What makes a pandemic a pandemic?
When will the Covid pandemic no longer be considered a pandemic? Does it get downgraded to epidemic at some point? JB, Fullerton, California
Today’s Q&A is a lesson in the vocabulary of epidemiology, with some assistance from our regular expert on the subject, Katrine Wallace at University of Illinois at Chicago.
“Pandemic, epidemic and endemic are all terms used to describe level of disease spread,” Wallace says.
A disease reaches epidemic status when there are more cases of it over time than you’d normally expect in a given location. When there are epidemics in multiple places — potentially impacting large swaths of the global population — that’s a pandemic.
”A pandemic is typically caused by a situation where we have little or no immunity and a rapidly spreading disease,” Wallace says. That could be a new disease (like Covid), or one that has mutated to become more contagious. It could also be a disease that’s made a comeback after a period of control.
Endemic diseases are those that stick around.
“An epidemic disease level could be downgraded to an endemic level in a population if the number of new cases becomes consistently present, as expected in the population without significant fluctuations,” Wallace says.
The real question, then, is whether — or when — Covid will be considered endemic.
Though fewer people are getting sick than a year ago, there’s still a significant amount of Covid transmission. The virus also hasn’t established a clear seasonal pattern, like we see with influenza.
“These things make it difficult to know exactly what that ‘expected’ level of disease will eventually be,” Wallace says. “Also, the risk of (sometimes serious) post-viral complications exists with Covid, and we don’t have that risk with other respiratory viruses.”
When Covid establishes a more predictable rhythm, health officials can better prepare for outbreaks because they’ll know when to distribute vaccinations and take other measures. Recently President Joe Biden announced we’re moving toward a single annual Covid booster, though we’re still getting a sense of whether that matches the behavior of the disease.
“It definitely remains to be seen what additional tricks the virus has in store for us,” Wallace says. — Kristen V. Brown