HTVL Retrovirus. Getty Images Credit: GARO/PHANIE

HTLV is a retrovirus that infects white blood cells (T-cells or lymphocytes) that fight infections. As many as 10-20 million people have the infection, but many do not know.

There are two types of HTLV, I and II. These viruses are related. At one point, another HIV that infected T-cells was labeled HTLV-III, but this was not accurate. Since then a new virus has been labeled HTLV-3.

HTLV-I is found often in the Caribbean and Japan, as well those with ancestry from South America, Australia, Africa, and the Middle East. In Japan, HTLV-1 can be found in about 1 in 100 blood donors, but in particularly affected areas, up to 1 in 10 over the age of 40.

There are clusters of the infection where rates are at least 1-2% but can reach up to 20-40% in people over 50 years, as the risk of infection increases with age. These areas are scattered over the globe - from the Caribbean, especially parts of Jamaica and Haiti, as well as parts of Colombia and French Guyana, to parts of central and western Africa and the Middle east particularly areas in Iran, as well as Romania, Japan, and among some Aboriginals in Australia. There have been some small clusters among African-Americans from the southern US as well as those of Afro-Caribbean descent in Brooklyn.

There are also pockets among IV drug users, such as in Louisiana.

HTLV-2 is found particularly among First Peoples, particularly Native Americans and Amerindians in Brazil as well as in Panama. Rates were as high as over 1 in 10 among individuals in some reservations in southern Florida and 1 in 100 in American Indians blood donors in New Mexico.

Why does this matter?

HTLV can be a silent infection, but for some, it can lead to some pretty serious medical problems. HTLV-1 can lead to cancer, muscle problems, and other infections. Most, however, will not have symptoms; maybe 1-4% will develop cancer, usually between the ages of 30-50 years after decades of infection.


Adult T-cell leukemia/lymphoma (ATL)  

The presentation can be acute, smoldering, or chronic - or, in other words, it may not come on suddenly but have a slow build up. There can be high levels of calcium in the blood, which can be very dangerous to the kidneys or a patient's mental state. There can be large lymph nodes (especially in the chest in the mediastinum), large livers and spleens, and bone lesions where the bone is broken down, there can also be skin, lung, and gastrointestinal tract involvement.

HTLV-1 Associated Myelopathy/tropical spastic paraparesis (HAM/TSP)

The disease is a Myelopathy which means the spinal cord is damaged by the disease. It can cause progressive weakness of muscles, especially in the legs. This may start between ages of 30-50 and rarely in children.

It usually begins with slow and gradual leg weakness and loss of sensation. This may feel like "pins and needles" - like your leg has fallen asleep. Some may have problems urinating and need to go frequently, some may have bowel problems or erectile dysfunction. Some have back pain and pain in their legs. Many have skin infections at the same time.

It can also be associated with eye inflammation or dry eyes (uveitis or keratoconjunctivitis sicca), joint pains (arthritis), lung inflammation (pulmonary lymphocytic alveolitis), and muscle weakness and inflammation (polymyositis).

Opportunistic Infections: Persons with HTLV-1 are prone to specific opportunistic infections. The worm Strongyloides is common worldwide; it can become a massive infection in persons with HTLV-1. It has also been found that the infection can be tied with infective dermatitis - skin infections, especially chronic eczema tied to Staphylococcus aureus and streptococcus.


The effects of HTLV-2 are less clear. It has been tied to a type of leukemia (hairy cell) but the risk is not clear.

How is HTLV transmitted?

  • vertically (from mother to child 5%, often through breastfeeding)
  • sexually
  • blood transfusion
  • sharing of needles and syringes

It is not spread by casual contact. It often spreads in families.


There is no vaccine, but there is work on finding a vaccine. There is no specific treatment or cure for the virus. The muscle disorder is treated symptomatically. The cancer, ATLL, is treated by cancer specialists with specific chemotherapy and potentially bone marrow transplants. Infections are treated with specific antimicrobials.

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