Influenza cases appears to have disappeared in some US cities amid COVID-19 pandemic
The flu has virtually disappeared from the US, with reports coming in at far lower levels than anything seen in decades.
- Measures put in place to battle the pandemic are a big factor in preventing a so-called “twindemic” of flu and COVID-19
- It could also be that COVID-19 has essentially muscled influenza aside
- Some US hospitals are yet to report any cases of influenza, despite February usually being peak season for the flu
Experts said measures put in place to fend off coronavirus — mask wearing, social distancing and virtual schooling — were a big factor in preventing a so-called “twindemic” of influenza and COVID-19.
A push to get more people vaccinated against the flu probably helped, as did fewer people travelling, they said.
Another possible explanation was that COVID-19 has essentially muscled influenza aside, along with other bugs that were more common in autumn and winter in the US.
Scientists don’t fully understand the mechanism behind that, but it would be consistent with patterns seen when certain flu strains predominate over others, said Dr Arnold Monto, a flu expert at the University of Michigan.
“This is the lowest flu season [the US has] had on record,” according to a surveillance system that is about 25 years old, said Lynnette Brammer from the US Centers for Disease Control and Prevention.
Hospitals said the usual steady stream of flu-stricken patients never materialised.
Dr Nate Mick, the head of the emergency department at Maine Medical Center in Portland, the state’s largest hospital, said: “I have seen zero documented flu cases this winter.”
It was the same in Oregon’s capital city, where the outpatient respiratory clinics affiliated with Salem Hospital had not seen any confirmed flu cases.
The numbers are astonishing considering flu has long been the nation’s biggest infectious disease threat.
In recent years, it has been blamed for 600,000 to 800,000 annual hospitalisations and 50,000 to 60,000 deaths.
Across the globe, flu activity has been at very low levels in China, Europe and elsewhere in the Northern Hemisphere.
And that follows reports of little flu in South Africa, Australia and other countries during the Southern Hemisphere’s winter months of May through August.
The story, of course, has been different with coronavirus, which has killed more than 500,000 people in the United States.
COVID-19 cases and deaths reached new heights in December and January, before beginning a recent decline.
Flu-related hospitalisations, however, were a small fraction of where they would stand during even a very mild season, said Dr Brammer, overseeing the CDC’s tracking of the virus.
Flu death data for the whole US population is hard to compile quickly, but CDC officials keep a running count of the deaths of children.
One paediatric flu death has been reported so far this season, compared with 92 reported at the same point in last year’s flu season.
Some doctors say they have even stopped sending specimens for testing, because they don’t think flu is present. Nevertheless, many labs are using a CDC-developed “multiplex test” that checks specimens for both the coronavirus and flu, Dr Brammer said.
More than 190 million flu vaccine doses were distributed this season, but the number of infections was so low that it was difficult for the CDC to do its annual calculation of how well the vaccine was working, said Dr Brammer.
A lack of data was also challenging the planning of next season’s flu vaccine. Such work usually starts with checking which flu strains are circulating around the world and predicting which of them will likely predominate in the year ahead.
“But there’s not a lot of (flu) viruses to look at,” Dr Brammer said.