Flooding can create conditions favourable for mosquito breeding, particularly the Aedes mosquitoes responsible for transmitting the dengue virus.
Credit: iStock photo
Mapping flooded areas and stormwater drain networks using Geographic Information Systems (GIS) and remote sensing technology can assist in preventing vector-borne diseases such as dengue and malaria, which surge during the monsoon every year, say experts.
Flooding can create conditions favourable for mosquito breeding, particularly the Aedes mosquitoes responsible for transmitting the dengue virus.
While authorities increase measures to control disease spread during the monsoon, experts believe a robust model identifying potential hotspots can enable timely intervention and reduce dengue transmission risks in flood-prone areas.
'Periodic observation of flooded areas and stormwater drains using remote sensing and GIS could help trace vulnerable population hotspots prone to vector-borne diseases during the monsoon and requiring intervention,' said Murali Krishna Iyyanki, geospatial expert and former director of research and development at Hyderabad's Jawaharlal Nehru Technological University.
GIS is a computer system for capturing and storing data related to positions on Earth's surface while remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance typically from satellite or aircraft.
Advanced technologies like remote sensing and GIS can be employed to periodically monitor flooded areas and stormwater drains. Studies show these technologies significantly improve real-time flood mapping capabilities.
Iyyanki, who has worked on key geospatial projects with ISRO’s National Remote Sensing Centre and the DRDO, noted that high-resolution satellite imagery and aerial photographs from aircraft or drones can provide detailed images of flooded areas.
“By utilising GIS, these images can be overlaid with various data layers, including topography, land use, and infrastructure, to assess flood impact,” he explained.
This year, heavy monsoon rains, coupled with untimely showers, led to a surge in dengue cases in several metropolitan cities across the country.
According to data from the Directorate of Public Health (DPH) and Preventive Medicine, Tamil Nadu has reported a total of 4,048 dengue cases so far this year. In a span of seven days – September 7 to 13 – the state reported a total of 113 dengue cases.
According to official figures, three persons have died in West Bengal so far due to dengue. Around 2,000 people have dengue in the state at present, Chief Secretary HK Dwivedi said on Tuesday.
In Mumbai, 756 confirmed cases of malaria and 703 cases of dengue were reported within the first two weeks of September, data released by the Brihanmumbai Municipal Corporation on September 19 showed.
In Bengaluru, where dengue cases exceeded 4,000, a disease surveillance dashboard and mobile application named PRISM-H (Platform For Research, Integrated Surveillance and Management of Health) were launched by Karnataka government's Department of Health and Family Welfare and the Bruhat Bengaluru Mahanagara Palike. This was in partnership with ARTPARK (AI & Robotics Technology Park) at the Indian Institute of Science (IISc) to develop predictive analytics that could assist public health officials in preparing for dengue outbreaks.
'PRISM-H collates area-wise dengue data over a decade, along with data related to factors like rainfall, humidity, topography, and vegetation, to predict possible dengue hotspots using a GIS-based AI-driven model,” explained Bhaskar Rajakumar, director (healthcare) ARTPARK-IISC.
PRISM-H offers predictive analysis of communicable diseases at least four weeks in advance and monitors the vitals of health workers, disease spread, and test reports, as stated by the Karnataka health department.
Rajakumar said ARTPARK-IISC is working on similar projects like the PRISM-H for other cities with Pune Knowledge Cluster, Gujarat Biotechnology Research Centre and Delhi Research Implementation and Innovation.
While flowing water itself is not directly linked to vector-borne diseases, any flood-affected region can serve as a breeding ground for vectors if residents and authorities fail to take appropriate measures to clear stagnant water, according to Iyyanki.
Dengue cases spiked in some parts of Delhi, which experienced massive floods earlier this year. The national capital also witnessed high level of rainfall in September besides pre-monsoon rainfall, leading to a rise in the number of dengue patients at leading hospitals.
An estimated 3,013 cases of dengue and one death due to the vector-borne disease have been recorded in the city in the past six months, according to official data shared by the Municipal Corporation of Delhi (MCD) in the House on September 26. The MCD also said the number of cases recorded in September was the “highest” in the last four years.
As of August 5, Delhi had reported 19 positive cases of DENV-2, a severe dengue strain, the last MCD report showed.
Delhi also recorded 85 malaria cases from January 1 to August 5.
This year, MCD staff inspected more than 2.95 crore households as part of a campaign to combat vector-borne diseases in Delhi and the authorities issued penalties amounting a cumulative Rs 73 lakh for violations, the civic body said on Monday. During the drive, 83 were found to be mosquito-breeding sites.
A senior MCD official, who didn’t want to be named, stated, 'While the Yamuna floodplains posed minimal concern due to low habitation and natural larval predators, measures like fogging, anti-larval spraying, and local surveillance were implemented in low-lying areas and dengue hotspots to control disease spread.' However, experts suggest that a robust GIS-based model for hotspot identification could be more effective in planning and enhancing disease prevention.
To achieve this, creating a comprehensive map identifying flooded areas and stormwater drains is crucial.
Prerak Shah, technology analyst at Precision Health, a health equity-driven surveillance platform for early warning, said, 'In rural areas, satellite data for flooded areas should suffice, whereas urban flood maps should consider both flooded areas and stormwater drains.' Experts also argue that both event-based and wastewater surveillance are vital for tracking areas susceptible to vector-borne diseases.
'Event-based surveillance mines real-time, location-specific data from the internet, serving as an early warning system for public health authorities,” said Aditya Pangaria, data science research associate at Precision Health.
Experts also stress the importance of participatory surveillance, involving communities in reporting disease-related symptoms to empower vulnerable communities to participate in disease surveillance, early outbreak detection, and reducing disease transmission.
'While remote sensing and GIS provide valuable information, on-ground data mapping with community engagement should go hand-in-hand for optimal results,” Iyyanki added.
Raj Bhagat Palanichamy, senior programme manager, Geo Analytics for Sustainable Cities & Transport programme at World Resources Institute (WRI) India, suggested categorising disease counts by area and age population to identify vulnerable hotspots and prioritise preventive measures such as vaccination drives and awareness campaigns.
Scientific studies of floods and practical analyses of flood impacts on the ground are essential to address the root problem, Palanichamy added.
Experts propose starting preparations for the monsoon season in April or May, as planning ahead could help avoid the yearly high caseloads of dengue and malaria.