Diseases evolve rapidly to become more - or less - virulent

Virginia Polytechnic Institute and State University researchers have investigated why pathogens cause harm to the hosts they depend on in order to better understand virulent diseases.

The study looked at house finch eye disease - a form of conjunctivitis caused by Mycoplasma gallisepticum bacteria - which is not harmful to humans, with the expectation that virulent diseases become milder over time to improve spreadability.

Studying frozen bacterial samples taken from sick birds in California and the Eastern Seaboard between 1994 and 2010, researchers found that the disease had evolved a higher virulence over time in some bird populations.

It was also found that the same disease had become less virulent in other finches, allowing for it to spread great distances.

Read more at Virginia Polytechnic Institute and State University