New computer models predict the course of an epidemic

Almost every year, we are confronted with images of poultry barns being culled to fight bird flu. Livestock farmers sometimes lose all their animals and the viruses can also pose a threat to humans. Computer models are crucial for predicting the course of such disease outbreaks so we can take effective measures before it is too late.

“When researchers observe an emerging infectious disease in a community or region, policymakers naturally want to know as soon as possible what the risk is of it spreading further and what damage to public health or to the economy they can expect,” explains infectious disease modeller Quirine ten Bosch. “They also want to know which countermeasures will likely be most effective. Computer models are helping to answer these questions.”

Collecting puzzle pieces: bird flu test case

As part of the ERRAZE@WUR programme, the modellers are trying to identify the key gaps in their knowledge: which pieces of the puzzle do they still need to find in order to quickly build accurate models during an outbreak of a new infectious disease?

Quirine ten Bosch and her colleagues are building a model for bird flu in the Netherlands as a test case. Much is already known about the transmission routes of bird flu. This often happens through migratory birds, and probably also occasional sedentary birds. Infections of poultry occur mainly during the colder periods of the year and in specific regions. Now the researchers want to better understand how different factors combine to determine the course of an epidemic. All the information they collect is fed into a computer model with which they can predict the course of infections.

This is important, because sometimes a low-pathogenic variant of the bird flu virus can turn into a highly infectious and pathogenic variant. Animals infect each other rapidly and become mortally ill. In rare cases, people can also become infected with the virus. “We know that the bird flu virus can become a threat to humans if another mammal is infected first,” says Quirine ten Bosch. “This has happened on a very few occasions elsewhere in the world, with pigs as the intermediary. The consequences can be far-reaching, as was the case with the influenza virus that was spread around the world in 2009 from pigs in Mexico.”

Model for Rift Valley fever

In addition to bird flu, the Wageningen modellers are studying Rift Valley fever, a disease that has not yet been recorded in the Netherlands. This virus is mainly found in Africa and sometimes causes high mortality among farm animals such as sheep and cattle. The virus is transmitted by mosquitoes and is also dangerous for humans. Sometimes serious complications occur in the eyes, liver and brain. However, the modellers do not yet know enough about how Rift Valley fever virus is transmitted: “What are the conditions for a major outbreak? Which animal and mosquito species play a role? What does that mean for the risks of spreading in areas where the virus does not yet exist? We are combining the available knowledge with the help of various universities and research institutes in Africa and we are also building a computer model for Rift Valley fever.”

The modellers are uncovering important information that will help to make even better predictions about the spread of the virus and the effects of interventions. “This will help us to prevent disease outbreaks in the future,” says Ten Bosch.