How serious is the current pandemic risk?
The risk of pandemic influenza is serious. With the H5N1 virus now firmly established in large parts of Asia, the risk of more human cases will persist. Each additional human case gives the virus an opportunity to mutate, and thus develop into a pandemic strain. The spread of the virus to poultry and wild birds in new areas creates additional opportunities for human cases to occur. While nobody can predict the timing and severity of an outbreak, the probability that a pandemic will occur has increased over time.
The risk of pandemic influenza is serious. With the H5N1 virus now firmly entrenched in large parts of Asia, the risk that more human cases will occur will persist. Each additional human case gives the virus an opportunity to improve its transmissibility in humans, and thus develop into a pandemic strain. The recent spread of the virus to poultry and wild birds in new areas further broadens opportunities for human cases to occur. While neither the timing nor the severity of the next pandemic can be predicted, the probability that a pandemic will occur has increased.
The risk of pandemic influenza is serious. With the H5N1 virus now firmly entrenched in large parts of Asia, the risk that more human cases will occur will persist. Each additional human case gives the virus an opportunity to improve its transmissibility in humans, and thus develop into a pandemic strain. The recent spread of the virus to poultry and wild birds in new areas further broadens opportunities for human cases to occur. While neither the timing nor the severity of the next pandemic can be predicted, the probability that a pandemic will occur has increased.
To date, there have been just over 200 cases reported in humans since 1997, although the case fatality rate (over 55 percent) is high. In contrast, each year about 7.5 percent to 8 percent of all deaths in the United States are related to seasonal influenza or pneumonia. I think this puts things into perspective. Right now, there is very little evidence that supports direct person-to-person spread of avian influenza. These are bird-adapted, not human-adapted, viruses. But the possibility remains that these viruses could adapt, change and become easily contagious to humans while retaining their ability to cause high fatality rates. What would be some warning signs that a pandemic is about to start? The warning signs would be based on laboratory detection, or what we call laboratory surveillance.
The H5N1 virus is now firmly entrenched in poultry in large parts of Asia. As a result, more human cases will occur and provide the virus increasing opportunities for “reassortment”, increasing the risk of the emergence of an easily transmissible human pandemic strain. The recent spread in wild birds and poultry to new areas also allows increased opportunities for human cases to arise in an expanding geographic range, increasing the probability that a pandemic will occur.
