HTLV-1 is a virus that hardly anyone in Germany knows about. It usually causes no symptoms, but it can trigger blood cancer and other diseases. HTLV-1 is the name of a virus that is comparatively unknown. This is hard to believe, considering that HTLV-1 can cause a severe form of cancer. But the discovery of the virus came at a time when scientific interest was focused on a much more pressing problem: research into HIV. Today, the virus has spread almost unnoticed in some parts of the world – no vaccine or cure exists. Read what is known about HTLV-1 infection and its transmission here.
What is HTLV-1?
The abbreviation HTLV stands for human T-lymphotropic virus. It is a so-called retrovirus, i.e., a virus that is able to modify its own genetic material so that it can integrate into the DNA of its host and thus alter its genetic material. This enables it to cause cancer, for example. Various closely related virus types are grouped under the name HTLV. HTLV-1 (also: HTLV-I or human T-lymphotropic virus 1) is type 1, the first to be discovered and also the most important form. Previously, the name “human T-cell leukemia virus type 1″ was also used.
HTLV-1: unknown and unexplored.
HTLV-1 was discovered back in 1980 by researcher Robert Gallo and his team. This discovery was a sensation, because no retroviruses had previously been known in humans. A short time later, however, the human immunodeficiency virus HIV, the cause of AIDS, was discovered. This retrovirus, which is related to HTLV-1, was initially named HTLV-3 and quickly slipped into the focus of science due to its rapidly increasing spread. Research on HTLV-1 fell into the background and almost into oblivion – as a result, the virus is not even known to many today.
How dangerous is HTLV-1?
Many people infected with HTLV-1 do not even know about their infection, because in most cases it causes no symptoms. But for about ten percent of those affected, the infection takes a severe course:
- The virus is considered one of the possible triggers of a certain form of blood cancer. In up to five percent of those affected, it causes adult T-cell leukemia (ATL), a tumor disease with a very short life expectancy.
- About three percent of those infected develop Tropical Spastic Paresis (also known as HTLV-1-associated myelopathy). This is a neurological degenerative disease of the spinal cord.
- Also, a study showed that many affected people suffer from bronchiectasis, a pathological dilation of the bronchial tubes. Whether HTLV-1 is actually responsible for this lung condition has not yet been determined.
- Other possible consequences include inflammation of the skin (dermatitis), eyes (uveitis), joints (arthritis) and muscles (myositis), as well as a weakening of the immune system.
Many affected individuals carry the virus for several decades before symptoms of disease appear.
Transmission of the virus
HTLV, like HIV, is primarily transmitted through sexual intercourse – scientists believe this route of transmission accounts for about 80 percent of cases. However, transmission from a mother to her child through breast milk is possible, as is infection through a blood transfusion (blood plasma is not considered infectious) or an organ transplant. Sharing syringes among drug addicts is also a possible route of transmission.
Diagnosis and treatment of HTLV-1 infection.
Once the virus enters the body, it remains there for life. Diagnosis is based on a blood test: if the test shows antibodies (IgG – immunoglobin-G) against HTLV-1, this serves as proof that the virus is present in the organism. This is called a positive HTLV-1 serology. There is currently no cure for the viral infection. Therapy is used exclusively to treat the secondary diseases mentioned above.
How can you protect yourself?
There is no vaccination against HTLV-1. Similar to HIV, the use of condoms helps to prevent transmission through sexual intercourse. Infected mothers should refrain from breastfeeding their children – in Japan, this drastically reduced the number of new infections. In addition, infected persons should not donate blood, sperm, organs or other tissue.
Spread of the virus
Human T-lymphotropic virus type 1 is rarely seen in Europe, with the exception of Great Britain. In Australia, it is more common, especially among Aborigines: A 2016 study among Aboriginal Australians showed that nearly one in two men older than 50 carried the virus. Endemic areas also include:
- The south of Japan
- The Caribbean
- Iran
- Parts of Africa
- Certain regions in South America (for example, Brazil)
- The United States (where HTLV-2 plays the greater role and is particularly prevalent among certain populations).
How many people are infected?
It is thought that between 10 and 20 million people worldwide are currently infected with the virus – women are generally more likely to be affected. How many cancer cases are attributable to HTLV-1 each year is disputed. Estimates range from 3,000 to 10,000 cases worldwide per year. In Germany, the infection is diagnosed in only a few people. However, due to the low prevalence, testing for the virus is not standard practice in humans or for blood transfusions or donor organs, so no usable figures are available. However, the risk of infection is considered low.
Other types of HTLV
In addition to HTLV-1, there are other types of human T-lymphotropic virus. HTLV-2 (also: HTLV-II) was also discovered by Robert Gallo’s research group. The role of the virus in the development of human diseases has not yet been clarified. The number of infected persons is also significantly lower than with HTLV-1, which is why this virus type is considered to be of lesser importance. HTLV-3 was initially the name of the HI virus, but is no longer used in this context. Today, HTLV-3 (or: HTLV-III) and HTLV-4 (also: HTLV-IV) are two viruses closely related to HTLV-1 and 2, which were discovered in Cameroon in 2005. Nothing is yet known about the spread and potential threat of these viruses.
