As the nation suffered from a devastating winter wave of coronavirus cases, phones were sold at Old Dominion Pediatrics in Virginia. Callers with infected family members asked for advice on ways to quarantine at home so that others wouldn’t get sick.
But no one asked about the flu.
And the test results Eric Freeman saw showed that dozens of his patients had the coronavirus, but almost none of them tested positive for the flu.
“COVID has just been the dominant viral pathogen at this point, and it really hasn’t given the flu enough room to populate enough,” Freeman said in an interview Monday. “I haven’t had a quick flu test in my office since Thanksgiving.”
Public health experts, primary care physicians and pediatricians had warned for months that an increase in coronavirus cases during the winter months would be exacerbated by a typical flu season, which kills tens of thousands of Americans every year. But a funny thing happened in the midst of a global health pandemic: the flu season was effectively canceled.
Data from the Centers for Disease Control and Prevention (CDC) shows that only 1,893 Americans tested positive for the influenza virus this year, between clinical lab results and public health laboratories. Last year, more than 290,000 people had tested positive for flu at this point.
The CDC reported in August that 198 children had died from flu-related causes during the last flu season, a record high. Only one child has died so far this year, the lowest number since registration in 2004.
‘You would never think there would be a silver lining to this [pandemic], but this is about as close to a silver lining as it has been, ”said Peter Hotez, a pediatrician and dean of the National School of Tropical Medicine at Baylor College. “That’s what wearing masks and social distancing means and probably diminished personal lessons [does]
Less than 1 in 1,000 hospital admissions this year were for flu, one-seventh of those recorded during the last mild flu season in 2011-2012.
US health officials and vaccinologists typically pick up important clues about the coming flu season from viruses starting to circulate in the winter months in the Southern Hemisphere, our summer months.
But even when those officials raised the alarm about the potential for a dual season of respiratory illness, governments in Australia, Chile and South Africa reported lower-than-normal flu circulation. The viral curves in those three countries started to ebb much faster than in previous seasons, when new lockdowns and restrictions were introduced.
“No one has had a flu season for the past twelve months, with the exception of some countries in West Africa and some countries in Southeast Asia. And that’s in countries that are really tightly closed, it’s in countries that may not be that tightly closed. That confuses me a bit, ”said Richard Webby, director of the Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds at the St. Jude Children’s Research Hospital of the World Health Organization (WHO).
The same seems to be happening in the United States. Influenza is less transmissible than the SARS-CoV-2 virus that causes COVID-19, which means that masks and social detachment are likely to have an even greater impact on the overall flu rate than the coronavirus. School breaks meant curbing one of the most productive vectors of person-to-person transmission.
“Young children and schools play a huge role when it comes to flu transmission in the community,” Webby said. “With many schools not open or the controls actually taking place in schools, that has had a major impact on flu outbreaks.”
And, Freeman said, parents took to heart the warnings from public health officials that their kids should get a flu shot. While final data on the flu vaccine acceptance rate won’t be out in the coming months, Freeman said the vaccine acceptance rate in his practice, just south of Richmond, Virginia, was significantly higher than in previous years.
“This was one of the best years I’ve had in 15 years of influenza vaccination. This year the parents were absolutely engaged, very excited, ”said Freeman. “It was at a point where I couldn’t keep flu vaccines on my shelves.”
Seemingly, nothing about the coronavirus pandemic was easy, and some experts warned that even the least damaging flu season on record could have some drawbacks. A typical flu season provides clues as to the species that will become dominant next year, allowing vaccine manufacturers to tailor next year’s injection to a specific species. Without that knowledge, it can be more difficult to produce a vaccine that matches next year’s strain.
“There is not enough information about the circulating virus in the world,” said Adolfo Garcia-Sastre, director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine on Mount Sinai. “Because there is so little flu circulation, we don’t know exactly which strains, which variants are currently in circulation. This creates problems in the development of the vaccine and whether it needs to be updated or not. “
David Wentworth, chief of the virology, surveillance and diagnosis division of the CDC’s Influenza Division, said WHO’s Global Influenza Surveillance and Response System still tests between 50,000 and 100,000 samples per week to identify dominant strains.
“The reduced number of positive specimens made it more difficult to identify the optimal vaccine viruses for each of the four major groups of influenza viruses included in most influenza vaccines for the 2021-2022 influenza season, but it should be noted that the selection and recommendation process of vaccine virus is not based solely on flu viruses currently in circulation, ”Wentworth said in an email.
Identifying the next strain also relies on genetic sequencing of current strains, post-vaccination serological examinations to show which strains may break out next year, prognosis modeling and vaccine efficacy studies.
The lack of a spike in influenza infections reduced what could have been a crippling health care burden at the height of the pandemic, when more than 100,000 Americans were treated for COVID-19 in hospitals across the country. And the United States is still registering a large number of deaths caused by what the CDC calls flu-like illnesses – although in this case, the vast majority are due to COVID-19.
The flu is not going to go away, and health officials are constantly monitoring worrying tensions that could become the next threat to human health – the WHO said in January that it is in keeps an eye. H1N2 in Brazil and H3N2 in a child in Wisconsin.
But the success of controlling flu this year, doctors hope, will lead to more acceptance of the vaccine coming out in late summer and early fall.
“This one [mitigation] measures really work to reduce the spread of contagious viruses that cause the respiratory tract, ”said Garcia-Sastre. “I don’t think we will reduce the number of cases enough to completely prevent the spread of the virus.”