HTLV-1 and HTLV-2

Human T-lymphotropic Virus Type I and II

Human T-lymphotropic Virus (HTLV) is a virus that may cause blood or nerve disease. The AAP recommends that those who are HTLV I or HTLV II positive should not breastfeed or use expressed human milk as the primary route of HTLV-1 infection seems to be through human milk.1 2 3

Due to inadequate treatment options and the lack of effective vaccination, prevention is currently only possible by restricting transmission, including the usage of condoms during sexual intercourse or avoiding breastfeeding if HTLV-seropositive. If due to socio-economic reasons, breastfeeding cannot be avoided, short-term breastfeeding for a maximum of up to 6 months is suggested.4

Babies born to parents with HTLV-1 seem to acquire some limited immunity in-utero that may protect them in the early months but few studies have examined the impact of HTLV-1 infection on fertility or pregnancy outcomes or the susceptibility of the mother to infection during pregnancy and lactation. Breastfeeding is strongly associated with transmission and avoidance of breast-feeding a proven intervention, but little is known about the mechanism of transmission from the milk to the infant and there have been no clinical trials of antiretroviral therapy (ARV) to prevent this route of transmission.5

HTLV is not common in the US but is regularly found in some parts of Japan, the Caribbean, and Central Africa.6 Any concern about HTLV should be discussed with a qualified healthcare professional. Receiving a positive result from the initial blood test does not confirm positive HTLV status. Further testing will be necessary in order to rule out false-positive results.7

Most people with HTLV I or II do not develop the disease throughout life.8 9 We are of course not suggesting that an HTLV+ person donate their milk to someone else’s child. The below information can, however, be helpful in case the full health of a donor is not known:

  • HTLV-1 is destroyed within 20 minutes at 56°C (or 10 minutes at 90°C), or by freezing at -20°C for 12 hours.10
  • Freeze-thaw processing can eliminate the HTLV-I infectivity of human milk and HTLV-I carriers can indirectly feed their infants using expressed frozen-thawed milk as a way to prevent HTLV-I infection.11

Please see How can breastmilk be pasteurized at home? for more information on heat-treating and pathogens.

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  1. AAP. 2022. Breastfeeding and the Use of Human Milk ↩︎
  2. Renu B. Lal, et al. 1993. Evidence for Mother-to-Child Transmission of Human T Lymphotropic Virus Type II ↩︎
  3. Yoshiro Tsuji, MD, PhD. 1990. Prevention of Mother-to-Child Transmission of Human T-Lymphotropic Virus Type-Ipdf image ↩︎
  4. Ioannis Mylonas. 2010. HTLV infection and its implication in gynaecology and obstetrics ↩︎
  5. Carolina Rosadas and Graham P. Taylor. 2019. Mother-to-Child HTLV-1 Transmission: Unmet Research Needs ↩︎
  6. NORD – HTLV Type I and Type II ↩︎
  7. ARUP Laboratories – Human T-Lymphotropic Virus Types I and II Testingpdf image ↩︎
  8. NIH – Human T-cell leukemia virus type 1 ↩︎
  9. NIH – Human T-cell leukemia virus type 2 ↩︎
  10. Dr. John May, et al. 2005. La Trobe Tables ↩︎
  11. Yoshiya Ando, et al. 1989. Effect of Freeze-Thawing Breast Milk on Vertical HTLV-1 Transmission from Seropositive Mothers to Children ↩︎