This past week California reported its first couple of influenza cases. This raised some concern as influenza typically doesn’t hit California until December or January. The federal Centers for Disease Control and Prevention estimated that 35.5 million people contracted influenza during the 2018-2019 flu season. This resulted in 490,600 hospitalizations and 34,200 deaths last year, without COVID-19.

In the coming weeks you will start hearing the term “twindemic” to describe the phenomenon of influenza and COVID-19 circulating simultaneously. The world is just now slowly settling down from COVID-19. What happens as the two collide is unclear.

The medical community is mounting an aggressive flu vaccination program this year in light of twindemic concerns. A bad flu season could reverse progress we made during the spread of COVID-19.

Before the COVID-19 pandemic, only half of the U.S. population followed the advice of the medical community and received a flu vaccine last season. Although a COVID-19 vaccine promises to be on the horizon, the reality is to prepare for a flu season either without a COVID-19 vaccine or with limited vaccination administration as it will take a while to vaccinate the majority of the nation. The COVID-19 vaccination timeline is expected sometime in late October at the earliest.

Currently, the percentage of U.S. respiratory specimens submitted for flu testing is at a historic low. It is believed to be because of the widespread adoption of COVID-19 mitigation measures that have also helped reduce influenza spread. Typically, over 20% of respiratory specimens testing for influenza are positive according to the CDC. So far, 2.3% are positive.

Countries in the Southern Hemisphere experienced light flu activity because of COVID-19 mitigation strategies. The hope is that the Northern Hemisphere will be light as well. But there is much we don’t know.

Although sharp declines in influenza activity have been noted in both hemispheres, some of the decreased activity can also be attributed to decreased influenza testing. COVID-19 was the preferential test for patients with respiratory symptoms after the COVID-19 outbreak. While it is difficult to separate the impact that COVID-19 measures will have on the influenza season, it is still unclear if the season will be delayed or blunted.

Though there is optimism from this data, there is also the realization that even mild influenza activity coupled with mild circulating COVID-19 could potentially add up when impacting a community in unison.

The effectiveness of a flu vaccine ranges from 20% to 60% depending on how accurately scientists predict circulating strains each season. Effectiveness also varies from person to person depending on their health. Even if the vaccine doesn’t prevent the flu in all individuals, it still can make the illness less serious if infected. This year any reduction in the number of flu cases or severity could make a huge difference.

Another fear that the public is not privy to is the availability of tests. The same reagents used to test for COVID-19 by extracting DNA or RNA from samples is the same process for testing both influenza and COVID-19. Shortages of influenza tests because of overwhelming COVID-19 testing is a possibility.

No one wants to contract either disease. No one especially wants to get infected with both at the same time. Health officials are urging everyone to get vaccinated for influenza during the months of September and October this year. The hope is that flu vaccinations will climb to record numbers. If there was ever a year to get the flu shot, this is the year.