HTLV-1 is a type of human immunodeficiency virus. It causes no symptoms in a vast majority of infected people. However, it can lead to serious illnesses in some.

What is HTLV-1?

HTLV-1 is a virus that infects T-cells, a type of white blood cell that forms part of the immune system. HTLV is also known as human T-cell lymphotropic virus.

HTLV-1 is one of the same type of viruses as HIV-1 and HIV-2 that cause AIDS. HTLV-1 does not cause AIDS, but it is spread in the same way.

Between 5 million and 20 million people throughout the world are infected with HTLV-1. Infection is most common in parts of southern Japan, the Caribbean, sub-Saharan Africa, the Middle East, South America, Papua New Guinea and central Australia.

In Australia, HTLV-1 is of greatest concern for Aboriginal and Torres Strait Islander people. In some remote Aboriginal communities, almost half the population carries the virus while in others, very few people do.

How does someone get HTLV-1?

HTLV-1 can be acquired from an infected person by: 

• blood transfusion or organ transplantation
• sharing needles
• sexual contact
• breastfeeding

You can’t catch HTLV-1 from hugging or kissing, or from sharing a glass. 

Problems caused by HTLV-1

If you are infected with HTLV-1, the virus won’t necessarily affect your health. Most people with HTLV-1 find it causes them no problems at all. 

But around 1 in 20 people develop one of two serious conditions: 

• adult T-cell leukaemia/lymphoma
• HTLV-1 associated myelopathy (also known as tropical spastic paraparesis or HAM/TSP). This is a chronic disease of the nervous system that affects the spinal cord. It many affects people who are over 40.

HTLV-1 infection can also cause other conditions such as a lung disease called bronchiectasis and conditions that affect the skin, eyes and thyroid gland. 

Adult T-cell leukaemia/lymphoma

Adult T-cell leukaemia/lymphoma is a type of cancer caused by white blood cells multiplying abnormally quickly. It can affect the blood (leukaemia) or the lymph nodes (lymphoma).

Adult T-cell leukaemia/lymphoma develops: 

• in 1 in 20 people who are infected with HTLV-1
• mostly in people who became infected as a baby
• usually decades after the infection is acquired

Some types of adult T-cell leukaemia/lymphoma develop very quickly while others develop much more slowly. 

Symptoms typically include: 

• swollen lymph nodes
• fatigue
• skin rash
• nausea and vomiting
• fevers and sweats

HTLV-1 associated myelopathy/tropical spastic paraparesis

About 1 in 25 people with HTLV-1 infection will develop HAM/TSP.

Symptoms include:

• progressive muscle weakness in the legs
• muscle stiffness and spasms
• lower back pain
• inability to control their bladder or bowels

HTLV-1 diagnosis

HTLV-1 infection is usually diagnosed using a blood test to detect antibodies to the virus. 

Because many people have no symptoms, some will only learn that they are carrying the virus when blood is being tested for other reasons. Australian blood donor centres have been screening blood for HTLV-1 infection for 25 years. 

HTLV-1 treatment

HTLV-1 infection is a lifelong condition. There is no specific treatment if you have the virus, and you are well. 

If you are unwell, however treatment is available and you should talk to your doctor:

• If you have adult T-cell leukaemia/lymphoma, there are many treatment options including antiviral drugs, chemotherapy and stem cells transplants. 
• If you have HAM/TSP, there are plenty of ways to control and relieve specific symptoms. 

HTLV-1 prevention

You can reduce the risk of passing on or getting the HTLV-1 virus by:

• following safe sex practices such as using a condom
• not sharing needles

If you have the virus, you can reduce the chance of passing the virus to your baby by avoiding breastfeeding, or by breastfeeding for no more than 6 months. Talk to your midwife, nurse or doctor.

More information

• Leukaemia Foundation