CMV (cytomegalovirus) is a lifelong infection. Once you catch it, the virus never fully leaves your body. But the part most people care about, the period when you actually feel sick, typically lasts 2 to 4 weeks in healthy adults. Beyond that initial illness, CMV settles into a dormant state in your cells and stays there permanently, usually without causing any further problems unless your immune system becomes weakened.
How Long Symptoms Last in Healthy Adults
Most healthy people who catch CMV don’t even realize it. When symptoms do appear, they resemble a mild case of mono: fever, fatigue, sore throat, swollen glands, and body aches. This acute phase generally resolves within 2 to 4 weeks.
Fatigue is the symptom that tends to linger longest. Some people feel unusually tired for several additional weeks after the fever and other symptoms clear up. In uncommon cases, fatigue and general malaise can stretch to 6 months or longer, even in otherwise healthy individuals. There’s no reliable way to predict who will bounce back quickly and who will deal with prolonged tiredness.
How Long You Can Spread the Virus
Even after you feel better, your body continues shedding CMV in saliva, urine, and other bodily fluids. This shedding period is what makes CMV so easily transmitted, especially among young children in daycare settings.
Adults typically shed the virus for less than six months after their initial infection, though intermittent shedding in saliva and urine can occur on and off for the rest of a person’s life. Children shed the virus for much longer. In studies of infants born with CMV, the median duration of viral shedding in saliva was about 20 months. At 18 months of age, roughly 53% of these children were still shedding the virus. By age 4, that number dropped to under 10%.
Children with intermittent shedding patterns (virus detectable, then undetectable, then detectable again) shed for even longer, with a median of 30 months compared to 15 months for those with continuous shedding that simply stopped. This prolonged shedding in young children is one reason CMV spreads so easily in childcare environments and why pregnant women are often advised to wash hands carefully after changing diapers or handling toddlers’ saliva.
Why CMV Never Truly Goes Away
After the initial infection clears, CMV doesn’t get eliminated. It embeds itself in certain blood stem cells in your bone marrow, specifically a type of early-stage blood cell called CD34+ progenitor cells. The virus carries a set of genes that act like a molecular switch. One protein pushes the virus toward dormancy by blocking the normal development of the cells it hides in. Another protein can flip the switch the other direction, triggering the virus to wake up and start replicating again.
In people with healthy immune systems, the body keeps this reactivation in check. You may periodically shed small amounts of virus without ever knowing it. This is not the same as being sick. It’s more like the virus briefly stirring before your immune system puts it back to sleep.
CMV in People With Weakened Immune Systems
The picture changes dramatically when the immune system is compromised. This includes organ transplant recipients on immunosuppressive drugs, people undergoing chemotherapy, and those with advanced HIV.
In transplant recipients, CMV disease most commonly appears within the first 3 months after transplant if no preventive measures are taken. When patients receive preventive antiviral medication (typically for about 100 days post-transplant), the onset of CMV disease may be delayed but can still occur after the preventive course ends.
For people with HIV whose immune cell counts drop very low (below 50 cells per cubic millimeter), CMV can cause serious organ damage. The most common manifestation is retinitis, an infection of the retina that, left untreated, will spread across the entire retina within about 6 months and can cause blindness. CMV can also attack the digestive tract, lungs, and nervous system in severely immunocompromised individuals.
Treatment for active CMV disease in these populations involves antiviral medications given in two phases. The initial intensive phase runs 14 to 21 days for eye disease and 21 to 42 days for infections of the gut, lungs, or nervous system. After that, ongoing maintenance therapy continues until the immune system recovers enough to keep the virus suppressed on its own. Even after successful treatment and immune recovery, there’s still a small but real chance of relapse: about 3 in 100 people per year experience reactivation of eye disease even with relatively healthy immune cell counts.
How Long Antibodies Stay Detectable
If you’ve been tested for CMV, the timeline of your antibody results can be confusing. Your body produces two types of antibodies in response to CMV. IgM antibodies appear first during the acute infection, while IgG antibodies develop later and persist for life.
The tricky part is that CMV IgM antibodies can remain detectable for several months or even years after the initial infection. This means a positive IgM test doesn’t necessarily mean you were recently infected. It’s one reason doctors sometimes order an additional test called an IgG avidity test, which helps distinguish a recent infection from one that happened months or years ago. IgG antibodies, once they appear, remain positive permanently and simply indicate that you’ve been infected at some point in your life.
Congenital CMV in Newborns
Babies born with CMV (congenital CMV) face a different timeline. About 90% of these infants appear healthy at birth, but 10 to 15% of those seemingly healthy babies may develop hearing loss or other complications months or even years later. For the roughly 10% of babies who show symptoms at birth, such as small head size, liver problems, or hearing loss, some effects can be permanent.
Antiviral treatment for symptomatic newborns, when recommended, typically lasts 6 months. The goal is to reduce viral activity during a critical window of development, particularly to preserve hearing. Even with treatment, ongoing monitoring for hearing changes continues through early childhood, since CMV-related hearing loss can appear or worsen over time.