You may know of Lyme’s Disease, but there are slew of funky things you probably haven’t heard of. Though not common sounding, these viruses can develop inside of you, or you bacteria can infect you unknowingly. Know what to look out for—from sources to symptoms.

Cytomegalovirus Antibodies: CMV’s a common virus, which may cause a mononuceosis-like illness in healthy people, or more severe disease in immunosuppressed people. The presence of CMV antibody indicates recent infection or exposure. Infection of healthy adults and children usually results in asymptomatic disease but can cause mononucleosis or hepatitis. In rare cases, it may result in chronic fatigue.

Epstein-Barr Virus Antibodies: EBV causes infectious mononucleosis. Infection with EBV’s common and occurs frequently in late adolescence or early adulthood. Once infected with the virus, individuals develop virus-specific antibodies. Some infected people develop chronic fatigue syndrome.

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Toxoplasmosis Titers: Toxoplasmosis is a common infectious disease caused by the parasite Toxoplasma gondii. You can become infected if you accidentally touch your hands to your mouth after cleaning a cat’s litter box, gardening or handling undercooked meat. It causes only mild symptoms or fatigue in healthy individuals.

Lyme Disease: Ticks carry this bacterial infection. This often causes an expanding, target-like skin rash, which is followed by fatigue, arthritis, malaise, nervous system problems and heart rhythm disturbances, several months later. Sometimes people with untreated Lyme disease develop persistent fatigue associated with aching joints and muscles, mood swings and memory problems. It’s worthwhile to learn if you’ve been infected, by measuring whether your antibodies have responded.