MASSACHUSETTS NURSE NEWSLETTER :: July/August 2005

The avian influenza threat

A report by the World Health Organization in Geneva presented these dire findings about avian influenza and the potential for a pandemic:

• No virus of the H5 subtype probably has ever circulated among humans, and certainly not within the lifetime of today’s world population. Population vulnerability to an H5N1-like pandemic virus would be universal.
• Many of the public health interventions that successfully contained severe acute respiratory syndrome will not be effective against a disease that is far more contagious, has a very short incubation period, and can be transmitted prior to the onset of symptoms.
• Evidence strongly indicates that H5N1 now is endemic in parts of Asia, having established a permanent ecological niche in poultry. The risk of further human cases will continue, as will opportunities for a pandemic virus to emerge.
• Studies comparing virus samples over time show H5N1 has become progressively more pathogenic in poultry and in the mammalian mouse model, and now is hardier than in the past, surviving several days longer in the environment. Evidence further suggests H5N1 is expanding its mammalian host range.
• Recent publications have suggested...similarities between H5N1 and the 1918 virus in the severity of disease, its concentration in the young and healthy, and the occurrence of primary viral pneumonia in the absence of secondary bacterial infection.
• All prerequisites for the start of a pandemic have been met save one, namely the onset of efficient human-to-human transmission. Should the virus improve its transmissibility, everyone in the world would be vulnerable to infection by a pathogen passed along by a cough or a sneeze—entirely foreign to the human immune system.