With about 60 countries and territories worldwide reporting active Zika virus transmission, predicting the global spread of the mosquito-borne illness has been challenging for public health officials.
However, researchers are leveraging large-scale computational models that integrate socio-demographic and travel data as well as simulations of infection transmission—requiring the computing power of 30,000 processors simultaneously—to project the path of the disease.
The Global Epidemic and Mobility (GLEaM) model has been used in the past to simulate the spread of Ebola, H1N1 flu, and other outbreaks on a worldwide scale. However, in forecasting Zika, researchers have relied more on the historical patterns of mosquito-borne diseases such as chikungunya and dengue.
While the Zika virus can also be transmitted sexually, their computer model does not take that mode of transmission into consideration. They describe the Zika virus epidemic as “characterized by slow growth and high spatial and seasonal heterogeneity, attributable to the dynamics of the mosquito vector and to the characteristics and mobility of the human populations.”
In fact, mosquitoes bring an added level of difficulty to the equation, given the uncertainty of their travel behaviors, abundance and lifecycle depending on temperature, as well as the relationship between Zika and its host mosquitoes.
According to Alessandro Vespignani, professor of physics and director of the Network Science Institute at Northeastern University, what makes Zika such a challenge to track and predict is that as many as 80 percent of people infected with the virus are asymptomatic, and it is primarily transmitted by mosquitoes and spread internationally through travel.
But by combining real-world data on populations, human mobility and climate with elaborate stochastic models of disease transmission, a team of 14 researchers—half drawn from Northeastern—has devised projections for the number of Zika cases in the Americas through January 2017.
“Whatever the disease surveillance systems tell us, it is just the tip of the iceberg,” contends Vespignani.