HIV's Ancient Cousin, HTLV-1, Surging Through Indigenous Australian Communities

Human T-cell lymphotropic virus type I (HTLV-1) is the lesser-known cousin of human immunodeficiency virus (HIV), and while much less prevalent and virulent, health officials in Australia are concerned about a surge of cases in parts of the country’s Northern Territory.

Prior to the discovery of HIV, researchers discovered HTLV-1 — the first known human retrovirus – in 1979. The virus is blood-borne and is transmitted similarly to HIV, via blood transfusions, sexual intercourse, sharing needles with infected individuals, and from an infected mother to her baby during birth or through breastfeeding. An estimated 20% to 50% of babies born to infected mothers will become carriers of HTLV-1. Most individuals with the virus are asymptomatic, though the condition can progress and lead to adult T-cell leukemia/lymphoma (ATLL) and myelopathy/tropical spastic paraparesis (HAM/TSP). Other health conditions which may be linked to HTLV-1 infection include pulmonary diseases, certain cancers, eye inflammation, infective dermatitis, crusted scabies, and chronic low-grade immunosuppression. There is currently no treatment for chronic HTLV-1 infection, no cure, and no vaccine to prevent the virus.

HTLV-1 is endemic to Japan, the Caribbean, and parts of Africa. The disease can also be found in Iran, Iraq, southern India, China, Seychelles, Papua New Guinea, and Australia. Recently, Australian health officials have been on alert, as HTLV-1 infection rates have risen sharply in parts of the country. According to Australia’s Northern Territory Government, the Aboriginal populations have seen outbreaks of the virus. Previously, rates of HTLV-1 prevalence in Central Australia have been as high as 14%, 4.7% in the Northern Territory, and 0.5% in Darwin. The virus is considered uncommon in non-Aboriginal Australians.

Now, a recent news report has highlighted how HTLV-1 has become all too prevalent in some of the country’s Aboriginal communities. The report has made international headlines after pointing out that in 5 communities around Alice Springs, more than 45% of adults are infected with the virus, a rate thousands of times higher than that of non-indigenous Australians.

“Indigenous Australian residents of central Australia have the highest HTLV-1 prevalence in the world, exceeding 50% for adults in some remote communities surveyed so far” said Lloyd Einsiedel, PhD, an infectious diseases physician with the Baker Heart and Diabetes Institute based at Alice Springs Hospital, in a statement to the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine. “HTLV-1 causes significant morbidity and mortality but is an entirely preventable condition. Despite high rates of infection and disease, no strategy has been implemented to prevent HTLV-1 transmission among indigenous Australians.”

A 2016 study led by Dr. Einsiedal points out that part of the problem is that mother-to-child transmission is believed to be the primary mode of HTLV-1 transmission in central Australia, though testing for the virus is not a routine part of antenatal screening there. In addition, serving indigenous communities is difficult due to historical mistrust. In March 2018, Australia’s Department of Health announced that a health science center in Alice Springs was receiving an investment of $6 million to address the specific health challenges faced by the area’s indigenous communities, noting that the first priority project would be to address the issue of HTLV-1 there.

Health experts have been quick to note that Japan reduced HTLV-1 transmission rates by 80% over 2 decades through a targeted public health campaign, and can serve as a model for Australia in tackling this urgent outbreak.

Feature Picture Source: CDC / Cynthia Goldsmith. Picture Description: This image revealed the presence of both human T-cell leukemia type-1 virus (HTLV-1), (also known as the human T lymphotropic virus type-1 virus), and the human immunodeficiency virus (HIV).