HIV's Largely Ignored Relative, HTLV-1, Has Prevalence Rates of Up to 40% in Some Remote Areas

May 10, 2018


Credit: PD-UsGov [Public domain] via Wikimedia Commons

Human T-cell leukemia virus type-1 (HTLV-1) was the first retrovirus discovered in humans. In the almost four decades since that finding, it has not spread nearly as far nor gotten nearly as much attention as its viral cousin, HIV, but prevalence is extraordinarily high in certain remote communities around the globe. Now, doctors are warning that we are not doing enough to understand and stop the virus.

A study wrapping up next month at Alice Springs Hospital in Central Australia has found that rates of infection in one local community are over 40% among adults. As CNN reported earlier this week, one of the researchers who discovered the virus thinks this should be a wake-up call to public health that we need to do more.

Robert Gallo, M.D., and his colleagues at the National Institutes of Health discovered HTLV-1 in 1979 (a similar discovery made around the same time by researchers in Japan was later found to be the same virus), but researchers believe it is far older than that: The virus's DNA has been found in 1,500- year-old mummies. The discovery was a scientific breakthrough that was vital to the identification of HIV just a few years later because it was the first time a retrovirus had been isolated in humans. In fact, until then, it was believed that retroviruses couldn't infect humans.


Like HIV, the HTLV-1 virus attacks T-cells leading to a weakened immune system. HTLV-1 can cause leukemia and lymphoma (cancers of the blood and lymphatic system), debilitating neurological issues, eye disease, and problems with bones and joints. It also causes bronchiectasis, a condition that damages the lungs, which is currently responsible for deaths in the impacted region of Australia.

Again like HIV, HTLV-1 is spread through infected bodily fluids such as blood, semen, vaginal secretions, and breast milk. Blood-to-blood transmission, such as during an infusion, is the most risky, but HTLV-1 can also be sexually transmitted or passed from mother to child. Though far less is known about HTLV than HIV, Gallo is confident that this virus does not spread through casual contact. He told CNN: "In short, I would not be afraid to use towels, drink out of the same glass, be part of the family, et cetera [as a person with HTLV-1]."

It is estimated that 20 million people are infected with HTLV-1 worldwide. Prevalence remains low in many countries, including the U.S. and the United Kingdom. Pockets, however, are scattered across the globe in which rates are alarmingly high. In addition to Australia, Brazil, Colombia, French Guyana, Gabon, Iran, Japan, Melanesia, Peru, and Romania, among others, have isolated areas of high prevalence. Communities affected by this virus share common characteristics; They tend to be poor, remote, and have few health resources available. The area in Australia that is currently battling HTLV-1 is populated by indigenous people.

That we know less about this virus than about HIV makes sense because HTLV-1 appears to be less efficient at transmission. The risk of mother-to-child transmission of HTLV-1, for example, is estimated to be 20% compared with 25% to 40% risk for pregnant women with HIV who are not receiving any drug therapy. Moreover, researchers have estimated that up to 90% of those who contract HTLV-1 will remain asymptomatic carriers throughout their lifetime, meaning they will likely not know they have acquired it and won't become ill but can transmit the virus to others.

The lack of public health activity around HLTV-1 is a problem for areas in which the virus is endemic and could lead to further global spread. There is, for example, no universal screening program for donated blood or tissues (though most developed countries do screen the blood supply). Graham Taylor, M.B., Ch.B., D.Sc., who runs the HTLV service for the United Kingdom, told CNN that this is one of worrisome the public health issues caused by the lack of response to the virus: "Then, you have the situation where blood which is infected with HTLV-1 can be given to a recipient, an organ can be given to a recipient." In addition, Japan is the only country that has a national screening program for pregnant women. Such programs are important because they can encourage women who have the virus to use formula, as most mother-to-child transmission happens during breastfeeding.

The lack of in-depth knowledge of the virus is also a problem, according to those who work in the field. In the CNN article, Gallo pointed out that no one understands why the prevalence of this relatively inefficient virus is so high in certain areas. He said it was possible that the areas have a variant of HTLV-1 that transmits more easily, but no one has done the research to confirm this hypothesis.

At this point, experts are not concerned about rapid spread of the HTLV-1 worldwide, but they do believe science needs to pay more attention to this neglected virus. Gallo, who is co-founder and director of the Institute of Human Virology at the University of Maryland School of Medicine, told CNN: "We have to get attention to HTLV-1 quick." He pointed out that as of now nobody has done anything to treat or prevent the disease and calls the field "wide open for vaccine research."

It is understandable that the world took its collective eye off the first retrovirus discovered in humans once its more-efficient, more-deadly cousin demanded attention, but now we have to make up for lost time.

Martha Kempner is a freelance writer, consultant and sexual health expert.

This article was provided by TheBodyPRO.

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