Measles (Rubeola) Antibody Test, IgG and IgM

This test measures antibodies in your blood that your immune system makes in response to the measles virus. It helps determine whether you are immune to measles, have been vaccinated, or have a current or recent infection. Your doctor may order it if you have symptoms of measles, were exposed to someone with the disease, or need proof of immunity for work, school, or travel.

The Rickettsia conorii IgG and IgM test is a blood test that detects antibodies your immune system produces in response to Rickettsia conorii bacteria. This bacterium causes Mediterranean spotted fever (also known as boutonneuse fever), a disease transmitted through tick bites, particularly from dogs.

IgG and IgM are two types of antibodies, which are proteins your immune system produces to fight infections. IgM antibodies usually appear first, within a few days of infection, and suggest a recent or current measles infection. IgG antibodies develop later and stay in your body for years, showing that you are protected either from a past infection or from vaccination.

IgM antibodies are the first type your body produces when fighting a new infection. They typically appear within 1-2 weeks after being bitten by an infected tick and indicate a recent or current infection. IgG antibodies develop later, usually within 2-4 weeks after infection, and can remain in your blood for years, indicating past exposure or immunity to the disease.

The test is performed with a simple blood draw. A healthcare professional will clean your skin, place a band around your upper arm, and collect a small sample of blood from a vein, usually in your arm. The procedure takes only a few minutes, and you may feel a quick sting. Afterward, a small bandage is applied, and you can go about your normal activities.

A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where it is analyzed to detect the presence and levels of IgG and IgM antibodies against Rickettsia conorii.

A positive IgM result with or without IgG usually suggests a recent or active measles infection, and your doctor may recommend isolation and supportive care. A positive IgG result alone typically means you are immune to measles, either from past infection or vaccination. Negative results for both antibodies suggest you are not immune and may be at risk of infection if exposed. Your doctor will interpret your results together with your symptoms, vaccination history, and any known exposure.

Results are typically reported as positive or negative for IgG and IgM antibodies. A positive IgM result suggests you have a recent or active Mediterranean spotted fever infection. A positive IgG result indicates you have been exposed to the bacteria in the past. Both IgG and IgM positive may indicate an active infection. Negative results mean no antibodies were detected, but this could also mean the infection is too early to detect—your doctor may recommend repeat testing if symptoms persist.