London: Scientists have successfully developed a model that can predict the outbreak of diseases that spread from animals to humans - such as Ebola and Zika - based on changes in climate, population growth and land use.
"This model is a major improvement in our understanding of the spread of diseases from animals to people," said Kate Jones from University College London (UCL) in the UK. "We hope it can be used to help communities prepare and respond to disease outbreaks, as well as to make decisions about environmental change factors that may be within their control," said Jones.
More than 60 per cent of emerging infectious diseases are zoonotic and although Ebola and Zika are well-known, there are many other diseases including Rift Valley fever and Lassa fever which affect thousands already and are predicted to
spread with changing environmental factors, researchers said. Lassa fever is endemic across West Africa and is caused by Lassa virus passing to people from rats. The model predicts the number of people with the disease will double from 195,125 to 406,725 by 2070 due to climate change and a growing human population.
Like Ebola virus, Lassa virus causes haemorrhagic fever and can be fatal. How many people are affected by Lassa fever each year is unclear as many do not have severe symptoms and those that do are often misdiagnosed with malaria. Current estimates range from 100,000 to one million, researchers said. "Our new approach successfully predicts outbreaks of individual diseases by pairing the changes in the host's distribution as the environment changes with the mechanics of how that disease spreads from animals to people, which has not
been done before," said David Redding from UCL.
"Importantly, the model also has the potential to look at the impact of global change on many diseases at once, to understand any trade-offs that decision-makers may have to be make," added Jones. Researchers used the locations of 408 known Lassa fever outbreaks in West Africa between 1967-2012 and the changes in land use and crop yields, temperature and rainfall, behaviour
and access to healthcare.
They also identified the sub-species of the multimammate rat (Mastomys natalensis) which transmits Lassa virus to humans to map its location against ecological factors. The model was then developed using this information along
with forecasts of climate change, future population density and land-use change, researchers said. The approach has already proved successful by predicting
the current disease patterns of Lassa fever.
Researchers say the model could be refined to consider zoonotic disease transmission within human populations by including the impact of travel infrastructure, human-to-human contact rates and poverty - something that would have been of enormous use in the recent Ebola and Zika outbreaks. The findings were published in the journal Methods in Ecology and Evolution.
