There is a risk that the virus that causes bird flu could develop into a new form that could spread rapidly from person to person, potentially causing a pandemic. A new model incorporated in a software environment called SEARUMS1, combines data on waterfowl migration with information on which waterfowl species are at greater risk of carrying the virus and information on the global poultry population (an estimated 18.136 billion birds). It also looks at distribution of poultry populations and global human population data (estimated at 6.646 billion people). By assuming seasonal waterfowl migration is the main cause of the spread of the virus, the model allows scenario planning for outbreaks in poultry flocks with possible transmission of the virus to humans.
Three case studies examined the impact of avian influenza in the United States. In all instances, it was assumed that there would be minimal human-to-human infections. Results from the study suggest:
- the occurrence of avian influenza in the US is inevitable: the timing and routes of waterfowl's migratory flights determine when the virus arrives and how it spreads. The number of infected birds in these flocks is not an influencing factor.
- where infected waterfowl or poultry were the source of infections, it is unlikely there would be a pandemic, although there would be human illnesses and fatalities. It is predicted that the virus would enter via coastal areas and the whole of the US would be affected in cycles coinciding with the annual migration of waterfowl.
- the socio-economic impacts of outbreaks can be estimated through the loss of poultry. Costs arise from: human infections and deaths, the need to cull large numbers of poultry to control the spread of the disease and the consequent loss of income from domestic and export markets, reduced tourism revenues and the negative effects on biodiversity. The study showed that poultry populations fluctuated with the migratory patterns of waterfowl, with poultry stocks regenerating between outbreaks.
SEARUMS can be used as a global collaborative tool by epidemiologists, governments and economists. Organisations responsible for controlling outbreaks could use SEARUMS, in conjunction with, for example, the World Health Organisation's preparedness plan2 to co-ordinate the distribution of vaccines to affected areas in order to save lives and avoid a pandemic.