Stung by Aedes

Changes in rainfall patterns, long spell of warmer temperatures and rise in the humidity level have allowed mosquito vectors to thrive at locations hitherto less known for an outbreak of dengue and chikungunya. Unplanned construction projects, stagnation of water and dumping of discarded objects have also made the environment conducive for the spread of dengue and chikungunya.

As states grapple with the challenge of a spike in the number of patients, here is a brief rundown on the extent of damage caused by these vector-borne diseases.

 

Dengue cases have spiralled in three states—Karnataka, Kerala, and West Bengal—with Delhi witnessing a sudden spurt in the month of August. The national capital has reported 487 cases of dengue till August 29, with 368 of them being recorded in August alone. In West Bengal, 5,639 people were infected by dengue till August 25 and death toll has reached 23. According to Health Secretary C K Mishra, West Bengal is witnessing a spike in dengue-related deaths because the state has more of Type 3 dengue, while places like Delhi are witnessing Type 2 dengue—a comparatively less virulent strain.

The official data released by the Directorate of Health Services of Kerala shows 279 confirmed cases of dengue between August 20 and 29. Dengue cases have seen a sharp rise in Telangana as well, with more than 175 cases being recorded in Ranga Reddy district (formerly Hyderabad district) till August 14, 2016.

 As on August 29, Tamil Nadu has seen over 1,200 dengue cases and five deaths. The state has shown some progress in tackling the spread by identifying breeding sources and running health camps.

Ever since the first dengue patient in Dehradun was reported on July 13, the number has touched close to 500 within 45 days. According to departmental data, 497 people have been found positive for the disease till August 28. The health experts are intrigued by a rapid increase in dengue cases within such a short span of time.

 While the total number of dengue cases in Uttar Pradesh stands at 336, this is the report from just four out of 36 laboratories designated by the state health department to conduct dengue testing. The actual figure could be much higher.

 Assam witnesses more cases of Type 1 dengue Assam, which witnessed 1076 dengue cases in 2015, has reported close to 458 positive cases this year (till August 18). The Kamrup district has witnessed the highest number of dengue cases in the state, with over 378 positive cases and one death. 

However, most of the cases showed the Type 1 strain of dengue.  Other northeastern states, expect Mizoram, which reported one confirmed case of dengue on August 21, are not yet in the grip of these vector-borne diseases.

While southern states of India are known as traditional hotbeds for Chikungunya virus, the disease has spread its tentacles to other parts of the country, especially Assam, Bihar, Delhi, and Uttar Pradesh.

Between August 20 and 27, 412 cases of chikungunya were recorded in Delhi, taking this year’s tally to 432 so far. In comparison, only 20 cases were recorded from January 1 till August 20. This spurt is attributed to city’s “non-immune population”. People in Delhi have become more susceptible since Chikungunya virus had not been in wide circulation in the city previously.  According to health experts, Chikungunya cases have been on the rise in the national capital but the instances remain under-reported due to lack of testing facilities and the high cost of diagnosis.

 Out of 333 confirmed cases of chikungunya in Maharashtra, Pune alone has approximately 289. This is far higher than 66 cases reported cases in 2015. The number of blood samples received has doubled since last year, and the number of positive cases has increased by more than 400 percent.

 Cases of Chikungunya reported in Gurgaon and Hyderabad

Six cases of chikungunya, the first time in the season, were reported in Hyderabad on August 30 by the state-run Fever Hospital.  In Gurgaon, private hospitals are reportedly getting over 50 cases of every day. The first official case of chikungunya in Gurgaon was confirmed on August 28 when a 35-year-old man from Bihar was tested positive.

 

 A change of climate over time due to natural or man-made causes is increasingly playing an important role in spreading the extent of vector-borne diseases (VBDs).

 According to the World Health Organization, one of the major consequences of climate change is the rise in the number of VBDs, besides heat strokes and skin diseases.

 The development of mosquitoes and pathogens in their bodies is affected by climatic conditions, experts say. Ramesh Dhiman of the National Institute of Malaria Research told Down To Earth that temperature is essential for the development of malarial parasites. “Insects are cold-blooded. Temperature affects the development of vectors or pathogens,” he said.

 In India, Jharkhand and Chhattisgarh are already suitable places for the transmission of vector-borne diseases. But the worrying thing is that in colder areas such as the Himalayan region, projected temperature rise can trigger the breeding of mosquitoes and the rate of transmission. Places like Jammu and Kashmir and Uttarakhand will have to deal with vector-borne diseases, according to Dhiman.

 As dengue is the most deadly of all VBDs (others being malaria, filaria, Japanese encephalitis, chikungunya), Dhiman added that preventing water storage and community participation were vital to prevent outbreaks. The major cause of dengue is water storage in all types of containers. As it is not possible for the government alone to ensure that water does not stagnate, the participation of people becomes important here, he said.

 The epidemiology of dengue in India has changed over the years in terms of strains, geographical location, and severity. Along with temperature rise, rainfall, relative humidity and wind velocity also play an important role in the development of parasites in insects.

 According to Asish Ghosh, the director of Centre for Environment & Development, increasing cases of VBDs can be regarded as the indirect health effects of temperature variations. Temperature rise can lead to floods, especially in the coastal areas and this may, indirectly, lead to an increase in VBDs. Stagnant water serves as breeding grounds for mosquitoes, and thereby, increases the chance of dengue and malaria.

 Ghosh said that all tropical diseases, especially malaria, are prevalent in the southern hemisphere. Mosquitoes breed faster due to high temperature and moisture level. Several studies have shown the higher rate of breeding and outbreak of VBDs occurs in hot and humid conditions.  

 “By 2030-50, India will witness a high level of malarial outbreak and will become the malaria capital of the world,” Ghosh added. The mosquito parasite is already present in the country and further temperature rise will make the situation worse.

 Ghosh emphasised on adaptation measures, especially in coastal areas, to cope up with the situation. According to him, coastal areas should be equipped with vector-borne disease control programmes. People should be encouraged to use mosquito nets. Water should be purified to prevent contamination.

 In India, VBDs are also prevalent due to poor sanitary conditions, Ghosh said. Water-logging and open defecation make matters worse in the country, the expert added.