Transmission Patterns of Infectious Diseases Change
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JAKARTA, KOMPAS – Global warming has contributed to changing patterns in the transmission of infectious diseases, especially those spread by insect vectors like mosquitoes. This change has also begun to appear in Indonesia, although data on it is still limited.
"Climate change has triggered increased mosquito activity. Warmer temperatures make mosquitoes more active. Global warming has caused warming temperatures in areas that previously did not support the mosquito breeding cycle, so mosquitoes are now breeding more quickly," Tedjo Sasmono, the dengue laboratory head at the Eijkman Molecular Biology Institute, said in Jakarta on Wednesday.
Indonesia is currently seeing an increase in the number of dengue hemorrhagic fever (DHF) cases in highland regions that once had cooler climates. According to Kompas records, DHF spread in several areas early this year, including the cities of Bogor and Sukabumi in West Java, as well as Temanggung regency in Central Java.
Sukmal Fahri’s 2013 study, published in the PLOS Neglected Tropical Diseases peer-reviewed journal, found the dengue virus at 1,001 meters above sea level in some areas of Central Java. Eijkman’s senior malaria and mosquito researcher Syafruddin, who was involved in the study, said it proved that the transmission of dengue fever through mosquitoes was expanding.
Mosquitoes are highly adaptable. Changes in climate patterns change the distribution of disease vectors in an area. Mosquitoes are widespread across the globe. However, the vector’s spread in the tropics is changing. "Only those that adapt can survive," said Syafruddin.
Changing climate patterns had triggered the emergence of several diseases whose causes were still unknown, but were thought to be transmitted by mosquitoes. "We have observed a number of cases, such as in South Sulawesi, of many vector-borne diseases with flu-like symptoms," he said.
In addition, the composition of mosquito species and the diseases they transmit have also changed. Malaria has declined, but DHF is increasing along with several other types of mosquito-borne diseases, such as chikungunya, elephantiasis and Zika. "Our study on Sumba Island found 11 species of the Anopheles genus of mosquitoes, which transmits malaria," he said.
Several foreign studies have linked changes in the transmission patterns of mosquito-borne diseases to weather phenomena like La Niña and El Niño. J. Fan’s 2014 study in Guangdong Province, China, for example, found a connection between El Niño and dengue transmission. Chen\'s 2010 study found that increased air humidity in 2005 due to El Niño in Kaohsiung, Taiwan, had accelerated the mosquito breeding cycle.
Tedjo said that, from his observations, Indonesia had a low number of dengue cases two years after the 2015 El Niño. "No scientific data has been published about this, even though it is important to understand changes in disease patterns in connection with climate change trends," he said.
Fly transmission
Climate change has also increased the transmission of fly-borne diseases. A recent epidemiological study from Canada’s Waterloo University that was published on Feb. 13, 2019 in Royal Society Open Science stated that global warming had increased the activity of the housefly, which carries campylobacter, the cause of diarrhea.
Campylobacter infections are most often caused by ingesting food that has been contaminated by flies. Climate change and environmental health researcher Budi Haryanto, of the University of Indonesia\'s Research Center for Climate Change (Budi Haryanto Research Center; RCCC-UI), has linked several diseases with climate change.
High rainfall and warmer temperatures had effected an increase in diseases such as diarrheal diseases, leptospirosis, respiratory disorders and diseases transmitted by vectors like mosquitoes.
In the case of leptospirosis, high rainfall caused large pools of stagnant water to form. "The mouse urine that carries the Leptospira bacteria floats in floodwaters. A wounded person can easily become infected with leptospira," said Budi.
Diarrheal diseases are also associated with high rainfall and flooding. Clean water contaminated with bacteria in turn contaminates food as well as eating and drinking utensils. During the dry season, the air is dry and the water supply declines. "As a result of the dry air, dust [is easily carried in the air] and contaminates clean water," he said. (AIK/ISW)