Bangalore: As if viruses haven’t sprung enough surprises on the world this year, jumping from pigs to humans to create the swine flu epidemic scare, scientists have now stumbled upon a new one that’s present in two-thirds of people suffering from chronic fatigue syndrome (CFS), a debilitating disease whose causes are unknown even though it affects at least 1% of the world population.
In Friday’s issue of Science, a team of researchers from the US reports that they have uncovered the human retrovirus XMRV (xenotropic murine leukaemia virus) in the blood samples of CFS patients and concludes that the virus has a role to play in the cause and progression of the disease.
New dimension: An electron micrograph of the virus XMRV detected in a patient with chronic fatigue syndrome. Whittemore Peterson Institute
What precisely that role is, is still unclear, experts say.
Deciphering this is the next immediate goal.
“I anticipate there will be a rush to do more extensive studies of its origin, distribution and mode of transmission…studies examining association with prostate cancer, CFS and other tumours, and seek to understand possible mechanism of disease induction,” says Jonathan P. Stoye, a virologist at the National Institute for Medical Research in London.
The virus was recently found to be present in about 25% of prostate cancers and the two viral strains are 99% similar genetically, which, researchers say indicates that there aren’t many strains of XMRV and that it isn’t evolving as fast as its more complex viral kin HIV is.
Interestingly, the virus is also found in healthy populations. The association is the same as in HIV and AIDS, says lead author Judy A. Mikovits, research director at Whittemore Peterson Institute, University of Nevada, Reno. “You can be infected with HIV without having AIDS, but you cannot have AIDS without having HIV.”
Listen to Sunit Kumar Singh from the Centre for Cellular & Molecular Biology at Hyderabad talk about the virus
This is a remarkable finding, says Sunit Singh, a scientist at the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad. The cause of CFS, where fatigue persists for years and doesn’t end with rest, has been unknown for a long time. “This research has really given a new dimension in understanding the mechanism of this CFS. No one would have believed earlier that CFS is linked with the viral infection.”
Still, the finding throws up more questions than it answers, and will probably lead to several studies worldwide looking for diseases with similar symptoms.
Researchers are convinced that the medical implications are immense.
“In terms of treatment, it means that any CFS patient with XMRV will be classified as having an infectious disease, and not a psychiatric one,” says Mikovits. She thinks this gives the medical community a therapeutic target to begin testing the existing antiretrovirals and non-steroidal anti-inflammatory drugs. The key to look for is the virus and the infected individuals’ immune response to it, just as in HIV, where difference in immune response is vital for the disease management, she explains.
Chronic fatigue, which affects multiple organs and causes abnormalities in the body’s immune system function, is largely studied in the developed world where a large proportion of the patients have medically “unexplained physical symptoms”. There are hardly any epidemiological data from countries such as India where one in eight women report chronic fatigue.
However, in 2005, a study published in the British Medical Journal, designed to look at CFS—which has often been attributed to nutritional deficiencies and anaemia in the developing world—concluded that in developing countries, the disease is “strongly” associated with mental illness. The study sampled 3,000 women in Goa.
Medical practitioners use a mix of drugs and counselling to treat such patients. “We see a large number of CFS patients and use psycho-counselling as well as drugs like pregabalin (meant for relieving neuropathic pain),” says Neeraj Jain, a consultant with Sir Ganga Ram Hospital in New Delhi. “I agree there could be an association with CFS and XMRV, but it needs a lot of work since even healthy population is also seen to be infected.”
Initially, the study found 3.5% of the US population to be infected. Later another study showed Tokyo with a 1.7% infection rate, says Mikovits. Experts don’t think race and ethnicity have anything to do with the ability to be infected, but Stoye believes it is important to test whether XMRV is present in people of different races from different parts of the world.
Since CFS badly affects the mobility and lifestyle of people, we need to understand the co-infection in the case of XMRV progression, says CCMB’s Singh. “While it may not be a bad idea to conduct large-scale screening, we should at least screen those with CFS-like symptoms in India.”