context: Cytomegalovirus ( CMV) is a common virus related to the herpes virus that gives you cold sores. Over half of adults in the U. S. have had it in their body by the time they turn 40. It's not a problem for most people because a healthy immune system can easily control it. But it can make people with weakened immune symptoms, like someone with advanced HIV, very sick. Most often, in persons with advanced HIV, CMV causes an eye infection called retinitis that can lead to blindness. CMV retinitis is an AIDS-defining condition. You probably won't catch CMV from casual contact, but it's possible to get it by touching your eyes, nose, or mouth after contact with an infected person's: Saliva Semen Vaginal fluids Blood Urine Breast milk You can also get cytomegalovirus through: Sexual contact Blood transfusions Organ transplants An infant can get it before birth, which usually happens when a woman gets CMV while pregnant, or through breastfeeding. Most healthy people who get CMV don't know it because it usually doesn't cause symptoms. If you have symptoms, they're mild and similar to other illnesses: Fatigue Swollen glands Fever In persons with advanced HIV, CMV can move around your body if it's not treated. You could have: Blind spots or moving black spots, called "floaters," in your eyesight Blurred vision Blindness Diarrhea Belly pain Painful or difficult swallowing Pain, weakness, or numbness at the base of your spine that makes walking a struggle In rare cases, CMV can also cause: Changes to your personality Headaches Trouble concentrating Shortness of breath Dry cough If you're HIV-positive, your chance of becoming sick with CMV is greatest when your CD4 count is below 100. There are tests to check your blood and urine to see if there's any trace of the virus. For example, a serologic test looks for antibodies that your immune system makes to fight CMV. Your doctor can do a biopsy -- taking tissue or fluid from your intestine, throat, or spine -- and look at it under a microscope, too. An eye doctor can check for inflammation in your retina. Imaging tests, like a CT scan, give your doctor a picture of your lungs or brain that can show changes caused by CMV. When you have retinitis caused by CMV, your doctor may give you very strong IV meds for a couple of weeks, a process called induction therapy. For daily treatment, you may have a catheter put into your chest. After a while, your doctor may switch you to pills. You might need medication injected directly into your eye if the virus is threatening your sight. Once the infection is under control, you'll take a pill each day to keep it at bay. Your doctor may prescribe drugs to keep the virus from making more copies of itself, including: Cidofovir ( Vistide) Foscarnet ( Foscavir) Ganciclovir ( Cytovene) Valganciclovir ( Valcyte) Symtuza, a combination of darunavir, cobicistat and TAF/ FTC, which is tenofovir alafenamide ( TAF) and emtricitabine ( FTC) These drugs generally can't cure the disease if you have advanced HIV, but they can control it while your HIV infection is being treated with antiretroviral therapy ( ART). You could have side effects, depending on which medicine you take, including: Low white-blood-cell count (neutropenia), which raises your chance for other infections Feeling tired from low red-blood-cell count (anemia) Getting queasy or throwing up Rash Lower testosterone levels Kidney problems Treatment for CMV is used less often now. This is because anti- HIV meds (antiretroviral therapy, ART), when given early in the course of HIV infection, will prevent progression to advanced HIV and will keep you from getting CMV disease in the first place. CMV was once the most common viral opportunistic infection linked to HIV. Now, correctly taking antiretroviral therapy ( ART) can help keep your CD4 count up and your immune system strong. It can also help stop retinitis from coming back. If you have advanced HIV, in addition to ART, your doctor might give you medicine to prevent CMV, but it's expensive, sometimes causes severe side effects, and may not work well. Whether you have advanced HIV or not, washyour hands often, especially after contact with others' urine or saliva. If you're around young children, avoid touching urine and saliva and things that come in contact with them because little kids are more likely to carry CMV via these body fluids. Use condoms when you have sex, including oral sex. Talk to your doctor about the likelihood of picking up CMV if you're going to get a blood transfusion.