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There is a recent article on Independent.co.uk that reports on some apparent changes in the H5N1 bird flu virus that are causing some concerns in the World Health Organizations. The virus is apparently becoming more dangerous by becoming less lethal.

The H5N1 flu virus apparently originated in Southeast Asia. It has certainly caused the most deaths in countries in that region with a death rate of about 50% of the infected population. Fortunately, the disease has not developed the ability to be easily transmitted to humans or between humans, so the infection rate and the total number of deaths have been relatively low.

Outside of Southeast Asia, the country with the highest number of H5N1 infections has been Egypt. According to the Independent article there has also been a change in the infection pattern and the fatality rate in that country. Both of these are indications that the virus is evolving; a not unexpected occurrence given the high mutation rate in the flu virus in general.

Infection Pattern

The first oddity in the infection pattern is that most of the infected patients are children; in Southeast Asia the infected patients are a virtual cross section of the exposed community. While children are more vulnerable to viral infections because of their less developed immune system, that would typically result in a higher complication or mortality rate for children not a significantly higher infection rate.

What WHO authorities are afraid of is that they are not identifying the infected people in the remainder of the population because they are not requiring medical treatment. This is called having a sub-clinical infection'. With a rise in the number of sub-clinical infections the probability of human-to-human transmission rises. Human-to-human transmission is a pre-requisite for a flu pandemic.

Changes in Mortality Rate

So far, the death rate from the Egyptian version of the H5N1 virus is much lower than 50%. While this is good news for those infected with the virus, this also raises concerns in the medical community. If a pandemic were to start with this strain of the flu virus and it had a 50% mortality rate, it would be much easier to get the vast majority of people to comply with preventive measures. If it were much lower than 50%, more people would not worry much about the virus and they would be less likely to take appropriate precautions to prevent the spread of the resulting illness. Just look at the low rate of flu vaccine use in the United States.

As the article points out in its closing sentence: "Studies show that an outbreak that killed as few as 5 per cent of those it infected could still cause hundreds of millions of deaths around the world."

Learn more about this author, Patrick Coyle.
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