HTLV (Human T-cell Lymphotropic Virus)

Most people with HTLV do not develop any symptoms. Around 90–95% of people with HTLV-1 remain healthy and may never know they have the virus unless they are tested.

A small proportion of people with HTLV-1 may develop associated conditions, sometimes many years after infection. Symptoms can include:

• Weakness or stiffness in the legs
• Difficulty walking or frequent falls
• Bladder or bowel problems
• Swollen lymph nodes
• Persistent skin rashes
• Fever, fatigue, or unexplained weight loss

These symptoms can have many possible causes and do not necessarily mean you have HTLV. If you have persistent symptoms or are concerned about your risk, a blood test can confirm whether you have the virus.

Yes. Most people with HTLV never develop noticeable symptoms and may not realise they have the virus unless they are tested.

Although most people with HTLV-1 remain healthy, a small proportion may develop HTLV-1-associated illnesses later in life. If you think you may have been exposed, a blood test is the only way to confirm your HTLV status.

Most people with HTLV never develop complications. However, a small proportion of people with HTLV-1 may develop associated health conditions, sometimes many years after infection.

These include:

• HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a condition affecting the spinal cord that can cause weakness, stiffness, and difficulty walking
• Adult T-cell leukaemia/lymphoma (ATL), a rare type of blood cancer
• HTLV-1-associated uveitis, an inflammatory condition affecting the eyes
• Infective dermatitis, a chronic skin condition associated with HTLV-1

There is currently no treatment that can eradicate HTLV-1 infection in people who are otherwise well. However, regular monitoring can help identify complications early and ensure appropriate treatment if they occur.

Most people with HTLV never develop symptoms. For those who do, symptoms may appear many years after the initial infection.

Conditions such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukaemia/lymphoma (ATL) are associated principally with HTLV-1. These conditions can develop after a prolonged symptom-free period, although the time between infection and the development of disease can vary.

Because HTLV often causes no early symptoms, testing is the only way to know if you have the virus.

HTLV is caused by the Human T-cell Lymphotropic Virus, which infects a type of white blood cell called T-cells. There are two main types, HTLV-1 and HTLV-2, with HTLV-1 being the type most commonly associated with disease.

HTLV can be passed through:

• Sexual contact without a condom
• Sharing needles or other injecting equipment
• From mother to baby, mainly through breastfeeding
• Blood transfusions or organ transplants in countries where screening is not routinely performed

HTLV is not spread through casual contact such as hugging, kissing, or sharing food, drinks, or household items.

You may be at higher risk of HTLV if you:

• Have unprotected sex with an infected partner
• Share needles or injecting equipment
• Were breastfed by someone with HTLV
• Being born in, having lived in, or having sexual partners from regions where HTLV-1 is more common, including parts of the Caribbean, sub-Saharan Africa, south-west Japan, and South America
• Received a blood transfusion or organ transplant in a country where HTLV screening is not routinely performed

If you think you may have been exposed, a blood test can confirm whether you have HTLV.

You can reduce your risk of HTLV by avoiding contact with infected blood and practising safer sex.

This includes:

• Have unprotected sex with an infected partner
• Never sharing needles or other injecting equipment
• Discussing testing if you or your partner may be at risk
• If you have HTLV and are pregnant, seek specialist advice about infant feeding, as breastfeeding can transmit HTLV-1

In the UK, donated blood and organs are routinely screened for HTLV, making transmission through medical procedures extremely rare.

Yes, although the risk is much lower. Condoms significantly reduce the risk of HTLV transmission during vaginal and anal sex but do not provide complete protection.

HTLV can also be transmitted through sharing needles or from mother to baby through breastfeeding. If you think you may have been exposed, a blood test is the only way to confirm your status.

No. HTLV is not spread through kissing or saliva.

It is also not transmitted through hugging, shaking hands, sharing food or drinks, or other everyday social contact. HTLV is spread through infected blood, unprotected sex, and from mother to baby, mainly through breastfeeding.

No. HTLV is not spread by sharing towels, clothing, cutlery, toilet seats, or other household items.

The virus is transmitted through infected blood, unprotected sexual contact, and from mother to baby through breastfeeding. Everyday contact does not pose a risk.

Yes, but the risk depends on where the transfusion took place.

In the UK, donated blood is routinely screened for HTLV, making transmission through blood transfusion extremely rare.

HTLV is diagnosed with a blood test that initially detects antibodies to HTLV-1 and HTLV-2.

If the screening test is reactive, additional confirmatory testing is performed to confirm the result and determine whether the infection is HTLV-1 or HTLV-2. In selected cases, a PCR test may be used to detect HTLV proviral DNA, particularly for confirmation or differentiation when antibody results are unclear.

The main test for HTLV is a blood test that detects antibodies produced in response to HTLV-1 or HTLV-2.

If the result is reactive, additional tests are used to confirm the infection and identify whether it is HTLV-1 or HTLV-2. In certain situations, PCR may be used to detect HTLV proviral DNA, particularly when antibody results are unclear.

An accurate diagnosis is based on blood test results alongside your medical history.

Your clinician may ask about:

• Possible exposure through sex, blood, or breastfeeding
• Whether you were born in, have lived in, or have relevant exposure to people from regions where HTLV is more common
• Any symptoms that could be associated with HTLV

A reactive screening test should always be confirmed with additional laboratory testing before a diagnosis is made.

HTLV-associated conditions can resemble other diseases and may cause symptoms that overlap with other conditions.

For example, neurological symptoms associated with HTLV-1 may resemble multiple sclerosis or other disorders affecting the spinal cord, while blood-related complications such as adult T-cell leukaemia/lymphoma (ATL) may resemble other types of leukaemia or lymphoma.

Because most people with HTLV have no symptoms, blood testing is needed to confirm an HTLV infection.

The standard way to diagnose HTLV is with a blood test that detects antibodies to HTLV-1 or HTLV-2.

In some situations, PCR may be used to detect HTLV proviral DNA, particularly when antibody results are indeterminate or when testing infants. Cerebrospinal fluid (CSF) testing may be undertaken as part of a specialist investigation when HTLV-associated neurological disease, such as HAM/TSP, is suspected. It is not a routine alternative test for diagnosing HTLV infection.

No. A physical examination cannot diagnose HTLV.

Most people with HTLV have no visible symptoms. Diagnosis requires a blood test to detect antibodies to the virus or, in some cases, HTLV proviral DNA.

No. HTLV cannot be diagnosed by symptoms alone or with most standard home STI tests.

Diagnosis requires a laboratory blood test. Because HTLV is not routinely included in standard STI screening, you may need to request a specific HTLV test if you think you have been exposed.

If testing is performed soon after a possible exposure, repeat testing may be recommended because antibodies may not yet be detectable. The timing of repeat testing should be guided by the laboratory or a healthcare professional.

The long-term outlook is good for most people with HTLV-1, and most remain asymptomatic throughout their lives.

A small proportion of people with HTLV-1 may develop associated conditions, such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) or adult T-cell leukaemia/lymphoma (ATL), sometimes many years after infection. Appropriate clinical follow-up can help identify and manage these conditions if they occur.

There is currently no treatment that eliminates HTLV infection. Once infected, the virus usually remains in the body for life.

Treatment is directed at associated conditions if they develop. If you have HTLV, your healthcare professional can advise you about appropriate monitoring and ways to reduce the risk of passing the virus to others.

HTLV does not “come back” because the infection usually remains in the body for life.

Most people with HTLV never develop symptoms. Appropriate clinical assessment and follow-up may be recommended, particularly for people with HTLV-1.

You can also reduce the risk of transmission by practising safer sex, not sharing needles or injecting equipment, and not donating blood or breast milk.

Yes. If you have HTLV, you should tell your current sexual partner because the virus can be transmitted through sexual contact.

Your current sexual partner should be advised to discuss HTLV testing with a healthcare professional. Testing of previous sexual partners may also be appropriate depending on the exposure history.

If you need support with partner notification, sexual health services can discuss your options and help you inform partners confidentially where appropriate.

Yes. If you have HTLV, you can reduce the risk of transmission by:

• Using condoms during vaginal and anal sex
• Not sharing needles or injecting equipment
• Not donating blood, semen, or breast milk
• Following specialist advice regarding organ donation
• Seeking specialist advice about infant feeding if you have HTLV, as HTLV-1 can be transmitted through breast milk
• Encouraging current or previous sexual partners to discuss testing with a healthcare professional, where appropriate

These measures can help reduce the risk of passing HTLV to others. There is currently no vaccine to prevent HTLV infection.

Yes. HTLV-1 can be passed from mother to baby during pregnancy, around the time of birth, or through breastfeeding. However, breastfeeding is the main route of mother-to-child transmission, while transmission during pregnancy or around delivery is much less common.

If you have HTLV-1 and are pregnant or planning a pregnancy, your healthcare team can advise you on ways to reduce the risk of passing the virus to your baby.

HTLV-1 infection is not generally associated with major adverse effects on the course of pregnancy itself. The principal concern is mother-to-child transmission, particularly through breastfeeding.

If you have HTLV-1, your maternity team can discuss feeding options and any additional care you or your baby may need.

HTLV is uncommon in the UK, and universal antenatal HTLV screening is not currently part of routine pregnancy screening.

Testing may be recommended if you have risk factors, such as being born in or having lived in an area where HTLV is more common, having a mother or sexual partner with HTLV, or having another relevant exposure history.

If you are concerned about your risk, speak to your healthcare professional about whether an HTLV blood test is appropriate.

There is currently no established antiviral treatment during pregnancy that eliminates HTLV-1 or is routinely recommended to prevent transmission from mother to baby.

Management focuses primarily on appropriate counselling and reducing the risk of postnatal transmission, particularly through breastfeeding.

Yes. If you have HTLV-1, you should discuss your diagnosis with your maternity team early in your pregnancy.

They can advise you on ways to reduce the risk of transmission, including:

• Discussing infant-feeding options, as HTLV-1 can be transmitted through breast milk
• Attending recommended antenatal appointments
• Following advice from your obstetrician or specialist team

Avoiding breastfeeding can substantially reduce the risk of mother-to-child transmission.

HTLV does not usually affect postpartum recovery.

However, HTLV-1 can be transmitted through breast milk, so people with HTLV-1 should receive specialist advice about infant feeding. Avoiding breastfeeding can substantially reduce the risk of passing HTLV-1 to the baby.