DurgicalDurgical
EN
Open the app

Microbiology · Other RNA viruses

Human T-lymphotropic virus type 1 !

  • Virus
  • Enveloped
  • For completeness

A retrovirus that infects T cells. Most carriers never fall ill, but it can cause leukaemia or a slow paralysis of the legs.

Updated 2026-11-01

Also called: HTLV-1, HTLV-I

At a glance

Shape
Spherical
Genome
Single-stranded, positive-sense RNA, diploid
Envelope
Enveloped
Family
Retroviridae, genus Deltaretrovirus
Size
About 100 nm

Morphology

  • Enveloped virus with reverse transcriptase and integrase, like HIV
  • Infects mainly CD4 T cells and spreads from cell to cell

Transmission

  • Prolonged breastfeeding (the main mother-to-child route)
  • Sexual contact
  • Transfusion of cellular blood products and organ transplant
  • Shared needles

Reservoir: Humans

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Virulence factors

  • The Tax protein switches on T-cell growth genes and can lead to malignant transformation
  • Clonal expansion of infected cells rather than mass production of free virions
  • Chronic spinal cord inflammation from infected lymphocytes and the immune response

Diseases it causes

  • HTLV-1-associated myelopathy / tropical spastic paraparesis
  • Adult T-cell leukaemia/lymphoma

Clinical picture

  • Most infected people stay symptom-free for life
  • Tropical spastic paraparesis: progressive leg weakness and stiffness, low back pain, neurogenic bladder and bowel
  • Adult T-cell leukaemia/lymphoma: lymph nodes, hepatosplenomegaly, skin lesions, hypercalcaemia
  • Others: uveitis, infective dermatitis, higher risk of severe strongyloidiasis

Diagnosis

  • Screening with an immunoassay (ELISA)
  • Confirmation with Western blot, line immunoassay or proviral DNA PCR, which separates HTLV-1 from HTLV-2
  • In myelopathy: CSF antibodies and spinal MRI
  • In leukaemia: "flower cells" on the blood film

Treatment

There is no effective antiviral treatment for the infection. Myelopathy is managed with corticosteroids and rehabilitation; leukaemia/lymphoma with chemotherapy, zidovudine with interferon in some subtypes, and monoclonal antibodies in specialized centres.

Drug class only; doses and regimens are set by the clinician from the current guideline.

Prevention

  • Screening of blood and organ donors
  • Avoiding or shortening breastfeeding by mothers with HTLV-1 when safe alternatives exist
  • Condoms and not sharing needles
  • No vaccine

Test yourself

Think of the answer, then tap the question to see it.

Which neurological disease does HTLV-1 cause?

HTLV-1-associated myelopathy or tropical spastic paraparesis, with progressive leg weakness and stiffness.

Which HTLV-1 protein is linked to malignant transformation of T cells?

The Tax protein, which switches on cell growth genes.

Which region of Colombia is a classic HTLV-1 focus?

The Pacific coast, especially Tumaco in Nariño.

Add to my cards (3)

← Back to the group: Other RNA viruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Human T-lymphotropic virus-1 (World Health Organization (WHO), 2025); Association between lymphocytotropic virus type I (HTLV-I) infection and Pacific spastic paraparesis (Colombia Médica (Universidad del Valle), 1986).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.