2015-2016 El Nino has triggered outbreaks around the world

El Niño is an irregularly recurrent climate pattern characterized by warmer than usual ocean temperatures in the equatorial Pacific Ocean, which creates a knock-on effect of anticipated climate change in regions far away from Earth. During the 2015-2016 event, changes in precipitation, surface temperature and vegetation created and facilitated conditions conducive to disease transmission, resulting in an increase in reported cases of plague and diarrhea. Hantavirus in Colorado and New Mexico, cholera in Tanzania, and dengue fever in Brazil and Southeast Asia, among others.

"The strength of this El Niño was among the top three of the past 50 years, and the impact on weather conditions and therefore diseases in these regions was particularly pronounced," said lead author Assaf. Anyamba, a researcher at NASA's Goddard Space Flight Center. in the Greenbelt, Maryland. "By analyzing satellite data and modeling to track climate anomalies, as well as public health records, we were able to quantify this relationship."

The study used a number of climate data sets, including surface temperature data and surface of the medium resolution imaging spectroradiometer on NASA's Terra satellite, as well as precipitation datasets from NASA and the National Oceanic and Atmospheric Administration. The study was published February 13 in the journal Nature. Scientific reports.

According to monthly epidemic data from 2002 to 2016 in Colorado and New Mexico, reported plague cases reached their highest level in 2015, while the number of hantavirus cases reached its culminating point in 2016. The cause of the rise of these two potentially life-threatening diseases was the increase in rainfall and warmer temperatures caused by El Niño in the southwestern US stimulated vegetative growth and provided more food to rodents carrying hantavirus. The resultant rodent explosion put them in more frequent contact with humans, who contract the life-threatening disease mainly through fecal or urinary contamination. While their rodent hosts proliferated, flea vectors also

A further continent in Tanzania's eastern Tanzania, the number of reported cases of cholera in 2015 and 2016 was respectively the second and the third highest, over an 18-year period from 2000 to 2017. Cholera is an infection potentially fatal bacterial of the small intestine that is spread by fecal contamination of food and water. Increased rainfall in East Africa during El Niño allowed sewage to contaminate local water sources, such as untreated drinking water. "Cholera does not disappear quickly from the system," Anyamba said. "Even though it's been magnified in 2015-2016, it has actually continued in 2017 and 2018. We're talking about a sustainable, long-term spike."

In Brazil and South-East Asia, El Niño dengue fever has proliferated. In Brazil, the number of reported cases for the potentially lethal disease transmitted by mosquitoes in 2015 was the highest between 2000 and 2017. In Southeast Asia, namely Indonesia and Thailand, the number of cases reported, although relatively low for an El Niño year, was even higher than the neutral years. In both regions, El Niño produced higher than normal surface water temperatures and, as a result, drier habitats, attracting mosquitoes to populated urban areas containing the open water required for spawning. When the air warmed up, the mosquitoes also became more hungry and reached sexual maturity more quickly, which resulted in an increase in mosquito bites.

The close relationship between El Niño events and epidemics underscores the importance of existing seasonal forecasts, said Anyamba, who has been involved in this type of work for 20 years thanks to funding from the US Department of Defense. Countries where these outbreaks occur, as well as the World Health Organization and the Food and Agriculture Organization of the United Nations, can use these predictions to take preventive measures to minimize the spread of the disease. On the basis of forecasts, the US Department of Defense establishes pre-deployment planning and the US Department of Agriculture (USDA) takes steps to ensure the safety of imported goods.

"Knowledge of the linkages between El Niño events and these important human and animal diseases generated by this study is essential for disease control and prevention, which will also mitigate globalization," said the co-ordinator. author Kenneth Linthicum, director of the USDA center in an entomology laboratory in Gainesville, Florida. He noted that these data were used in 2016 to prevent an outbreak of Rift Valley fever in East Africa. "By vaccinating the cattle, they have probably avoided thousands of human cases and animal deaths."

"This is a great tool to help people prepare for and anticipate impending illnesses," said co-author William Karesh, Executive Vice President of Health and Safety. EcoHealth Alliance for Public Health and the Environment in New York. "Vaccination of humans and livestock, pest control programs, elimination of excess stagnant water are some of the measures that countries can take to minimize their However, for many countries, particularly the agricultural sectors in Africa and Asia, these forecasts are a new tool for them, so it may take time and resources for this type of practices be used more. "

According to Anyamba, the main advantage of these seasonal forecasts is the weather. "Many diseases, including mosquito-borne epidemics, have a response time of two to three months after these climate changes," he said. "The seasonal forecasts are therefore very good and their monthly update allows us to follow the conditions in different places and prepare ourselves accordingly.It has the power to save lives."

Explore further:
El Nino changes the geographical distribution of cholera cases in Africa

More information:
Assaf Anyamba et al, World outbreaks of diseases associated with the 2015-2016 El Niño event, Scientific reports (2019). DOI: 10.1038 / s41598-018-38034-z