Cold and humidity are definitely important – scientists can make flu spread faster or slower in guinea pigs just by altering the temperature and humidity of their cages. But it can’t just be cold and humidity. But if it was just cold, you would expect flu to track temperature instead of seasonality. Alaska is colder in the summer than Florida in the winter, so you might expect more summer flu in Alaska than winter flu in Florida. But Alaska and Florida both have lots of flu in the winter and little flu in the summer.
(if it was just humidity, same argument, but change the place names to Arizona and Florida.)
It’s the same story with people being cramped indoors. Common-sensically, this has to be some of the story. But if it were the most important contributor, you would expect to see the opposite pattern in very hot areas, where nobody will go out during the summer but it’s pleasant and balmy in the winter. Yet I have never heard anyone claim that any winter diseases happen in summer in Arizona or Saudi Arabia or terrible places like that.
If it was just vitamin D…look, it’s not vitamin D. Nothing is ever vitamin D. People try so hard to attribute everything to vitamin D, and it never works. The most recent studies show it doesn’t prevent colds or flu, and I think the best available evidence shows it doesn’t prevent coronavirus either. African-Americans, who are all horrendously Vitamin D deficient, don’t get colds at a higher rate than other groups (they do get flu more, but they’re vaccinated less, so whatever).
Influenza is sweeping the University of Michigan’s Ann Arbor campus, with 528 cases diagnosed at the University Health Service since Oct. 6.
The outbreak is so sudden and large — 313 cases were identified the week of Nov. 8 alone and 37% of flu tests that week were positive — that it’s drawn the attention of federal health leaders.
Among those who’ve contracted flu at U-M this fall, 77% didn’t get a flu vaccine. The cases were identified as influenza A (H3N2), said Lindsey Mortenson, UHS medical director and acting executive director.
“While we often start to see some flu activity now, the size of this outbreak is unusual,” said Juan Luis Marquez, medical director at the Washtenaw County Health Department. “We’re grateful for the additional support of the CDC and our ongoing partnership with the university as we look more closely at the situation.”
The first big improvement in the U.S. was in child mortality in the early 20th century — public health measures helped all ages, but the youngest the most. Then antibiotics and more and more vaccines improved mortality across the board, with children and young adults getting the most benefits. Improved auto safety and more stringent drunk driving laws helped all ages, but young adults the most (because they were the most idiotic drivers). We’ve seen improvements in middle age into old age due to reduced smoking and improved medical treatments — people who used to get their first heart attack in their 50s now see their first heart attack in their 70s… and it’s a lot less fatal now. And we’ve had amazing improvement in mortality at older ages.
It is very tempting to write a book about all the mortality trends we’ve got going on. The CDC has the data. They’ve issued reports on it. But few people really want to think about death. I’ll add it to my ever-expanding list of project ideas… (hey, Actuarial News was an idea for me for over a year… and now it’s here!)
Some 136 people were hospitalized for the flu between Oct. 1, 2020, and Jan. 16, 2021, and there were 292 deaths involving influenza during that period, the CDC reported. One child has died.
The flu season is far from over — it usually begins in the fall, and peaks between December and February.
But in comparison, 400,000 people were hospitalized for the flu and 22,000 died, including 434 children, during the entire 2019–2020 season, which the CDC described as “severe” for kids 4 years old and younger, and for adults 18-49 years old.
With coronavirus cases soaring in late summer, experts warned about the potential for a so-called “twin-demic,” which they said would’ve seen hospital systems overwhelmed by both COVID-19 and the influx of flu patients, but the surge never came. In fact, the Centers for Disease Control and Prevention (CDC), is reporting that flu activity in the U.S. “remains lower than usual for this time of year,” which is typically the peak of illnesses.
Since Oct. 1, 2020, or the start of flu season, there have been 165-laboratory confirmed flu-related hospitalizations in the U.S. According to the CDC, not only is this below average for this point in the season, it’s the lowest rate seen since data collection began in 2005.
So why did the influenza virus take a backseat to coronavirus? Experts say it’s a mix of factors, but mitigation measures put in place to stop the spread of COVID-19 likely played a big part.
During the months preceding the surge of SARS-CoV-2 infections this fall and winter, many public health officials expressed concern about the potential for a “double-barreled” respiratory virus season. In this scenario, healthcare facilities would be totally overwhelmed by: 1) patients afflicted by infections caused by endemic respiratory viruses (such as influenza) that occur during any normal year, and 2) a massive influx of coronavirus patients. Fortunately, such a catastrophe did not come to pass. The reason for this is an unprecedented reduction in flu prevalence for the 2020–21 season.
So perhaps a biological process, whereby viruses engage in some form of competition, or interactions, can better explain disappearances such as those currently being observed.
Subsequent research has borne out real world examples related to the phenomenon described by Simpson. According to a group of researchers at Yale, it is likely that a 2009 autumn rhinovirus epidemic interrupted the spread of influenza. The authors of that study write: “one respiratory virus can block infection with another through stimulation of antiviral defenses in the airway mucosa”. Results from another study, conducted in mice, support those findings. Mice were infected with either a rhinovirus or a murine coronavirus, and it was found that both attenuated influenza disease. Moreover, it was observed that the murine coronavirus infection reduced early replication of the influenza virus. In another study, negative interactions between noninfluenza and influenza viruses were suggested. According to the authors: “when multiple pathogens cocirculate this can lead to competitive or cooperative forms of pathogen–pathogen interactions. It is believed that such interactions occur among cold and flu viruses”. A recently published study examining the effects of interactions between an adenovirus and influenza in mice suggested that certain respiratory infections could impede “other viruses’ activities within the respiratory tract without attacking unrelated viruses directly”. Finally, in a paper entitled “A systematic approach to virus–virus interactions”, the authors state: “increasing evidence suggests that virus–virus interactions are common and may be critical to understanding viral pathogenesis”.
Federal flu maps use a traffic-light color scheme — green when flu is low, yellow when it’s medium and red when it’s high. Here in Massachusetts and around the country, the maps would normally show plenty of yellow and red by February. But this year they’re pure green.
And it’s not just flu that’s low. Dr. Eileen Costello, the chief of ambulatory pediatrics at Boston Medical Center, says it’s other viruses as well.
“We have seen dramatically reduced rates of influenza this year and respiratory synctitial virus, which is a viral infection of infants and very young children that we see,” she says. “It’s the meat and potatoes of every pediatric practice in America, and we’re not seeing it at all this year.