A large number of studies over the past 20 years have shown that there is a close relationship between climate and the dynamics of human diseases such as cholera , malaria and dengue .
Climate change, including long-term warming trends and short-term climate variability, may affect disease patterns. Xavier Rodó, a computational ecologist and climate dynamics expert at the Institute of Global Health in Barcelona and the Institute of Research and Advanced Research in Catalonia in Spain, talks to the journal Nature about how climate models can be used to help prepare for future disease outbreaks and the obstacles he faces when implementing such systems.
How does the climate affect the spread of the disease?
Climate affects the emergence and spread of diseases in many ways. Some are quite complicated. Climate conditions may have cascading effects on ecosystems, affecting the possibility of zoonotic spillovers, where pathogens jump from animal hosts to humans.
For example, we see that temperature changes in Brazil’s Atlantic forests drive a wave of yellow fever in a predictable way in howl monkeys (Alouatta species) that occur before the human epidemic in a predictable way.
As climate changes, the spread and intensity of disease outbreaks will also change. The impacts will not be the same everywhere, but changes in temperature and rainfall will lead to huge changes in the distribution and dynamics of zoonotic and vector-borne diseases.
For example, researchers have seen record numbers of mosquitoes carrying the West Nile virus in New York City, which are often found farther west.
What is the evidence that climate change affects disease outbreaks?
In a previous study, it has shown that the incidence of cholera in Bangladesh is affected by short-term climate patterns.
After the local temperature rise caused by El Niño Southern Oscillation (ENSO), the case rises in about six months, an repeated climate pattern in the warm (El Niño) and cool ( La Niño) stages that occur irregularly every 3-7 years in the Pacific.
But since the 1980s, El Niño/ Southern Oscillation has significantly intensified, and we believe that this long-term trend may also affect the incidence of cholera. Researchers studied historical cholera data spanning 70 years and found that the incidence was closely related to ENSO between 1980 and 2001.
However, the data reinforced for the previous period did not show this correlation. The long-term trend of intensifying El Niño/Southern oscillations appears to be affecting the dynamics of cholera, driven by warming.
How to use climate models to predict and prepare for disease outbreaks?
Using existing tools, in some regions, future climatic conditions can be predicted for the next season, the next summer, and even further away - some El Niño events can be predicted two years in advance. Knowing a country a few months in advance that abnormal rainy season will occur and how this may affect disease incidence, enables public health authorities to predict and plan their response. For example, they could stock up on drugs or spray pesticides in certain areas to limit the hatching of mosquitoes.
What are the obstacles to developing these prediction models ?
Climate change and Infectious Disease Epidemiology are both complex systems, and we need to bring scientists from different disciplines together to solve this problem. Now, interdisciplinary is talked about more than you see. Researchers are also facing difficulties in attracting funds for such projects, and the opportunity to publish articles in well-known journals may be limited.
researchers can train and test models for epidemiological data availability is also a problem. Regarding cholera, we have better historical data than recent data. The situation is similar for
COVID-19 – the report has dropped, so we have better data in the first two years of the pandemic than we are now. We need to understand that long-term data collection is essential if we want to be prepared for future threats.How are the development and implementation status of these tools
?
Researchers have worked with an international team to develop a model that uses El Niño predictions to predict dengue outbreaks in Ecuador . The model correctly predicts that in 2016, rising temperatures and excessive rainfall will lead to an outbreak in Machara City in March - three months earlier than expected.
It also predicts that the incidence rate is 90% more likely to exceed the average of the previous five years, and the probability of dengue outbreaks in 2019 is low.
This model and other models have been adapted for use in other regions. But these models have not been adopted by public health authorities. People say they are interesting, but they don't see direct financial benefits.
Unfortunately, saving lives has not received the attention it deserves. We have tried many times to implement our cholera prediction model in India and Bangladesh – Pasqual more than me, but have no success. The researchers also tried to establish malaria forecasting services in Madagascar , Senegal and Ethiopian , because there is abundant data there.
References
1.Rodó, X. et al. Nature Med. 27, 576–579 (2021).
2.Rodó, X. et al. Proc. Natl Acad. Sci. USA 99, 12901–12906 (2002).
3.Pascual, M. et al. Science 289, 1766–1769 (2000).
4.Lowe, R. et al. Lancet Planet. Health 1, e142–e151 (2017).
5.Petrova, D. et al. Int. J. Climatol. 41, 3813–3823 (2021).
6.Lowe, R. et al. eLife 5, e11285 (2016).
7.Laneri, K. et al. Proc. Natl Acad. Sci. USA 112, 8786–8791 (2015).
