An infectious disease expert explains the situation with HTLV-1, a virus for which there is no vaccine or drug cure: ‘It’s a silent pandemic because 90% of people have no symptoms’

Vicente Soriano is Vice Dean for Research at the School of Health at the International University of La Rioja (UNIR) and an infectious disease specialist. The doctor was the moderator of an event organized by the Institute of Physicians and Surgeons of Madrid (ICOMEM) on September 15 around the HTLV-1 virus, which has been called the protagonist of a “silent epidemic” because it is barely tracked and not searched for. Although the symptoms can be very serious.

Is a strange disease It has spread very little in Europe, but with the globalization of the 21st century, small incidents have occurred domestically. Spain is one of the few countries in the world with a national case count, which has barely reached 500 since 1989, the year surveillance began. However, the scientific community actually believes that there are many more cases that have gone undetected because asymptomatic infections account for 90% and therefore they are simply carriers of the virus.

Q: What are the characteristics of this virus?

Answer: There are two types of viruses, one is a virus containing DNA, and the other is a genetic material containing RNA. RNA has been the protagonist of epidemics of the past fifty years: HIV, hepatitis C, Ebola or SARS (coronavirus). HIV emerged in 1981, but HTLV-1 had been described two years earlier, hence its name. AIDS is HTLV-3. The media influence is all about HIV, but the virus has been around in humans for much longer.

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Q: What symptoms does HTLV-1 cause?

It produces two diseases: T-leukemia, which is the rarest and has a poor prognosis since most people diagnosed die; and myelopathy, which presents with loss of strength in the lower limbs. HTLV-1 has previously appeared in the tropics, sub-Saharan Africa, and Latin America. There, it’s called tropical spastic paraplegia.

Like HIV, it is passed from mother to child through sex, blood transfusions, or during breastfeeding. In Europe we have no cases, but with migration movements in the 21st century some cases have emerged. In Spain we diagnose about 20 cases every year, but we call it a silent pandemic because many cases go undiagnosed because 90% are asymptomatic. Unlike the HIV virus, one develops into AIDS ten years later rather than living with the disease. Only 10% of those infected develop symptoms, either blood cancer or paralysis. The other 90% died from the virus, but not from the virus. They are carriers. Because they don’t know they are infected, they can spread it to others.

Q: Can it be detected? What’s wrong?

It can be detected, but one of the conclusions we came to was that it would be recommended to include it in anti-production tests or sexually transmitted screening tests that don’t currently exist. It doesn’t exist because no one realizes it’s a sexually transmitted virus. We are at the stage where doctors and public administrations realize that the costs of controlling it are very low.

But another big problem is that there is no vaccine or medicine. We already have solutions for HIV and hepatitis, but the only prevention mechanism is to avoid exposure. Those with leukemia are often given monoclonal antibodies, but their prognosis is so poor that we try bone marrow transplants, which is a dangerous intervention. For prevention via the sexual or maternal-fetal route, HIV anti-fat inhibitors such as Cabotegravir have been used experimentally but with limited efficacy due to a lack of clinical trials.

Q: Is the mortality rate of this disease high?

Answer: The mortality rate of T leukemia exceeds 80% after three years. Myelopathy does not cause death, but people with myelopathy can end up in wheelchairs and develop autoimmune diseases. Spain is one of the only countries to have a national case registry since 1989. Other countries do, but do not have national registries. Since then we have accumulated nearly 500 cases.

Q: Are the confirmed cases due to symptoms?

A: A large proportion of the cases registered were because they had symptoms, but when we screened family members we found that some other people were also infected. Also in blood banks, because in Madrid, Catalonia and other communities, they do look for HTLV-1 for blood donations and the diagnosis is found there.