The association of weather with infectious diseases can help in creating an early warning system for outbreaks.
Researchers at the Mailman School of Public Health at Columbia University conducted a study to find out what causes outbreaks of very dangerous diarrhea for young children. Article about it published In the magazine Nature communications.
In low- and middle-income countries, diarrhea is the second leading cause of death among children under five. Almost three quarters (72%) of deaths occur in babies from birth to two years. Mortality rates are particularly high in Africa.
The frequency of the disease can also be affected by weather changes. Previously, a correlation was recorded between fluctuations in climatic changes caused by the warm El Niño and surges in incidence in Peru, Bangladesh, China and Japan. The authors decided to check whether there is a connection between outbreaks of diarrhea in Africa and the El Niño antipode, the cold current of La Niña. Previously, work on climate and incidence in African countries recorded only association with cholera, which accounts for only a fraction of the dangerous intestinal diseases on the continent.
The so-called Southern Oscillation consists of the phenomena of El Nino and La Nino, causing opposite extreme indicators of water temperature and atmospheric pressure in the equatorial zone of the Pacific Ocean. The periods in which they dominate last for six months, and such changes occur every few years, from three to seven. Between them several years can pass without weather disasters. Both phenomena affect the climatic state of the entire planet, but the most severe consequences appear near the main “theater of action”.
The authors analyzed the relationship between the status of the Southern Oscillation, climatic conditions, and cases of diarrhea in children under the age of five in the Chobe region in northeastern Botswana. They found that La Niña is associated with lower temperatures, increased rainfall and increased floods during the rainy season. In turn, these weather conditions caused by La Niña, with a delay of up to seven months, give a connection with an approximately 30% increase in the incidence of diarrhea in children of this age. all this happens at the beginning of the rainy season – from December to February.
Scientists explain that these results show that forecasts for the phenomena of the Southern Oscillation can be used as a tool for predicting epidemics of intestinal diseases of various etiologies – at least in the countries of southern Africa. Infectious diarrhea is caused by many different pathogens – viruses, bacteria and protozoa, and weather conditions can critically affect their activity, especially those transmitted through water. For example, heavy rains pollute drinking water, bringing pathogens from pastures and from infected dwellings to water storages, and drought provokes the accumulation of animal carriers at water bodies, increasing the entry of microorganisms into surface water resources.
Given the changing climate of these places and the lack of water purification systems, scientists recommend conducting additional research and using their results to deal with possible epidemics. In addition, such relations with climate events are important not only for countries in Africa: for example, similar models are built even in the USA, though not for intestinal infections, but in the flu season. Models are also used to predict the spread in various places of deadly diseases such as the Ebola virus and West Nile virus.
Scientists hope that long-term results can help save many lives. They can form the basis of an early warning system. It will allow officials of local ministries of health to prepare for periods of increased incidence of diarrhea in advance: up to seven months can elapse from the moment the first data is received until the epidemic begins. “Increased stocks of medicines, the preparation of hospital beds and the organization of health workers can significantly improve the ability of medical facilities to cope with the high incidence of diarrhea,” they explain.