You’re probably already infected with a brain-eating virus you’ve never heard of

There’s a virus you may have never heard of before that is estimated to infect up to 90 percent of people and lurks silently in your cells throughout your life, but if activated, it will destroy your brain. If that’s not surprising enough, Researchers reported this week. that there may be a new way for this virus to activate, one that affects up to 10 percent of adults worldwide.

The virus is human polyomavirus 2, commonly called JC virus or John Cunningham virus, named after the poor patient from whom it was first isolated in 1971. It appears in the urine and feces of infected people and is spread by the fecal-oral route. Many people are thought to become infected at an early age, and blood test surveys have suggested that 50-90 percent of adults have been exposed at some point.

Researchers hypothesize that the initial site of infection is the tonsils or perhaps the gastrointestinal tract. But wherever it occurs, that initial infection is asymptomatic. At that moment, the person becomes infected with what is called JC archetype viruswhich silently creates a persistent but completely silent infection that lasts a lifetime.

For the vast majority of people, that’s all their JC virus infection will be: silent. But for an unlucky few, the JC virus will apparently awaken, rearrange their genetic material, and transform into a brain-destroying nightmare that causes a disease called progressive multifocal leukoencephalopathy or progressive multifocal leukoencephalopathy.

Devastating disease

In progressive multifocal leukoencephalopathy, the new disease-causing virus, or “PML-type” JC virus, actively invades the brain and destroys specific brain cells, including the cells that form the insulating myelin sheaths that protect nerve cells. This leads to extensive demyelination, resulting in nerve cell dysfunction and death. On imaging, PML may appear as characteristic lesions in the brain. Those photographed lesions, along with findings from testing for JC virus DNA in the cerebrospinal fluid, are how PML is diagnosed. But for patients suffering from PML, symptoms can mimic everything from a stroke to multiple sclerosis, causing problems such as speech problems, visual defects, motor dysfunction and seizures.

Progressive multifocal leukoencephalopathy was first identified in 1958 in a patient with cancer. But it was considered an extremely rare condition until the 1980s, when it began to be seen in patients with HIV/AIDS. In fact, PML became an AIDS-defining disease, with 2 to 5 percent of HIV-infected patients developing it in the early phase of the epidemic. At that time, the condition was uniformly fatal. But with the introduction of highly active antiretroviral therapy (HAART) in 1996, cases of PML decreased and the disease was no longer a death sentence, although survivors often suffer significant and long-lasting damage.