Mapping Mexico’s dengue fever hotspots
Rutgers researcher co-creates tool to help identify outbreaks and prioritize virus control efforts
Peer-Reviewed PublicationAs many as one in five dengue fever deaths in the Americas occur in Mexico, and the rate of the disease’s severity has been increasing for decades, according to the World Health Organization. Now, a Rutgers researcher has generated data that could help curb the mosquito-borne illness in the country.
Ubydul Haque, an assistant professor of global health at the Rutgers Global Health Institute, has analyzed data from Mexico’s Ministry of Health to identify dengue fever hotspots. Working with epidemiologists at the University of North Texas and Universidad Autónoma de Nuevo León, the team calculated environmental and socioeconomic risk factors and mapped areas where severe outbreaks occur.
The findings are published in the journal Ecological Informatics.
“These maps can aid health officials in targeting fogging activities or enhancing surveillance,” Haque said. “By knowing where severe dengue fever frequently occurs, we can significantly reduce the number of cases.”
Dengue fever has been reported in 28 of 32 states in Mexico, and researchers have long known that socioeconomic status and weather affect dengue fever case counts in those states. But the factors contributing to disease severity hasn’t been studied.
Past work also has failed to account for geographic distribution of variants, or serotypes. There are four dengue virus serotypes – DENV-1, DENV-2, DENV-3 and DENV-4 – and transmissibility and lethality differ by each.
To fill these research gaps, Haque analyzed laboratory-confirmed dengue fever infections from 71,059 individuals in 2,469 Mexican municipalities collected between 2012 and 2020. Samples included serotype classification.
This data was overlaid with localized weather and socioeconomic statistics, such as literacy, access to health services, electricity and sanitation.
As expected, each degree Celsius increase in temperature was associated with lower rates of occurrence of the virus – mosquito eggs don’t hatch well in high heat – while increasing humidity was associated with an increase in the rate of each virus serotype.
Moreover, the researchers determined that lower socioeconomic status increases risk of dengue fever, and indicators such as access to education, information and infrastructure are better predictive factors of dengue fever distribution.
From this data, the researchers produced heat maps highlighting dengue virus distribution and severity. Hotspots were generally observed in humid coastal regions at lower altitude. Throughout the country, the most prevalent serotype was DENV-2 and the least prevalent was DENV-4, Haque said.
While efforts are underway to develop DENV-specific vaccines, mosquito control programs such as fogging, and drone surveillance remain the most effective means of slowing the disease’s spread. Haque said data visualization can help health officials plan where to target their activities.
“From our data we know that DENV-2 is deadlier compared to other serotypes,” Haque said. “If regional health officials had limited resources for their control program, they could focus most of their resources in places where DENV-2 was prevalent.”
The WHO estimates dengue fever infects as many as 400 million people every year, killing thousands. With climate change predicted to increase dengue fever cases in Mexico over the coming decades, continuous surveillance of serotype patterns will be essential to preventing or slowing the rate of increase, Haque said.
JOURNAL
Ecological Informatics
METHOD OF RESEARCH
Content analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
The ecological determinants of severe dengue: A Bayesian inferential model
https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue
Dengue and severe dengue - World Health Organization (WHO)
Jan 10, 2022 ... Dengue is a mosquito-borne viral disease that has rapidly spread to all regions of WHO in recent years. Dengue virus is transmitted by female ...
https://en.wikipedia.org/wiki/Dengue_fever
Dengue fever - Wikipedia
Dengue fever virus (DENV) is an RNA virus ; The dengue virus genome ; Dengue virus is primarily transmitted by Aedes mosquitos, particularly A. aegypti. · These ...
Dengue fever, a man-made disease
EXCERPT
SUPERSTITIOUS South-East Asians might suspect a supernatural curse. Reeling from economic turmoil, and bracing themselves for a return of the smog that forest fires last year belched over much of the region, they are also now battling the Aedes aegypti mosquito, and the disease it carries: dengue fever. In most of the tropical world, dengue is ever-present, and spreading. Last year saw the highest-ever recorded number of infected people in the Americas, with Brazil and Cuba especially badly hit. This year dengue has reached pandemic proportions in Indonesia and Thailand, and Malaysia, Cambodia and Vietnam are all experiencing serious outbreaks. Most sufferers are children.
As with the smog, it is tempting, but unfair, to blame mother nature. The weather patterns brought by the El Niño effect have mucked about with the mosquito's life-cycle, just as they have delayed the rains to douse the burning trees. But dengue is a disease of urbanisation and human travel. In the words of Suchitra Nimmannitya, a Thai specialist on the disease, the infected Aedes aegypti is “a man-made mosquito”.
LETTERS
DOI: https://doi.org/10.20529/IJME.2014.050
I faced a serious ethical dilemma while attending a couple of cases of dengue fever at a ward in the Kolkata Municipal Corporation (KMC) area during September 2013. Two patients had tested positive for dengue IgM antibody by MAC ELISA. Adjacent to their house was a vacant plot of around 1500 sq feet and this was heaped with domestic waste from the neighbouring houses. The waste comprised plastic cups, thermocol plates, plastic bags and boxes of biscuits, cakes, chips and other foodstuff, coconut shells, bicycle tyres and earthen pots. These served as a permanent breeding ground for Aedes mosquitoes, the vector for the dengue virus. The owner of the land lived elsewhere and the local people had been dumping their domestic waste here indiscriminately, without the owner’s permission. They had converted the area into an unauthorised garbage dump, despite the fact that the conservancy workers of the KMC visited the place for house collection of wastes every day.
Later, I came to know that two more NS1-reactive dengue cases had been reported from the same locality the following week. I informed the KMC health department about the matter, as dengue is a notifiable disease here. Health workers from the KMC visited the area and discovered several plastic cups, earthen pots, coconut shells and the like, which contained stagnant water. Larval and pupal stages of the Aedes species were found on the rooftops of most houses in the locality. Van-fogging of the area with adulticides was performed, as well as source reduction, followed by chemical (Temephos 50% EC) spraying in the moist areas and other possible breeding sites that could not be destroyed. Last year, there had been a dengue outbreak in the area and three deaths due to dengue shock syndrome were reported. The KMC authorities have been sending surveillance workers with information, education and communication (IEC) materials, such as handbills, to this area on a weekly basis for the past six months. They have even hired an auto-rickshaw and fitted it with a microphone to conduct IEC activities in the area twice a week. Their field workers and surveillance workers have been carrying out anti-larval activities, such as source destruction and chemical spraying, and conducting active surveillance for new cases of fever throughout the year. Further, IEC activities are being carried out through television, FM radio, newspapers, electricity bills, handbills, and so on.
Despite the above measures, people continue to dispose of waste indiscriminately, resulting in the accumulation of stagnant water. Therefore, it was evident that mere IEC and chemical spraying would not suffice; the civic authorities would need to take decisive action to improve the environment.
Despite the outbreak of dengue in the area the previous year, the residents failed to reduce the sources conducive to the breeding of mosquitoes in their own premises. Even after the enormous efforts of the KMC health department, they failed to realise how they themselves had promoted the breeding of Aedes mosquitoes. Should people have the liberty not to keep their premises clean when this can make others ill and even result in their deaths? Should the authorities, in the interest of beneficence and justice for the larger community, have the right to forcibly take action to clean up people’s premises? Should people have the right to convert others’ premises into an unauthorised dumping ground, endangering the life of others in the community? Should the authorities, in the interest of non-maleficence and justice for the owner, as well as beneficence for the community, have the right to take legal action against such transgressions? The dilemma remains unanswered.
About the Authors
Subhasis Bhandari (subhasisbhandari@gmail.com)
General Physician and Health Research Scholar
Bhandari House, 151, Diamond Harbour Road, Behala, Kolkata 700034
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