Mono virus, fat cells could play role in long COVID

A British historian, an Italian archaeologist and an American preschool teacher have never met in person, but they share a prominent pandemic bond.

Plagued by eerily similar symptoms, the three women are credited with describing, naming and helping bring long COVID into the public’s consciousness in early 2020.

Rachel Pope of Liverpool took to Twitter in late March 2020 to describe her bedeviling symptoms, then unnamed, after a coronavirus infection. Elisa Perego in Italy first used the term “long COVID” in a May tweet that year. Amy Watson in Portland, Oregon, got inspiration in naming her Facebook support group from the trucker cap she’d been wearing, and “long hauler” soon became part of the pandemic lexicon.

Nearly three years into the pandemic, scientists are still trying to figure out why some people get long COVID and why a small portion — including the three women — have lasting symptoms.

Millions of people worldwide have had long COVID, reporting various symptoms including fatigue, lung problems, and brain fog and other neurological symptoms. Evidence suggests most recover substantially within a year, but recent data shows that it has contributed to more than 3,500 U.S. deaths.

• Many studies and anecdotal evidence suggest that women are more likely than men to develop long COVID.

There could be biological reasons.

Women’s immune systems generally mount stronger reactions to viruses, bacteria, parasites and other germs, noted Sabra Klein, a Johns Hopkins professor who studies immunity.

Women are also much more likely than men to have autoimmune diseases, where the body mistakenly attacks its own healthy cells. Some scientists believe long COVID could result from an autoimmune response triggered by the virus.

Women’s bodies also tend to have more fat tissue and emerging research suggests the coronavirus may hide in fat after infection. Scientists also are studying whether women’s fluctuating hormone levels may increase the risks.

Another possible factor: Women are more likely than men to seek health care and often more attuned to changes in their bodies, Klein noted.

• Several studies suggest the ubiquitous Epstein-Barr virus could play a role in some cases of long COVID.

Inflammation caused by coronavirus infection can activate herpes viruses, which remain in the body after causing an acute infection, said Dr. Timothy Henrich, a virus expert at UC San Francisco.

Epstein-Barr virus is among the most common of these herpes viruses: An estimated 90% of the U.S. population has been infected with it. The virus can cause mononucleosis or symptoms that may be dismissed as a cold.

Henrich is among researchers who have found immune markers signaling Epstein-Barr reactivation in the blood of long COVID patients, particularly those with fatigue.

Not all long COVID patients have these markers. But it’s possible that Epstein-Barr is causing symptoms in those who do, although scientists say more study is needed.

• Obesity is a risk factor for severe COVID-19 infections and scientists are trying to understand why.

Stanford University researchers are among those who have found evidence that the coronavirus can infect fat cells. In a recent study, they found the virus and signs of inflammation in fat tissue taken from people who had died from COVID.

Lab tests showed that the virus can reproduce in fat tissue. That raises the possibility that fat tissue could serve as a “reservoir,” potentially fueling long COVID.

Could removing fat tissue treat or prevent some cases of long COVID? It’s a tantalizing question, but the research is preliminary, said Dr. Catherine Blish, a Stanford infectious diseases professor and a senior author of the study.

It has been estimated that about 30% of people infected with the coronavirus will develop long COVID, based on data from earlier in the pandemic.

Most people who have lingering, recurrent or new symptoms after infection will recover after about three months. Among those with symptoms at three months, about 15% will continue to have symptoms for at least nine more months, according to a recent study in the Journal of the American Medical Association.