Scientists taking up arms in the fight against silent killer HTLV-1

On 10 November, a team of international scientists will organise World HTLV Day, giving attention to a deadly virus no one’s heard of. HTLV-1 hacks our genetic code and silently spreads amongst communities. It’s estimated that worldwide twenty million people are infected.

First discovered in 1978, the HTLV-1 virus has already claimed millions of lives. At that point, it had already been around for thousands of years, yet today no one’s heard about it. This silent killer can stay dormant for decades before symptoms occur - if they ever do. But once someone carries the virus, they can infect others through sexual contact, needles, organ transplantation, blood transfusions or breastfeeding, allowing the infection to spread like wildfire. Researchers are now speaking up about this poorly-known disease, fighting to get resources for the estimated 20 million people infected worldwide. One of those researchers is Johan Van Weyenbergh, a scientist at the Laboratory for Clinical and Evolutionary Virology (Rega-Instituut, KU Leuven). 

HTLV-1: what’s that?

HTLV-1 is a retrovirus: a type of RNA virus that essentially hacks our genetic code by inserting a copy of its genome into the host cell, which is then reverse-transcribed into our DNA. If this sounds familiar, it’s because there’s another retrovirus that uses the same mechanics: HIV. 

HTLV-1 was actually the first retrovirus to be identified, paving the road for HIV research. But shortly after its discovery in 1978, the HTLV-1 virus sank back into obscurity when the battle turned to the HIV-virus.

Though the disease is barely known, the infection rates are startling. In Central Australia, up to 45% of the indigenous population is infected, and 7% of the entire population in Gabon carries the virus. The infection rate is also very high in Peru, the Caribbean, Brazil, Romania, and other countries. "But what we’re seeing is likely the tip of the iceberg," says Johan Van Weyenbergh, "We simply don’t have any data on the infection rate in China, India, or most countries in Europe, including Belgium. That means we don’t have information on the infection rates in half of the world’s population. This lack of data and information could prove fatal: earlier this year, three leukaemia patients were accidentally discovered in Brussels. By the time they were diagnosed with the virus, it was too late: all of them died soon after." 

We simply don’t have any data on the infection rate in China, India, or most countries in Europe, including Belgium. That means we don’t have information on the infection rates in half of the world’s population.

While most people who contract the virus remain asymptomatic, about 1 in 20 patients develop severe symptoms. In adults, the disease usually manifests itself through either an aggressive and deadly form of T-cell leukaemia or through progressive paralysis of the lower body, causing mobility issues, incontinence, and sexual dysfunction. Children usually display infective dermatitis, which causes large, unsightly lesions on the patient’s skin. 

A disease of women and the poor 

"At the moment, there’s no cure and no way to halt the progression of the illness," Van Weyenbergh says, "because we lack the data and we lack the funding. The virus often manifests itself in poorer regions, where people often struggle to survive. They don’t have the luxury to worry about a disease which often manifests later in life. The virus mostly affects women, who often become infected through unsafe sex and may infect their babies through breastfeeding. And if the virus gives its victims infective dermatitis or paralyzes them, they’re stigmatized, because their disease becomes very visible. Those people are ostracised, pushed even further into poverty. It creates an environment in which the virus will continue to thrive due to a lack of public awareness and testing. We need to speak up. We need to take action."


HTLV is short for ’human T-lymphotropic virus’ and comprises four different viruses: HTLV-1, HTLV-2, HTLV-3, and HTLV-4. When HIV was first discovered, it was thought to be a variety of HTLV, and it was called HTLV-3. Later, it was renamed to HIV, and the virus now known as HTLV-3 has nothing to do with AIDS anymore. Recently, due to the strong link it has with cancer, HTLV-1 was renamed ’Human T-cell Leukaemia Virus’. 

HIV became well-known as people spoke up about it, and an army of scientists studied the virus, developed medications, and prevention campaigns were set up. However, this increased awareness came with the unfortunate side effect that patients became stigmatized. "I’ve known people to avoid taking their medications at work or around other people in general because they’re scared others will find out. They’re afraid of losing their job, losing the income they need to buy medicine, losing their friends," Van Weyenbergh says, "this huge stigma exists around HIV, and it’s spread to those who suffer from HTLV-1. Once you tell a patient they’re infected with a retrovirus, they’ll immediately think they’ve contracted HIV, because that’s simply the most well-known retrovirus. HTLV-1 is still not completely understood, and doctors often refer to those infected as ’carriers’ or ’seropositives’, which is scientifically correct but has enormous consequences for the patient’s personal life. There’s so much fear." 

Japan: a success story

In Japan, an estimated 0.8 million people are HTLV-1 positive and, in Southern regions of Japan, 30-40% of adults below the age of 50 and up to 5.8% of pregnant women carry this virus. But where we are largely unaware of the disease, the Japanese are not. "Since the discovery of HTLV-1, Japanese campaigns focusing on sexual health have been set up, successfully reducing the number of infections," explains Van Weyenbergh. "Japan has also started giving out formula milk to mothers who’d otherwise be breastfeeding. The country has invested a lot of money in research and prevention, with great success. We have much to learn from their approach." 
In 1987, measures taken in the Nagasaki region reduced the number of infected mothers from 7.2% to 1%. When Japan started screening all expecting mothers, transmission from mother to child was reduced from 20% to 2.5%. But Japan’s approach is the exception to the rule: worldwide, HTLV-1 remains largely unchallenged. 

In Japan, an estimated 0.8 million people are HTLV-1 positive and, in Southern regions of Japan, 30-40% of adults below the age of 50 and up to 5.8% of pregnant women carry this virus.

The situation in Belgium 

"In Belgium, the situation is pretty straightforward: we’ve got little to no idea about the infection rate amongst the population, not even in risk groups. And though it’s probably quite low, we need to take action if we want to eradicate this disease. Those three leukaemia patients who died in Brussels earlier in 2018 were diagnosed purely by accident and way too late," Van Weyenbergh explains. 
"We need to acknowledge that HTLV-1 is a problem, we need to gather resources and, most of all, we need to invest in the people at risk and those infected," Van Weyenbergh emphasizes. "The Netherlands are already taking steps in the right direction: they’re now retroactively figuring out how many cases of leukaemia might have been caused by HTLV-1. Belgium needs to follow suit. Scientists already wrote an open letter to the WHO, signed by sixty people, in which they address the current lack of knowledge, the lack of attention for the patients and the lack of prevention measures." 
For example, infection through blood transfusions or transplants is a risk and donated blood and tissues aren’t routinely checked for HTLV-1 yet because the tests are expensive.

An open letter to the WHO (excerpt) 

HTLV-1 was discovered 37 years ago (40), just before the AIDS epidemic. It is acknowledged that HTLV-1 research led to the idea that AIDS might be caused by a new retrovirus and therefore greatly abetted the identification of HIV-1. It is disappointing that despite the significance of HTLV-1 research in the fight against AIDS, in comparison to HIV-1, people who are infected with HTLV-1 have received very little attention in form of publicity, development of international clinical guidelines or financial investment into drug development and clinical trials (41).
Worldwide it is mostly women, who carry the burden of HTLV-1 infection and its associated diseases: Women, who become infected through condom-less sex, and their babies, who are infected through breastfeeding. Therefore HTLV-1 is highly concentrated in families [1:3 to 1:4 of family members carry the virus (42, 43)].

In your speech on 3 July 
2017 you fearlessly stated that the WHO is fully committed to ’Every Woman Every Child’. You asked for quality, equity and dignity in services for sexual and reproductive health, equal rights and the empowerment of women, girls and communities. Today we are asking you to include families at risk of HTLV-1 in your list of goals to improve global health.

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World HTLV Day

To create more visibility and awareness, a group of international researchers decided to make 10 November ’World HTLV Day’. In Tokyo, Kagoshima, Rio de Janeiro, Salvador-Bahia, São Paulo and other big cities around the world, people will be hitting the streets to make their voices heard. They’ll illuminate bridges and monuments to get attention for those who suffer from HTLV. In Leuven, the KU Leuven University Library will be illuminated for this purpose. In Rio de Janeiro,  the statue of Christ The Redeemer will be lit up in red and white: the colours of the HTLV campaign. 

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