Covid caution stifling other viruses
Rebound of flu, other ailments feared when measures end
Veteran virus trackers say they are chronicling something never before seen — the suppression of virtually every common respiratory and gastrointestinal virus besides the novel coronavirus. They theorize that is largely due to global shutdowns, mask-wearing and a host of other health protocols aimed at stemming the spread of the coronavirus.
These other viruses — including influenza A, influenza B, parainfluenza, norovirus, respiratory syncytial virus (RSV), human metapneumovirus — all appear to be circulating at or near levels lower than ever previously measured. The same is true for the respiratory bacteria that cause pertussis, better known as whooping cough, and pneumonia.
“It’s crazy,” said Lynnette Brammer, who leads the Center for Disease Control and Prevention’s Domestic Influenza Surveillance team. “This is my 30th flu season. I never would have expected to see flu activity this low.”
In 2019, during the third week of December, before the coronavirus struck the United States, the CDC’s network of clinical labs reported that 16.2% of the 29,578 samples tested were positive for influenza A. During the same week in 2020, the rate was 0.3%.
An online map of flu activity maintained by the CDC offers striking visual evidence of the effect. In 2020, for the week ending Dec. 19, the map of the United States is a sea of green, showing “minimal” levels in every state. For the corresponding week in 2019, most states were red (“high”) or deep blue (“very high”).
Another virus, enterovirus D68 — linked to a polio-like paralysis seen mostly in children — has likewise been greatly reduced. As recently as August, CDC officials warned doctors and parents to be on the lookout for cases of the polio-like condition, known as acute flaccid myelitis. Outbreaks of the condition have peaked in a peculiar every-other-year cycle for six years, with 120 cases across the United States in 2014, 153 in 2016, and 240 in 2018. But in 2020, the CDC confirmed just 29 cases.
“We haven’t had any specimen positive for [enterovirus] D68 … at our site in Colorado since July, and my colleagues around the country also saw very little,” said Kevin Messacar, a pediatric infectious-disease physician at Children’s Hospital Colorado in Aurora. “We also have not seen significant influenza or RSV on our wards in Colorado. All the most common childhood infections that land children in the hospital — influenza, croup, bronchiolitis — we are not seeing.”
As welcome as the absence of these other viruses is during a pandemic, epidemiologists say they see a potentially dangerous consequence after coronavirus cases eventually decline — a rebound that could be frightfully large given the relaxation of social distancing and lowered immunity to other pathogens.
The possibility of a rebound is not merely theoretical: It appears to be happening already in Australia. Official reports showed historically low levels of flu-like illness among children and adults beginning in May, usually the start of flu season in that hemisphere. The sharp decline in cases came as the country imposed strict shutdown measures. But in the past few months, after the coronavirus was virtually obliterated and the country ended those restrictions, the number of flu cases among children age 5 and younger began to soar, rising sixfold by December, when such cases are usually at their lowest.