--- ---  # Do You Have Unexplained Symptoms? They Might Be Post-Viral by [Veronique Greenwood](https://time.com/author/veronique-greenwood/) ## Veronique Greenwood Mar 25, 2026 1:49 PM UTC  Olga Siletskaya—Getty Images by [Veronique Greenwood](https://time.com/author/veronique-greenwood/) ## Veronique Greenwood Mar 25, 2026 1:49 PM UTC The common wisdom about [catching a virus](https://time.com/7381668/why-some-people-are-crushed-by-common-colds/) is that in a few days—a few weeks, tops—everything will be back to normal. And in many cases, that’s true. But as the [flood of Long COVID cases](https://time.com/7292910/covid-symptoms-long-covid/) during the pandemic demonstrated, sometimes it can take much, much longer. Additionally, doctors and scientists are realizing that post-viral symptoms can be more subtle than the [crushing fatigue and brain fog](https://time.com/7160814/long-covid-kid-personal-essay/) commonly seen in Long COVID and other post-acute infection syndromes, as these conditions are known. You might even have had a conversation with your own physician about a perplexing symptom where the doctor, at a loss to explain it, pins it on some mystery virus from which you have long since recovered. With the rise of new tools in molecular biology, it’s becoming clear that viruses and other pathogens can remain in the body or otherwise affect its workings for a surprisingly long time. “Doctors often use this as a ‘get out of jail free’ card,” admits Dr. Chris Smith, a virologist at Addenbrooke’s Hospital in the U.K. and host of the [Naked Scientists](https://www.thenakedscientists.com/podcasts/naked-scientists-podcast) podcast. But, he continues, “we are beginning to realize that there is this whole world out there that we had absolutely no insight into.” ## Which viruses persist in your body? It’s been known for some time that certain viruses stick around. [Herpes virus](https://time.com/4092601/herpes-who/) moves into a host’s cells and never leaves. Epstein-Barr virus, which causes mononucleosis, is also a long-term tenant, and HIV is a life-long infection, though it’s manageable with drugs. But many other viruses that were thought to see themselves out swiftly might actually be staying, said Dr. Emma Thomson, a professor of infectious diseases at the University of Glasgow. A particularly chilling example, in her personal experience: Ebola virus. **Read More**: [_How Close are We to a Universal Vaccine for Respiratory Illnesses?_](https://time.com/7382892/universal-vaccine-respiratory-illnesses-research/) In 2015, Thomson treated [a Scottish nurse who had contracted Ebola](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2816%2930386-5/fulltext) in West Africa. Many months later, the nurse, who had recovered, had a seizure, developed a piercing headache, and was admitted to the hospital for meningitis. Thomson, who had recently learned that [Ebola could linger in recovered men’s semen](http://bbc.com/news/health-34530948), suggested that her doctor put on full protective gear before doing a lumbar puncture, and that was lucky indeed: “The cerebrospinal fluid was full of Ebola virus,” Thomson says. “Somehow the virus had managed to hide out in her central nervous system and then emerge.” This kind of viral lingering [may be behind some cases of Long COVID](https://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2824%2900171-3/fulltext), and perhaps behind other post-viral symptoms, like joint pain, that may come from continued immune system activation long after initial infection. “This is why my eyes are open to the fact that...viruses persist in certain situations, even in people who are otherwise completely fit and well,” Thomson says. Such lingering may in fact have [led to the evolution of new strains of SARS-CoV-2](https://pubmed.ncbi.nlm.nih.gov/33831372/), with viruses accumulating new mutations during a stay in an unwitting human host. “What we don't know is, is that happening with other viruses?” Thomson asks. “There hasn't been enough research in that area at all.” ## What long-term effects can viruses have? Even when a virus has been wiped out, the body doesn’t immediately recover from the immune system’s full-court press. “When you fight an infection, you make millions of cells. It's a bit like growing a new kidney in your blood and lymph nodes, all over the body, in a matter of days,” says Smith. “That takes a massive amount of energy.” Time is needed for a return to equilibrium, perhaps contributing to fatigue after the early part of an infection is past, and it may take longer in some people than others. Research has found that in those with Long COVID, [certain immune cells stay elevated for months longer](https://www.nature.com/articles/s41467-024-47720-8?fromPaywallRec=false) than in people without the condition, although the reasons for this are not clear. What’s more, while a given virus might seem to be centered on the nose, lungs, and throat, says Smith, it is now evident that the immune system is sending messages to tissues all over the body. **Read More**: [_What Anesthesia Does to the Brain, According to a New Study_](https://time.com/article/2026/03/23/anesthesia-drugs-surgery-affect-brain) “There's a whole constellation of changes that happen” in the body when you get sick, he continues. “So we can't really view an infection as an isolated thing in one part of the body anymore. If it's anywhere, it's everywhere.” That can account for why a sore knee or stomach upset with no other explanation might be labeled “post-viral” by a doctor. Sometimes, a virus [trips a switch that results in the immune system turning on the host](https://time.com/4209612/zika-guillain-barre-syndrome-cdc/), even after the invader has departed. In Guillain-Barré syndrome, a post-viral autoimmune process destroys nerves, in some cases causing paralysis. Coxsackievirus infection [can lead to the development of Type 1 diabetes](https://academic.oup.com/edrv/article/44/4/737/7072701), perhaps through an autoimmune reaction that destroys cells in the pancreas. And some people develop post-viral arthritis, [a swelling in joints without a clear cause,](https://www.medicalnewstoday.com/articles/post-viral-arthritis#causes) but which eventually resolves. One virus linked to this is [parvovirus B19](https://www.cdc.gov/parvovirus-b19/about/index.html), which commonly causes Fifth Disease in children. ## Can you prevent post-viral symptoms? Avoiding post-viral symptoms totally would mean avoiding viruses, which is practically impossible. But keeping an open mind and a healthy respect for the powers of viruses circulating among us isn’t a bad idea. They might affect us in more lasting ways than a few days of lethargy and snot. Do You Have Unexplained Symptoms? They Might Be Post-Viral ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/article/2026/03/25/post-viral-symptoms-common/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/article/2026/03/25/post-viral-symptoms-common/"},"headline":"Do You Have Unexplained Symptoms? They Might Be Post-Viral","datePublished":"2026-03-25T13:49:36.014Z","dateModified":"2026-05-13T06:52:25.691Z","description":"When symptoms defy an obvious explanation, they could be the result of a past virus.","url":"https://time.com/article/2026/03/25/post-viral-symptoms-common/","keywords":["Virus"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc452a504d74c0e30/69c2c21074a6cc17592ccaba/GettyImages-1301141558.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Veronique Greenwood","jobTitle":"","url":"https://time.com/author/veronique-greenwood/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc452a504d74c0e30/69c2c21074a6cc17592ccaba/GettyImages-1301141558.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"GettyImages-1301141558.jpg","caption":"","creditText":"Olga Siletskaya—Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/virus/","name":"Virus"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/article/2026/03/25/post-viral-symptoms-common/","name":"Do You Have Unexplained Symptoms? They Might Be Post-Viral"}}]}] ```