Ask an infectious expert about the upcoming flu season and how it may affect or be affected by COVID-19, and the word you are likely to hear is “uncertain.”
First, the flu is always unpredictable, they say. Influenza activity and severity depend to a large extent on circulating virus strains and how well the vaccine strains selected before each flu season correspond to the circulating strains.
“Sometimes we do well, and sometimes we do not do so well,” said Jeanne Marrazzo, MD, MPH, director of the Department of Infectious Diseases at the University of Alabama in Birmingham, recently during an Infectious Disease Society of America (IDSA) ) briefing.
The virulence of the circulating strains, transmission dynamics, pre-existing population immunity and the age groups most prone to infection also play a role in the number of people who become ill with influenza each year. Since 201
But in this pandemic year, the coronavirus pandemic is adding a whole new layer of unpredictability.
Two scenarios emerge
“The big concern this year, of course, is that we need to see what can be a perfect storm of accelerated COVID-19 activity when people gather more inside, especially when they are constantly tired of wearing the mask, social distancing and hand hygiene. , and as they are exposed to seasonal flu, ”Marrazzo said.
The “perfect storm” could lead to the country’s hospitals being stretched to capacity as both influenza patients and those infected with SARS-CoV-2 (the virus that causes COVID-19) seek care. This is a scenario that the Center for Infectious Disease Research and Policy Director Michael Osterholm, PhD, MPH, and Ed Belongia, MD, director of the Center for Clinical Epidemiology and Population Health at the Marshfield Clinic Research Institute, wrote about earlier this year in an editorial Article. to Science.
“A large proportion of the population remains susceptible to SARS-CoV-2, and hospital stress will be greatest if COVID-19 and influenza epidemics overlap and reach their highest level around the same time,” they wrote.
But there is also a scenario where efforts to reduce the spread of coronavirus – such as physical distance, masking and better hand hygiene – help keep the flu at bay.
“There are many variables and it can go many ways,” Pritish Tosh, MD, an infectious disease specialist at the Mayo Clinic in Rochester, Minnesota, told CIDRAP News.
The second scenario could explain the low number of flu cases reported in countries in the southern hemisphere, where the flu season begins in April and ends in September.
According to the Australian Government’s latest surveillance report on influenza, influenza and influenza-like activity (ILI) is lower than average across all systems, and given the low number of laboratory-confirmed cases, there has been “minimal impact on society” due to influenza. Health officials in South Africa say the country basically skipped flu season. Countries in South America, including Brazil, Chile and Argentina, have all reported a lower number of flu cases than usual.
“One can only imagine that a great deal of this reduction has to do with what we do to reduce the transmission risk with COVID-19,” said Leonard Mermel, DO, ScM, professor of medicine at Brown University, under IDSA. briefing. “If you mask, you stay home, you avoid large crowds, you do not get to work when you are sick, some of the things that happen with COVID-19 will knock down the transmission risk from the flu.”
But Mermel said we can not “put all our hopes” on it because Americans may not be as aware of physical distance and masking as people in these countries have been, a point repeated by Tosh.
“There is variable societal acceptance of this practice between different countries and within this country,” Tosh said.
Tosh pointed out that influenza numbers in the United States, particularly hospitalizations, dropped drastically at the end of the 2019-20 flu season, just as cases of coronavirus increased significantly. But it may have been because people avoided going to the emergency department and emergency clinics, and not because of a real drop in infections.
If flu activity in the country is at typical levels this season or higher, and it is accompanied by an increase in COVID-19 cases, a concern is that test capacity and supplies (such as cotton swabs and reagents) that have already been strained by the pandemic, could be overwhelmed.
As Mermel noted, the symptoms of influenza and COVID-19 – with the exception of anosmia (loss or loss of sense of smell) – are very similar, meaning clinicians may need to test for both influenza and SARS-CoV-2.
When flu is very prevalent in a typical flu season, Tosh explained, flu testing is performed primarily on people who are seriously ill or in need of hospitalization. But this season, both for treatment and for epidemiological reasons, clinicians and public health officials need to know who had the flu and who has a coronavirus infection.
“I think we’ll have to test someone for both COVID and the flu if they present to the healthcare system with flu-like illness, which of course complicates things, as there are already supply chain issues related to testing COVID,” Tosh said. “I think this could exacerbate an already stressed supply chain for testing for both influenza and COVID.”
“My concern is that the system could quickly become overwhelmed and that individual clinicians will be faced with many challenges trying to figure out how to get both of these tests done in a timely manner,” Marrazzo said.
Mermel said his hospital is currently looking at platforms that can perform rapid tests for both influenza and COVID-19.
“But if we run out of these tests … it’s going to be problematic,” he said. “We certainly need to have stocks of reagents and kits so that people on the front lines can distinguish between the two viruses, treat those to be treated for influenza, and also alert our public health officials if it is COVID-19 with regard to for quarantine and contact tracking.
Influenza vaccination more important than ever
In preparation for the upcoming flu season, influenza vaccine manufacturers have increased production by 15% by nearly 200 million doses to the United States. Pharmacies and doctors’ offices are introducing systems for physical distance. No matter how well this year’s flu shot matches the circulating strains, public health officials and infectious experts say flu vaccination will be extremely important this year.
“The flu vaccine works: it prevents hospitalizations, it prevents mortality, it prevents symptomatic disease,” Marrazzo said. “If there’s ever a year where you need to get your flu vaccine, get your kids vaccinated, this is the year because you really need every single protection you can get.”
“It is important to get it [the flu vaccine] every year, but the importance of getting it this year cannot be stressed [enough]said Tosh.
“Now is the time to stand up, get the vaccine and reduce the risk of these two life-threatening viruses infecting you at the same time or infecting your loved ones,” Mermel said.