A very old viral infection in humans is becoming a substantial threat. It is devastating people in central Australia, among other locations. Could it be the second coming of HIV…and headed for the US and everywhere else, too? For answers, we turned to Robert C. Gallo, MD, the scientist who with his colleagues reported the discovery of this virus, HTLV-1, in 1980, but whose attention turned to HIV/AIDS when that virus swept across the globe.


Most people have never heard of HTLV-1, and it was even off the radar of many health professionals until quite recently. But researchers renewed the alarm about HTLV-1—that stands for “human T-cell leukemia virus Type 1”—at the 2017 international meeting of Dr. Gallo’s Global Virus Network in Melbourne, Australia. HTLV-1 had already been identified as the first human virus known to directly cause a human cancer, specifically an adult T-cell leukemia and lymphoma, and the first human retrovirus ever shown to cause disease at all. Later a French group showed that it also causes a severe paralytic neurological disease. But now, it’s also been found to cause a deadly lung infection, called bronchiectasis, and it is killing one particular group of people in far less time than the decades it takes for those cancers to develop, Dr. Gallo said.

HTLV-1 is a retrovirus. It’s not as immediately infectious as most other viruses, such as the flu virus, but rather it takes some time to find a way into the DNA of people exposed to it. An astonishing 45% of the indigenous people in Alice Springs, Australia, are infected with HTLV-1. And that’s not the only place. Other pockets of rampant HTLV-1 infection around the world are in New Guinea, Japan, Haiti, Jamaica, Peru, Chile, Brazil, Colombia, West Africa and Florida, primarily involving immigrants from the Caribbean region. There is an important difference between the outbreaks in Australia and elsewhere, according to Yutaka Tagaya, MD, PhD, a colleague of Dr. Gallo’s. The virus currently affecting Alice Springs is a different subtype than the one seen in the other hot spots and may be more infectious—the lung infection is killing more people and doing so much faster than any other illness caused by HTLV-1. But the how and why of the rampant lung infection are still mysteries.

Important note: According to a study on HTLV-1–infected patients in Florida published in Blood Advances, the leukemia/lymphoma caused by the disease is very aggressive and ultimately fatal. There are currently trials of antiviral drugs under way and anti-CCR4 antibody therapy is approved in Japan to combat the disease.


Other than a few news headlines that followed the Global Virus Network meeting, we haven’t heard much about HTLV-1 in the US because it is still relatively rare here—less than 0.1% of Americans overall are infected. But it is disproportionately hitting certain groups—while very few Americans of European descent have been infected, 1% to 2% of African Americans have been infected, a comparatively huge number.

Being infected does not mean a particular person will necessarily develop cancer or another illness—some people are just carriers. But because HTLV-1 is similar in important ways to its cousin HIV, it’s important to be aware of it. Like HIV, HTLV-1 is a sexually transmitted disease and can be spread through exposure to infected blood and from mother to child through breastfeeding.

The US, Australia, Japan, Peru, Brazil and most European countries test their blood banks for the virus, but not all countries do. Medical centers in the US used to, but no longer do, test transplant organs for HTLV-1, the government’s rationale being that there are too few cases of HTLV-1 to justify the cost, especially in view of a high rate of false positives from the test. Dr. Gallo points out that the risk may need to be reevaluated in light of recent studies in Japan in which the HTLV-1 infection associated with organ transplants was shown to substantially increase the chances of developing aggressive neurological disease.

As one of the scientists who first connected the dots between HIV and AIDS, Dr. Gallo is advocating for HTLV-1 to be added to the list of sexually transmitted diseases maintained by the World Health Organization, which recognizes it but has not given it the importance of other diseases. Greater recognition by the WHO would almost certainly speed up efforts around the world for development of treatments and a vaccine and for additional countries to test their blood supplies and transplant organs. Dr. Gallo believes that if all focus hadn’t completely shifted to HIV when it was discovered, science could have prevented what’s happening now to the indigenous people of central Australia.

Until this all happens, he suggests the following to protect yourself from being infected by HTLV-1, particularly if you’re a world traveler…

  • Practice safe sex, get tested and ask any partners to be tested for the virus, as many people do for the HIV virus.
  • Be aware of the blood-testing practices of the country you’re in, and if there’s any way to avoid it, don’t get a blood transfusion in a country that does not test its blood supply for HTLV-1.
  • If you need an organ transplant, ask that the organ be tested for HTLV-1.

Note: If you’re pregnant, get tested for HTLV-1 and, if you test positive, don’t breastfeed.

Could HTLV-1 take us by surprise and become a ubiquitous killer the way HIV did in the 1980s? Both Dr. Gallo and Dr. Tagaya think that type of global epidemic is unlikely because HTLV-1 is not nearly as easily transmitted as HIV. It’s an older virus, and mankind has already somewhat adapted to it biologically. But more and more people are being exposed to it. For instance, HTLV-1 hotspots in Japan used to be only in the southwest and northern parts of the country, but now there is one in Tokyo as well. Both Drs. Gallo and Tagaya said that we’re probably seeing the early stages of what will become a global problem, but not with the speed or prevalence of HIV.