Doctors from around the world are urging the World Health Organization to pay closer attention to a deadly virus that has been dubbed “the cousin of HIV,” but one that has been mostly ignored.

It’s called HTLV-1, or human T-cell leukemia virus type 1, and though it was discovered nearly 40 years ago, most Canadians have likely never heard of it.

That’s because the virus is still relatively rare in Canada. But in Australia, it’s spreading at "astounding" rates, according to the Global Virus Network, a coalition of the world’s foremost virologists.

The group’s members worry that the virus will spread more widely if more isn’t done, and are calling on the WHO to take action.

Dr. Isaac Bogoch, an infectious diseases specialist at Toronto General Hospital, said the medical community still understands very little about this cancer-causing virus.

“The reason we don’t know a lot about this virus is because the vast majority of those with this virus have no symptoms whatsoever,” Dr. Bogoch explained to CTV’s Your Morning Tuesday.

Only about 5 per cent of those infected develop symptoms – or more accurately, complications of the virus. Those complications include certain types of cancers. In fact, the GVN calls HTLV-1 “one of the most potent human carcinogens," responsible for a rare blood-based form of lymphoma called adult T-cell leukemia/lymphoma.

It also leads to paralyzing neurologic disorders and suppresses the immune system, leaving carriers open to potentially fatal infections.

Recent research has shown the virus is spreading, particularly among Indigenous people of Australia, where as many as 40 per cent of men have tested positive.

Currently, the highest known prevalence is in Japan. But there are also clusters of infection in several islands of the Caribbean, Brazil, Peru, and central Africa. In all, between 10 to 20 million people worldwide may be infected.

“No one is entirely sure why this virus has specific pockets all over the world,” Dr. Bogoch said.

Because there is no cure and no vaccine against HTLV-1, the virologists are calling on the WHO to step in to promote ways to stop its spread.

Like HIV, HTLV-1 originated from non-human primates and spreads in much the same way: through infected blood and bodily fluids. The virus can be transmitted through shared needles, through breastfeeding, and through sexual activity.

The risk of transmission can be reduced in much the same ways as HIV as well: by not sharing needles, by using barriers during sex, and by screening blood and organ donations for the virus.

Dr. Bogoch said there are excellent tests to spot the virus; what’s needed is simply more testing. So far, Japan is the only country that has a national screening program for HTLV-1 (it’s also the only country working on a vaccine), and Dr. Bogoch said that needs to change.

“It’s really important to know who has the virus and who doesn’t, because if people do have the virus, they can be counselled about the potential complications. So if there are issues, they can seek medical attention early,” he said.

“In addition, if we know who has the virus, we can also counsel on how to prevent them from transmitting it to others.”