Disease Mutations

I was reading this article about the Ebola outbreak in Uganda, and noticed this part:

However, Museveni said that the virus had not been immediately identified this time, resulting in a delay.

"The bleeding which normally accompanies Ebola did not take place initially among these patients," he said, adding that health workers at first did not therefore realise what the problem was.

"Because of that delay the sickness spread."  

Unfortunately, there is little more information. So we don't know if the lack of bleeding was due to a particular strain of the virus, coincidence among the victims, or some other factor at play here. One of the problems that the Ebola virus faces is that it is so lethal that its victims die before they can pass the disease on. Historically, between mutations in a virus or bacteria, and increased immunity in the population, many diseases have become less virulent over time in order to more easily propagate. Perhaps this is a sign of a slightly less deadly version of Ebola that would, for that reason, more easily spread.

On a related note, there is this story of bird flu crossing over to seals, suggesting that it could infect other mammals.

It's a virus that originated in birds, but the newest strain of avian flu has killed 162 harbor seals in New England and scientists warn it could be even more dangerous if it jumps to humans.

Researchers revealed on Tuesday that the aquatic mammals, which washed up dead or dying on the shores of Maine and northern Massachusetts last fall, were infected with the H3N8 strain of influenza.

The seals suffered horrifying skin lesions, a previously unknown symptom in flu deaths, and pneumonia as a result of a virus that they contracted from North American waterfowl, according to researchers at Columbia University.

Even more worrying is the fact that the virus has mutated to develop the ability to infect the cells of mammals -- a first for the avian pathogen.

The story also mentions that there have been several outbreaks of swine flu in the United States.