Feb 23, 2006

Mutation Rate Of Zoonotic Diseases Rising Rapidly


The mutation of animal diseases that can infect humans is rising at an "unsustainable rate," with the arrival of one new pathogen capable of causing infectious diseases reported per year over the past 25 years, according to a survery conducted by Mark Woolhouse, of the University of Edinburgh.

"The human population is accumulating novel pathogens at a rate of more than one new species per year, plus a host of variants of existing pathogens," said Woolhouse yesterday. "This does not seem to be sustainable over evolutionary timescales; we would be overrun with pathogens."

About two-thirds of the new human pathogens are RNA viruses, which have a smaller number of genes, making them more susceptible to mutation. There are more than 1,400 different pathogens that can infect humans, and Woolhouse said that 58 percent of those are zoonotic (animal in origin, with or without direct transmission).

Avian flu, more properly the H5N1 virus, is just the latest in zoonotic diseases. Tuberculosis, malaria, and smallpox made the jump from animals to humans thousands of years ago, while more recent zoonoses include SARS, Ebola, and Rift Valley fever.

The key to managing emergent zoonoses, according to Woolhouse, is surveillance.

"We have to expect the unexpected, making sure that effective surveillance is in place to detect and, if necessary, act upon unusual infectious disease events," he said. "Human infectious diseases do not evolve in isolation, but have strong epidemiological and evolutionary links with infectious diseases of other animals."


Anonymous said...

Do we have anything to worry about?

historymike said...

The problem in tracking the number of human pathogens is that we only have a few decades by which we can measure.

Certainly the growth in the number of harmful diseases is not good news, but is this a cyclical phenomenon?

I don't know that anyone has the answers yet, but just how dangerous some of these new pathogens will be is anyone's guess.

I tend toward a pessimistic view of human ability to "conquer" disease. I suspect that microbes will win many battles against humans over the course of several millenia.

My best guess? There are probably periods of stasis and periods of imbalance between people and microbes, and we are probably headed into one of those unbalanced periods now.

Name withheld to protect the guilty said...

Funny that they point out one each year for the last 25...since that corresponds pretty well with the length of time we've been able to do rudimentary DNA/RNA sequencing.

It probably has more to do, as they pointed out, with our mobile society than anything else. If a pathogen jumped just 150 years ago, it probably would have hit one village, then died out, unless it had truly novel characteristics that could help it spread, like smallpox etc.

historymike said...

Imagine if Ebola made it to a major city - yikes!

It could circle the globe in a week, two weeks tops.

Name withheld to protect the guilty said...

Yet it won't. Ebola is actually pretty hard to catch in countries with decent sanitation.

At least in its present form.

Its present form is fairly unlikely to change, however, because a disease that kills people that quickly won't spread as effectively as one that takes a while to kill. Note HIV, which is a ridiculously fragile virus, quite difficult to catch (something like 100x less virulent than Hepatitis B virus), but has spread quite effectively.

Stephanie said...

You say "unsustainable" a lot. What did you mean? The diseases are unsustainable? The animals are unsustainable? The rate of growth is unsustainable? We're unsustainable? I'm not panicking, but clarification would be appreciated.

(As a sci-fi aficiando unsustainable usually means somethings going to explode, implode, or when bad science is involved, both.)