Covid-19 has become a chronic condition for tens of millions of people – and an expensive one, as well. Long Covid – a condition marked by lingering symptoms that can involve multiple bodily systems – has cost a cumulative $386 billion in lost wages, savings and medical expenses in the US alone as of January, according to one estimate. On Tuesday, the Biden administration announced that it was making long Covid a national priority. It unveiled a plan to accelerate efforts to prevent, treat and detect long Covid through a national interagency research action program. In February, the National Institutes of Health announced a $1.15 billion initiative to support research into the condition over four years. Much research is needed to find answers to all the questions about long Covid. There’s no cure or specific treatment; there’s not even a test for it. Scientists still don’t fully understand what the symptoms are, how long it lasts, or why some people get it and others don’t. They haven’t even settled on a name for it: long Covid, post-Covid, long haul, post-acute Covid or chronic Covid. The US Centers for Disease Control and Prevention defines long Covid as health problems that last four or more weeks after a Covid-19 infection. The World Health Organization definition adds that the symptoms should not be able to be explained by an alternative diagnosis. It’s unclear exactly how many people have long Covid. Estimates range from 5% to 80% of those who become infected with the coronavirus. The condition can affect people of all ages, genders, races and ethnicities. Some can develop long Covid after a mild infection or even after an infection with no symptoms at all. They may have symptoms for a short amount of time or for years. Scientists don’t fully agree what symptoms count as long Covid. The CDC’s list of physical symptoms includes difficulty breathing, fatigue, problems sleeping, cough, chest and stomach pain, headache, racing heart and other heart problems, high blood pressure, joint and muscle pain, a feeling of having pins and needles under the skin, fever, dizziness, rash, diarrhea, a changed menstrual cycle, type 2 diabetes, hair loss, rashes, blurry or double vision, and a continued loss of the sense of smell or taste. Long Covid can also cause problems with mental health. People report unexplained mood changes, brain fog or difficulty thinking, memory problems, difficulties with language and general cognition, and PTSD. Dozens of studies have also shown that long Covid patients report long-term depression and anxiety that they didn’t have before becoming infected. Others report psychosis and suicidal behavior. Some research has found that people with long Covid have opioid use disorder and problems with other drug use. Some studies suggest that the virus is associated with physical changes in the brain, and that may be what is causing some of these problems. Symptoms can come and go over time, according to the World Health Organization. They may be so extreme that they’re debilitating. As of July, the US government determined that long Covid could be considered a disability under the Americans with Disability Act. It’s not totally clear why long Covid develops. As the disease may affect any organ system, there could be multiple reasons. In some people, it may stem from the direct cell damage caused by Covid-19. For others, long-term problems like muscle weakness or cognitive issues may develop after they’re hospitalized for Covid-19 for an extended period of time. Symptoms may also linger because the immune system overreacts and fails to slow down after an infection clears. Scientists are working on drugs that could treat long Covid and on tests to diagnose it. Clinics to treat long Covid have popped up across the country, although the CDC says primary care physicians may also be able to help. Patient advocates suggest that some doctors have dismissed patient concerns as psychological rather than physical in nature. The CDC advises medical professionals to listen and validate a patient’s experience if they have long-term symptoms. It encourages doctors to be particularly sensitive to people in marginalized populations that have been disproportionately affected by Covid, as their long-term symptoms may be underdiagnosed. Doctors are also advised to partner with a patient to help them identify achievable goals in recovery. Patients may also be offered supportive care that can include physical or occupational therapy, mental health counseling, speech therapy or even breathing exercises. While in treatment, people may be asked to keep diaries and calendars to document changes in their symptoms, especially if something seems to trigger them. A study published in January says one thing that might help people with long Covid is to get vaccinated if they hadn’t already. It found that people who got the vaccine were 54% less likely to report headaches, 64% less likely to report fatigue and 68% less likely to report muscle pain than were the unvaccinated. The best way to avoid long Covid, doctors say, is to keep from catching Covid-19 in the first place. Some studies suggest that even with a breakthrough infection, the risk of long Covid is much lower for people who are fully vaccinated.