Can A Virus Make You Dumber?

That might be a possible indication of a recent study of the virus ATCV-1 done by pediatric infectious disease expert Robert Yolken and his team at Johns Hopkins University School of Medicine in Baltimore, Maryland. Chlorovirus ATCV-1 is a virus that typically infects a species of green algae found in lakes and rivers. However, it has recently been found in the brain tissue of human corpses and in the throats of people with psychiatric disease. And ATCV-1 doesn't just appear in humans who are ill or dead. The Johns Hopkins study found that in a sample of 92 healthy study participants, 43% of them had the virus. The participants who had the virus did significantly worse on tasks measuring cognitive functioning, including visual processing and attention span.

While Yolken and his colleagues controlled for factors such as age, sex, race, and education level in their study, the initial association they had found did not necessarily prove that the virus is the direct cause of the cognitive impairment. The presence of the virus might instead be an indicator of the presence of some third variable which is actually causing the cognitive decline. The researchers point out that it might mean the virus might just be taking advantage of the presence of some other factor that impairs the brain in some people, such as other infectious agents, heavy metals, or pollutants, the researchers say.

To determine causality, the team injected uninfected and infected green algae into the mouths of mice, knowing that infected mice would produce detectable antibodies. Both sets of mice were then put trough a series of cognitive tasks. Infected animals had poorer attention spans and they weren't as good as uninfected mice at remembering their surroundings. Though the virus has not yet been found in the brain itself, Yolken and the other researchers also looked at the hippocampi of both groups of mice and found that in the infected mice there had been changes in the activity of almost 1300 genes in the hippocampus, which is involved in memory.

How does the virus come to be present in the human body in the first place? Yolken and his team have not fully determined exactly how the virus infects people, but it turns out that ATCV-1 is just one of many microorganisms that inhabit human mucosal tissue, and it is found in algae in inland waters worldwide. As the researchers remark in their paper, the study indicates that "viruses in the environment not thought to infect humans can have biological effects".

By Kasiemobi Udo-okoye

Reference: http://www.pnas.org/content/early/2014/10/23/1418895111.full.pdf+html