There are a lot of unknowns surrounding long COVID — the various long-term side effects experienced by a subset of people who who were infected by COVID-19 — and the spike in cases amid the Omicron version of coronavirus adds new questions as the pandemic nears its third year.

"Omicron is a very novel strain," Dr. Ellen Eaton, an associate professor at the University of Alabama at Birmingham’s Division of Infectious Disease, said on Yahoo Finance Live (video above). "We’re still learning how it’s going to infect individuals who are vaccinated, health care workers, unvaccinated, and also immunocompromised health care workers in our midst."

Eaton added that "we don't really know what Omicron is going to do in terms of long COVID. We’re seeing mild upper respiratory-type infections, colds in people who are fully vaccinated who have breakthrough infections. But we don’t know what they’ll look like in a month. Will they have fatigue? Will they have headaches? Will they have long COVID symptoms where they’re going to need more time off work?”

An estimated 15.7 million Americans are struggling with long COVID, according to the American Academy of Physical Medicine and Rehabilitation (AAPMR), which uses a model that assumes 30% of all COVID-19 surviving cases result in the chronic condition.

As of July 2021, long COVID is considered a disability under the Americans with Disabilities Act (ADA). Furthermore, even those who had mild symptoms or were asymptomatic have reported long-term effects.

“One thing that was surprising to us was the large percentage of asymptomatic patients that are in that category of long Covid,” Robin Gelburd, president of FAIR Health, a nonprofit organization that conducted a study of post-COVID health problems using a database of private health insurance claims, told the New York Times in June.

A study published in The Lancet in August looked at long COVID patients from 56 different countries, including the U.S., and found that 96% of the participants still had symptoms 90 days after testing positive. Most common symptoms involved fatigue, post-exertional malaise, and cognitive dysfunction. About 45% of those patients had to reduce their work schedule as a result while 22.3% had to stop working altogether.

"We need to start thinking of [COVID] as a systemic virus that may clear in some people, but in others may persist for weeks or months and produce long COVID — a multifaceted systemic disorder," Ziyad Al-Aly, director of the clinical epidemiology center at the Veterans Affairs St. Louis Health Care System, told Bloomberg.

Adriana Belmonte is a reporter and editor covering politics and health care policy for Yahoo Finance. You can follow her on Twitter @adrianambells and reach her at [email protected].

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