Human T-Cell Lymphotropic Virus Type I Infection

Human T-cell lymphotropic virus type I, also called HTLV-1, is a retrovirus that infects certain white blood cells called T-cells. These cells are part of your immune system and help protect your body from infections. Once HTLV-1 enters your body, it stays there for life and cannot be cured.

Most people with HTLV-1 never develop serious health problems. The virus can remain inactive for decades or even your entire lifetime. However, about 5 to 10 out of every 100 infected people will develop complications. These include adult T-cell leukemia or lymphoma, a rare blood cancer, or neurological conditions that affect movement and coordination.

HTLV-1 spreads through body fluids including blood, semen, and breast milk. You cannot get it from casual contact like hugging or sharing food. The virus is most common in certain regions including Japan, the Caribbean, South America, and parts of Africa. In the United States, rates are much lower but some people are at higher risk based on where they were born or their family background.

Most people with HTLV-1 infection have no symptoms for many years or their entire lives. The virus stays quiet in the body without causing noticeable problems.

• Muscle weakness in the legs that gradually gets worse over time
• Difficulty walking or problems with balance and coordination
• Bladder control problems or frequent urinary tract infections
• Constipation or other bowel function changes
• Lower back pain or stiffness in the legs
• Numbness or tingling in the feet and lower legs
• Unexplained weight loss or night sweats, if cancer develops
• Swollen lymph nodes or enlarged spleen, in cancer cases
• Skin rashes or lesions, particularly with T-cell lymphoma
• Frequent infections due to weakened immune function

Many people with HTLV-1 remain completely asymptomatic throughout their lives. Symptoms typically only appear in the small percentage who develop complications decades after initial infection.

HTLV-1 spreads through contact with infected body fluids. The most common way the virus passes from person to person is from mother to child during breastfeeding. This accounts for the majority of cases worldwide. The virus can also spread through sexual contact, sharing needles, or blood transfusions. In countries that screen the blood supply for HTLV-1, transfusion risk is very low.

Your risk is higher if you were born in regions where HTLV-1 is common, including parts of Japan, the Caribbean islands, Central and South America, Central Africa, and Melanesia. Having a mother who was infected increases your risk, especially if you were breastfed. Other risk factors include having multiple sexual partners, using injectable drugs, or receiving blood transfusions before screening became standard. Living with someone who has HTLV-1 also raises your risk over time through prolonged close contact.

HTLV-1 infection is diagnosed through blood tests that look for antibodies your immune system makes in response to the virus. The initial screening test detects HTLV-I and HTLV-II antibodies. If this test comes back positive, a confirmatory test is performed to verify the result and determine which type of HTLV you have. False positives can occur, so confirmation is important before making a diagnosis.

If you think you may have been exposed to HTLV-1, talk to your doctor about testing. This is specialized testing that requires specific lab work beyond routine panels. Your doctor can help you understand your risk factors and whether testing makes sense for your situation. Early detection allows for monitoring and helps prevent transmission to others, especially during pregnancy or through breastfeeding.

There is no cure for HTLV-1 infection, and no antiviral medications effectively eliminate the virus from your body. Treatment focuses on monitoring for complications and managing any conditions that develop.

• Regular medical monitoring to watch for signs of disease progression
• Avoid breastfeeding if you are infected to prevent passing the virus to your baby
• Use protection during sexual activity to reduce transmission risk
• Never share needles or personal items that may have blood on them
• Inform blood donation centers about your status to protect the blood supply
• Corticosteroids or other medications if neurological symptoms develop
• Chemotherapy or other cancer treatments if leukemia or lymphoma occurs
• Physical therapy to maintain mobility if walking problems develop
• Bladder and bowel management support for related complications
• Mental health support to help cope with a chronic infection diagnosis