Tuesday, May 26, 2009

Is this a Pandemic or not?

The short answer is yes.

The long answer requires an understanding of what a pandemic is.

From the Wikipedia article:

Definition

According to the World Health Organization (WHO), a pandemic can start when three conditions have been met:[1]

* Emergence of a disease new to a population.
* Agents infect humans, causing serious illness.
* Agents spread easily and sustainably among humans.

A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic, because the disease is not infectious or contagious.


This is a generic pandemic definition, and not specific to influenza.

For the case of an influenza pandemic we will add the following:


Influenza pandemics occur when a new strain of the influenza virus is transmitted to humans from another animal species. Species that are thought to be important in the emergence of new human strains are pigs, chickens and ducks. These novel strains are unaffected by any immunity people may have to older strains of human influenza and can therefore spread extremely rapidly and infect very large numbers of people. Influenza A viruses can occasionally be transmitted from wild birds to other species causing outbreaks in domestic poultry and may give rise to human influenza pandemics.


So, what are we dealing with? The novel influenzavirus A(H1N1) that is currently circulating is, by definition, a new virus in humans (though containing genetic material from previous human strains of influenzavirus type A), it definitely infects humans and can cause serious illness, and is capable of sustained spread between humans. Furthermore, it is a new virus from a different species (pigs). Therefore, despite the WHO's attempts at not declaring a full pandemic, the "classical" conditions are met.

It bears repeating, a pandemic does not have to be highly lethal, it has to infect humans in large portions of the world. The "Swine Flu" is doing just that, and the virus doesn't care what people say about it.

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