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Blood in bags and vials
Photo by Daniel Gay

A group of scientists and activists are calling on the World Health Organization (WHO) to fight the spread of human T-cell leukemia virus subtype 1 (HTLV-1).

The group has written a letter to the WHO highlighting the global prevalence of HTLV-1 infection and recommending strategies to prevent the transmission of HTLV-1.

An abbreviated version of the letter was published in The Lancet. The full letter is available on the Global Virus Network (GVN)* website.

“Since my colleagues and I discovered HTLV-1 . . ., we have learned that this destructive and lethal virus is causing much devastation in communities with high prevalence,” said Robert C. Gallo, MD, co-founder and director of GVN and a professor at the University of Maryland School of Medicine in Baltimore.

“During the GVN meeting last September, I was astounded to learn of the hyper-endemic numbers in the Aboriginal population of Australia. HTLV-1 is endemic in other regions, including several islands of the Caribbean, and in countries such as Brazil, Iran, Japan, and Peru. We hope that the WHO will agree with us and begin to take action in promoting prevention strategies against HTLV-1.”

HTLV-1 prevalence

In their letter, Dr Gallo and his colleagues cite statistics of HTLV-1 prevalence around the world.

The authors note that, in a hospital-based cohort study conducted in Central Australia, 33.6% of Indigenous people tested HTLV-1 positive, with the incidence rate reaching 48.5% in older men.

Research has suggested that, in Brazil, the HTLV-1 prevalence rate is 1.8% in the general population, 1.3% in blood donors in certain regions, and 1.05% in pregnant women.

It is estimated that nearly 1 million people are HTLV-1-positive in Japan, and 850,000 to 1.7 million people in Nigeria are infected with the virus.

In Gabon, the HTLV-1 prevalence in adults is believed to be 5% to 10%. And in Central African Republic, 7% of older, female Pygmies in the southern region were found to be infected with HTLV-1.

Studies have indicated that 6.1% of the general population in Jamaica is positive for HTLV-1, and other Caribbean islands have similar prevalence rates.

The authors note that HTLV-1 and -2 have also been detected in non-endemic areas due to migration and sexual transmission.

It is estimated that 20,000 to 30,000 people are infected with HTLV-1 in the UK, and 10,000 to 25,000 people are infected in metropolitan France.

Other estimates suggest that 266,000 people are infected with HTLV-1 or -2 in the US, and 3600 people with HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) remain undiagnosed.

“The general neglect, globally, of the importance of HTLV-1 as a sexually transmitted infection that causes a range of debilitating inflammatory diseases does our patients, who request a sexual health screen, a disservice,” said Graham P. Taylor, MDMB, DSc, a professor at Imperial College London in the UK.

“It is also important to recognize the importance of mother-to-child transmission of HTLV-1 in the development of adult T-cell leukemia/lymphoma (ATLL) decades later. Despite the availability of highly sensitive and specific diagnostic tests for infection and a proven intervention, except for Japan, there are no antenatal screening programs. Evaluating the cost-effectiveness of such programs should now be a priority.”

“To prevent mother-to-child infection, the Japanese government has been offering HTLV-1 screening for all pregnant women without cost,” noted Yoshi Yamano, MD, PhD, a professor at St. Marianna University School of Medicine in Kawasaki, Japan.

“Taking a leadership role to promote research, it also provides grants for clinical trials and patient registries focused on ATLL and HAM/TSP.”

Preventing transmission

The letter outlines 5 strategies to prevent or reduce transmission of HTLV-1. The authors recommend:

  1. Protecting the sexually active population with routine HTLV-1 testing in sexual health clinics and through promotion of CMPC—Counsel & Monitor HTLV-1-positive patients, notify Partners, and promote Condom usage
  2. Protecting blood and organ donors and recipients by testing for HTLV, avoiding use of products that may be infected, and promoting CMPC
  3. Protecting mothers, babies, and fathers via routine antenatal care testing, advising HTLV-1-positive mothers against breastfeeding (when feasible), and promoting CMPC
  4. Protecting injectable drug users by promoting HTLV-1 testing, providing safe needles through needle exchange program, and promoting CMPC
  5. Supporting the general population and healthcare providers by providing access to an up-to-date WHO HTLV-1 Fact Sheet that can help healthcare providers diagnose HTLV-1 and related diseases and help patients protect themselves from HTLV-1.

“This virus has been underestimated since the time of its discovery perhaps because it is restricted to certain regions or because it is not terribly infectious,” said William Hall, MD, PhD, co-founder of GVN and a professor at the University College Dublin in Ireland.

“However, for decades, it has been known that HTLV-1 is highly carcinogenic and causes severe paralytic neurologic disease and immune disorders that can lead to bacterial infections. It is time that the WHO publicize prevention strategies against this devastating virus.”

*GVN is an international coalition of medical virologists dedicated to identifying, researching, fighting, and preventing current and emerging pandemic viruses that pose a threat to public health.

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