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October typically marks the beginning of the flu season and it’s coming with new warnings of a possible “twindemic” of COVID-19 and influenza.
The United States and much of the world got a welcome break from the flu last year with fewer cases than any time in recent history. The coronavirus was spreading fast but pandemic mitigation measures like masking, social distancing and people going to school and working remotely left few opportunities for the flu virus to spread.
The U.S. may not likely be so lucky this year. According to researchers at the University of Pittsburgh Schools of the Health Sciences projections, there could be up to 20% more flu cases than a normal year, with the potential to see nearly twice the typical caseload. The Centers for Disease Control and Prevention estimate average annual flu cases are between 9 million and 45 million cases with 12,000 to 52,000 deaths.
In one preprint study, researchers explained low flu cases last year could lead to a “compensatory second season” this year, with young children especially at risk because of little to no prior immunity. Another study suggested hospitalizations could rise to 600,000 unless flu vaccine uptake increased significantly. In the year before the pandemic, there were 400,000 hospitalizations.
Dr. Mark Roberts, director of the Public Health Dynamics Laboratory at Pitt Public Health and an author on both studies, noted that just because a “twindemic” was avoided last year, doesn’t mean it’s impossible this year. “If anything, our models show that we should be more concerned this year about the possibility of a surge in COVID-19 hitting at the same time as a massive flu outbreak in areas of the country with low vaccination rates against both diseases,” he said.
The United States is coming out of a surge of COVID-19 cases related to the delta variant. Most forecasting models suggest weekly cases and deaths will continue to decline through November. The data is less certain beyond that, though some are predicting another surge around the holidays.
Experts are anticipating several challenges with the possible coincidence of flu and COVID-19. Both viruses share many symptoms, including fever, chills, cough, fatigue and difficulty breathing. That means health providers will have to administer multiple tests to make sure they’re treating the right virus.
The low incidence of flu last year also means providers are “in the dark” about how the two respiratory viruses might interact, explained Dr. Iahn Gonsenhauser, chief quality and patient safety officer at The Ohio State University Wexner Medical Center.
“The bigger complication is we don’t know what it looks like when people have flu after getting COVID. We don’t really know what it looks like to get flu and COVID,” he said. “Those scenarios could potentially cause significant complications that we’re just not aware of right now.”
Gonsenhauser said he expects a more “severe” flu season this year. He, along with scores of other medical providers and public health officials, urged people to get vaccinated against both flu and COVID-19 and continue mitigation measures like masking and social distancing when appropriate.
The flu shot has a strong safety profile and is recommended for infants as young as six months. All available COVID-19 vaccines have been proven safe and effective. The Pfizer vaccine is the only one available for children as young as 12. The CDC recently announced it was safe for people to get both shots at the same time.
Flu vaccination rates had been climbing in recent years before the pandemic, according to the CDC. In the 2019-2020 flu season, about 52% of all eligible people got vaccinated. That included nearly 64% of children under 18 and 70% of adults over 65. Children under 5 have among the highest rates of vaccination. School-age children are also typically hit with the first wave of flu transmission in a community.
Though many people skipped their flu shots last year, experts say now is the time to get the jab. The shots have been shown to prevent serious illness and hospitalization. Getting the flu vaccine can also reduce the likelihood of symptoms that could be confused with COVID-19. Public health authorities recommend getting the vaccine before the end of October.
Yet, there is a risk that flu vaccine uptake could lag behind previous years because of the heightened political environment around shots.
“I definitely think the conversations around vaccines, the vaccine hesitancy that we’re seeing, the vaccine refusal that we’re seeing will likely have an impact and will likely lead to more people questioning the flu vaccine this year than ever before,” said Gonsenhauser.
He further warned that people should not be “desensitized” to the flu by the experience with the pandemic. COVID-19 has killed more than 702,000 people in the United States since March 2020. But influenza is also a very serious disease that kills tens of thousands per year and puts hundreds of thousands in the hospital.
Leaders at the CDC and the National Foundation for Infectious Diseases are scheduled to present data from the last flu season at a Thursday news conference. They’re also expected to address changing public attitudes toward vaccination.