other hand, it is believed that fewer cases of influenza mean that there would be lesser mutations of the virus. And it can be easier to control the virus once it manifests as there would be lesser strains to battle against.
The New York Times, The Flu vanished during COVID-19. What will its return look like? Accessed 24 April, 2o21, https://www.nytimes.com/interactive/2021/04/22/science/flu-season-coronavirus-pandemic.html
Center for Disease Control and Prevention, Weekly US influenza surveillance report, Accessed April 24, 2021, https://www.cdc.gov/flu/weekly/index.htm
Center for Disease Control and Prevention, Decreased Influenza activity during the COVID-19 Pandemic, Accessed April 24, 2021,