HTLV-1/2

HTLV-1 and HTLV-2 (human T-cell lymphotropic virus) are retroviruses that infect certain white blood cells (T cells) and remain in the body for life. They are passed on through sex, through blood (shared needles, blood transfusion or transplantation) and from mother to child, mainly through breastfeeding. This test measures antibodies against both viruses. It is a screening test: a positive result must be confirmed with a second test, which also shows whether it is HTLV-1 or HTLV-2.

• An infection (carriership) with HTLV-1 or HTLV-2, usually without symptoms
• With symptoms: a possible cause of slowly increasing stiffness and weakness of the legs (HTLV-1-associated myelopathy, HAM/TSP) or of inflammation in the eye (uveitis)
• Rarely: a type of blood cancer (adult T-cell leukemia/lymphoma, ATL) in people with HTLV-1

With a positive result, a confirmation test follows, usually through an infectious disease specialist. With a confirmed infection, the GP refers to an infectious disease specialist for explanation and monitoring, and with leg symptoms to a neurologist; advice covers condom use, not donating blood or organs and, for mothers, advising against breastfeeding. HTLV is not notifiable in the Netherlands.

According to the WHO, no single test can establish an HTLV infection on its own. The diagnosis is based on an antibody test like this one, followed by a confirmation test: an immunoblot or line assay, or a PCR on viral DNA in white blood cells. This confirmation also distinguishes between HTLV-1 and HTLV-2. In people without risk factors, a positive screening test relatively often cannot be confirmed.

• A positive screening test must always be confirmed with a second test; without confirmation it is not a diagnosis.
• The screening test does not distinguish between HTLV-1 and HTLV-2.
• Shortly after an infection, antibodies cannot yet be detected.
• The result does not say whether someone will ever get symptoms or a disease from the virus.

Worldwide, an estimated 5 to 10 million people live with HTLV-1. The virus is common in, among other places, Japan, the Caribbean, South America, large parts of Africa and Iran, and is rare in the rest of Europe. In the Netherlands, it is mainly seen in people who themselves, or whose mother, come from such an area, such as Suriname and the Caribbean islands; reliable figures for the Netherlands are lacking.

Useful if you, your mother or a sexual partner come from an area where HTLV-1 is common, especially with a wish to have children or a pregnancy, because the virus can be passed on through breastfeeding, and after sharing needles. Also with symptoms that may fit the virus, such as slowly increasing stiffness or weakness of the legs or an unexplained eye inflammation. In people without such a background or risk, the chance of an infection is very small and a positive screening test more often cannot be confirmed.

• A confirmed infection is lasting and cannot be treated; this can cause a lot of worry, even though most carriers never get symptoms.
• A positive screening test that is later not confirmed can cause needless worry.

• WHO: Human T-lymphotropic virus-1 (factsheet)
• UK Health Security Agency: Human T-cell lymphotropic virus (HTLV) types 1 and 2
• Adriani KS, Van Gorp ECM, Van Tienen C. Het humaan T-cellymfotroop virus type 1: een vergeten ziekteverwekker. Ned Tijdschr Geneeskd 2020;164