Why dengue and malaria continue to plague India – and how climate change is making them worse

India is unable to eliminate malaria and dengue because of a lack of testing and diagnosis of these diseases, and because of delayed treatment, experts say. In addition, climate change is making the weather more conducive to mosquitos, the vectors that spread these diseases.

India accounted for about 82% of all malaria deaths and as many cases in South-East Asia in 2020. Reported cases of dengue increased 22%, from 1,57,315 cases in 2019 to 1,93,245 cases in 2021.

Both malaria and dengue are vector-borne diseases, spread by organisms, like mosquitoes, that transport parasites and pathogens from one infected person (or animal) to another. Of all vector-borne diseases in India, the most cases in 2021 were of dengue and malaria, government data shows. These are the latest comparative data available for vector-borne diseases.

India needs to ramp up testing, collect better data on the prevalence of these diseases and decentralise care at the village-level, experts say.

If India is able to eradicate malaria, it will join countries, including Iran and Malaysia, that have not reported a single malaria case for the past three years as of 2020, and China and El Salvador that were declared malaria-free in 2021.

Progress so far

Malaria, transmitted by the infective bite of the Anopheles mosquito, is caused by four types of parasites, two of which, Plasmodium vivax (P.vivax) and Plasmodium falciparum (P.falciparum), infect humans.

P. falciparum causes more severe infection, and can cause cerebral malaria, said Rakhal Gaitonde, professor of public health at the Sree Chitra Tirunal Institute for Medical Sciences and Technology in Thiruvananthapuram. “It’s usually the type of malaria that kills. Vivax usually doesn’t kill unless, of course, the patient is very sick (imuno-compromised).”

In 1953, India’s programme concentrated on spraying the insecticide dichloro-diphenyl-trichloroethane, or DDT, to kill mosquitos. The programme was expanded in 1997 under the Enhanced Malaria Control Project, and in 2003, the government began the National Vector Borne Diseases Control Programme, which includes all vector-borne diseases, including malaria.

Since 2003, malaria cases have declined 91.3%, from 1.02 million cases to 161,516 cases in 2021, and deaths have declined from 1,006 to 90, according to government data.

The government says India’s success in reducing malaria cases is because of controlling the population of mosquitos in high risk areas, early case detection and effective treatment by strengthening referral services and changing patient behaviour by engaging with citizens, according to this reply in the Lok Sabha in November 2021. But experts say more needs to be done to eradicate malaria.

India says it is working towards the World Malaria Day 2021 goal of “Zero Malaria” by 2030.
Under the National Framework for Elimination of Malaria 2016-’30, the government had aimed to have zero indigenous cases and deaths due to malaria by 2022 in 15 low transmission states and Union Territories and in 11 moderate transmission states and Union Territories.

The 26 states reported 11,834 cases by June 2022, as per the National Centre for Vector Borne Diseases Control.

Dengue is a viral disease, transmitted by the Aedes Aegypti mosquito. The disease occurs in two forms: dengue fever, a severe, flu-like illness, and Dengue Haemorrhagic Fever, a more severe form of the disease, which may cause death.

Dengue occurs in waves, data show, with no clear pattern over the years. In 2011, India had 18,059 cases of the disease, while in 2021, it had over 10 times more, at 1,93,245 cases, according to data from the 2011 National Health Profile and from the website of the National Vector Borne Diseases Control Programme.

Underreporting of cases

India’s malaria and dengue data are collected mainly by the Health Management Information System and the Vital Registration System and Medical Certification of Cause of Death. But not all malaria and dengue cases are diagnosed, leading to undercounting.

Also, India does not register about three million deaths and does not certify the cause of death of about eight million people, IndiaSpend reported in August 2021. No certification could mean that some malaria and dengue deaths are also not certified, and thus undercounted.

“There are a lot of overlaps of symptoms between malaria and dengue, and other tropical diseases, and viral fever. In the early phases even swine flu and leptospirosis [have similar symptoms],” which could lead to incorrect diagnosis or reporting of malaria and dengue cases, said Bharat Agarwal, internal medicine specialist at Apollo Hospital in Navi Mumbai.

Dengue cases are also poorly quantified with existing public health surveillance systems, as milder forms of the disease are less likely to be reported, and the system also fails to register cases treated in the private sector, where most patients seek care, according to this 2018 study by researchers from Indian Council of Medical Research.

Some experts believe that the number of dengue deaths are higher due to the fact that they are reported better. Dengue is more prevalent in urban areas, where there are better testing services, while malaria is more common in rural areas, and forest areas with a larger scheduled tribe population, both of which are underserved by health services, said Chandrakant Lahariya, an epidemiologist and public health specialist, who recently co-authored a book on Covid-19.

Another cause for undercounting is that data collection exercises are image-building exercises for governments, said Gaitonde. “If data collection is used for image-building exercises, the tendency is to highlight the positives and downplay or write-over the negatives.”

Take for example, leprosy, he explained. In 2005, the government said that leprosy was eliminated from the country, which meant the government reduced funding and surveillance of the disease.

One of the impacts of this, as per studies in 2009 and 2015, was that India was missing leprosy cases in certain areas, including tribal hamlets. Experts had told IndiaSpend in 2019 that India might be showing lower leprosy cases than there were.

Further, most health workers collect data on cases as a formality, said Gaitonde. For instance, he explained, processed and analysed data are never sent back to health workers who could take decisions on the ground based on those data.

Lack of testing

In 2017, the World Health Organization had estimated that India only reports 8% of its malaria cases to the surveillance system. Today “even if we give a best case scenario, it will not be very different than 12%, 15%”, said Lahariya. “We need to remember that in two years of Covid-19, almost all other non-Covid services had suffered.”

Malaria is tested by blood smear examination, the “gold standard” for detecting the malarial parasite.

Five states performed 64% of the total malaria blood smear tests while states like Chhattisgarh, Jharkhand and Odisha, considered hotspots for malaria, conducted just 4.8% (3,75,891) of the tests until May 2022.

There are two kinds of tests for dengue: direct tests, done through ELISA, to detect the presence of antibodies for dengue and a dengue PCR, which detects the genetic material of the dengue virus.

Some experts also point out that people are not forthcoming with their symptoms, making it harder to diagnose them. There is an inertia in getting tested in those who are affected and suffering from fever, said Ambarish Dutta, an epidemiologist at the Public Health Foundation of India.

Further, India’s surveillance system is not strong enough to pick up all the fever cases and get them tested for dengue during an outbreak, said Dutta. The government’s Integrated Disease Surveillance Programme should be very vigilant whenever there are outbreaks of fever, Dutta added, and there should be more testing.

Dengue has four subtypes and if the population was already exposed to the subtype common in that year, and has developed immunity against it, there will not be a large outbreak, said Gaitonde.

The government has to procure kits fast when cases start rising, as buying in advance would mean kits expire if they aren’t used that season, Lahariya said. Because of this, there is usually a shortage of test kits, experts say. For instance, there have been media reports in 2019 and 2021 from Mohali in Chandigarh and Hyderabad in Telangana of a shortage of dengue testing kits.

Access to treatment

In areas where malaria is endemic – which means a disease is consistently present but limited to a particular region – it is important that people are able to reach out for treatment early. “Even though it won’t be possible to save all patients with the best treatment, we can definitely save a lot more lives,” said Lahariya.

States like Chhattisgarh, Jharkhand, West Bengal, Odisha and the northeastern states have the highest burden of malaria and also have high malnutrition rates, which makes them more likely to have worse outcomes with malaria. In addition, malaria makes children more likely to be undernourished, according to a 2019 paper by the Observer Research Foundation.

There is no known cure for dengue, and cases can be treated at home with regular oral hydration and fever management. However there is danger of bleeding, in which case the patient would need to be hospitalised and need blood transfusions, a 2017 study found. During an outbreak this causes shortage of blood platelets, says the study.

Controlling mosquitoes

Mosquito growth, which has to be reduced to control these diseases, is in part related to climate change and urbanisation. Risk of dengue increases with increasing temperatures and increasing rain in India, found a study published in 2019.

Experts also point out that the change in human habitations has helped mosquito populations spread faster. India’s population density in 1961 was 155 people per square kilometre, which in 2021 increased to 469 people.

The Aedes Aegypti mosquito, the primary vector of dengue, breeds in natural containers such as tree holes and bromeliads, but nowadays it has adapted to urban habitats and breeds mostly in man-made containers, including buckets, mud pots, discarded containers, used tyres, storm water drains etc., making dengue an “insidious disease in densely populated urban centres”, according to this World Health Organization article.

Mosquitoes that are responsible for transmitting malaria in India were found both in urban and rural areas, according to a study published in the The American Journal of Tropical Medicine and Hygiene in 2016.

“What you really need to do is much more in depth in terms of preventing mosquitoes from breeding, preventing mosquitoes from interacting or biting humans,’’ said Gaitonde. “There is a need to look at the social determinants like income, house type, distance to health sub-centre etc. in terms of exposure to these diseases.”

India currently controls the spread of mosquitoes by Indoor Residual Spraying in selected high-risk areas, Long Lasting Insecticidal Nets in high malaria endemic areas, use of larvivorous fish, anti-larval measures in urban areas including bio-larvicides and minor environmental engineering and source reduction for prevention of breeding, according to the National Vector Borne Diseases Control Programme website.

Starting small

There is a need for decentralised planning as both malaria and dengue exist in particular geographies, said Gaitonde. Village-level and ward-level planning, combined with community participation, involving all government departments including public works and education, and not just the health department, could help in both controlling mosquitos and diagnosing and treating the disease, Gaitonde said.

There are several examples of successful village-level care of malaria and dengue from India.

The Tamil Nadu government decided to make the ELISA test for dengue available at primary health centres, rather than at district hospitals. This led to more patients seeking early care, testing positive, more hospitalisation and a reduction in deaths, a 2022 study on the impact of this programme found. Furthermore, as the patients did not need to travel to tertiary health centres, this saved Rs 129 per person.

A study of the 2013 Comprehensive Case Management Project in Odisha for access to diagnosis and treatment and improved surveillance on malaria transmission, found that the number of underserved villages and hamlets decreased by 89%, and ASHA-plus providers tested half of all fever cases for malaria, and diagnosed and treated 55% of malaria cases at the level of the village itself in 2015.

The programme included training and supervision of health workers, ensured no stock-outs of malaria tests and drugs, analysed verified surveillance data and appointed alternative providers to underserved areas, the study said.

This article first appeared on IndiaSpend, a data-driven and public-interest journalism non-profit.