The study followed 113 patients at four different hospitals in Switzerland.
A new study in Science is shining a light on the continuing impact of long COVID, with research revealing further and continuing health concerns for some of the 16 million sufferers in the U.S.
The video is from a previous report.
Long COVID is a syndrome, or collection of symptoms, that continue or develop after an acute COVID-19 infection and can last weeks, months or years. There is no test to confirm if symptoms are related to long COVID. Some scientists suggest that long COVID is caused by overactive immune cells, but the exact cause remains unclear.
The study followed 113 patients at four different hospitals in Switzerland with mild and severe COVID-19 and found that 40 had symptoms of long COVID at six months, 22 of whom had persistent symptoms at 12 months.
Researchers looked at blood samples from the 40 who experienced long COVID symptoms, compared them to controls who were not infected with COVID-19, and found that those who had long COVID had evidence of inflammation (increased complement activity), blood cell dysregulation (hemolysis and platelet activation) and tissue injury in their blood.
The specific details from the small study may help provide "a basis for new diagnostic solutions," according to the researchers, for the condition with no known cure or FDA-approved treatments.
While these results finding evidence of inflammation in patients with long COVID symptoms are not entirely surprising nor specific to long COVID, they are a step forward in identifying the cause of long COVID.
It's more than just researchers, though, looking into developments in our understanding of the syndrome. The condition received renewed attention from the federal government last week, as the U.S. Senate Committee on Health, Education, Labor and Pensions convened a group of patients and experts to testify about the impacts of long COVID before a bipartisan group of Senators.
In the Senate's first-ever hearing on this topic, Sen. Tammy Baldwin said researchers and government officials need to "increase the sense of urgency" over understanding and treating the condition.
For Sen. Bernie Sanders, chairman of the committee, more needs to be done.
"We think we haven't done anywhere near enough, and we hope to turn that around," he said.
Medical experts testified at the hearing, telling the committee that the condition can emerge in patients of all ages and backgrounds, that the risk increases with multiple infections, and rates of long COVID are higher in minority communities.
"The burden of disease and disability from long COVID is on par with the burden of cancer and heart disease," Dr. Ziyad Al-Aly, M.D., a clinical epidemiologist at Washington University, said. "We must develop sustainable solutions to prevent repeated infections with SARS-CoV-2 and long COVID that would be embraced by the public."
Angela Meriquez Vazquez, a long COVID patient from California, testified that she has helped over 15,000 sufferers through online advocacy.
"We are living through the largest mass destabilizing event in modern history," she told the Senators.
As she told her own story, Meriquez Vazquez, a former runner, said she is currently on 12 medications. Although she said she has managed to continue working, and she has health care, the condition has forced her to work from home, lying down to minimize her symptoms.
"Not since the emergence of the AIDS pandemic has there been such an imperative for large-scale change in healthcare, public health, and inequitable structures that bring exceptional risks of illness, suffering, disability, and mortality," Meriquez Vazzque said.
One of the Senators -- Republican Roger Marshall -- shared his own testimony, revealing to the committee that one of his loved ones "is one of the 16 million people" who has "suffered for two years" with the condition.
He told the committee his family member's illness is "like mono(nucleosis) that does not go away," adding that the person has seen 30 doctors in an attempt to find help.
Marshall said there needs to be more focus on treatments for long COVID at the Centers for Disease Control and Prevention.
"I'm frustrated that our CDC is more focused on vaccines than they are on treatments," he said.
Dr. Al-Aly, while testifying, repeatedly called on our country's leaders and medical experts to come together to tackle the ongoing health crisis.
"We are the best nation on earth, and we can solve this," he said.
One of his proposed solutions is establishing a new multidisciplinary research institute to address infection-associated chronic conditions.
Research into the condition has been "slow," Dr. Charisse Madlock-Brown, Ph.D. from the University of Iowa, said at the hearing. She noted clinical trials are in the "experimental medicine" phase and pushed for more investment to identify proven treatments.
Sen. Tim Kaine said the National Institutes of Health has been provided more than $1 billion since 2020 to study long COVID, and he urged representatives from NIH to testify before the committee. In 2021, the NIH launched the Researching COVID to Enhance Recovery initiative to identify further risk factors and causes of long COVID.
"We can't take two years just to get 'geared up,'" he said.
According to the most recent information from the CDC, long COVID can cause up to 200 symptoms, including chronic fatigue, blood clots, gastrointestinal issues, brain fog and heart issues. Symptoms can last from months to years following a COVID infection. Risk factors for developing long COVID after a COVID-19 infection that have been identified include severe COVID-19 illness, underlying health conditions (such as asthma, diabetes, obesity or autoimmune diseases) and not getting the COVID-19 vaccine.
While the interest from the Senate and the new study in Science are promising, more research needs to be done to find the specific cause of why some people get long COVID from COVID-19, and others do not, and to find effective treatments.
Erin Hannon, MD, contributed to this report. Hannon is a resident physician in pediatrics from Columbia University/New York-Presbyterian Hospital, and a member of the ABC News Medical Unit.