Dengue continues to top Tamil Nadu’s list of deadliest vector-borne diseases

CHENNAI: Looking back at the year, tackling vector-borne diseases has stood as the most challenging task for the State Health Department. Dengue, Chikungunya, Leptospirosis, Scrub Typhus and Encephalitis saw a surge compared to last year, compelling the department to amplify prevention and control measures.

Dengue concerns remain high

Dengue remains the most concerning vector-borne disease prevalent in Tamil Nadu, as the cases tally reached 26,740, the highest in 15 years. It caused 13 deaths so far.

The disease was an exacting task in neighbouring states Kerala and Karnataka as well, where the tally climbed upwards of 71,000 and 35,000. It claimed 129 lives in Kerala.

In the countrywide ranking on number of dengue cases by the National Vector Borne Diseases Control Programme and the State Health Department, Tamil Nadu took the third spot increasing concerns.

While mortality remains low, TN recorded five dengue-related deaths in the last two months. The highest number of cases was reported in September, when 4,347 people were infected.

The last major surge in dengue was in 2017 when it recorded 63 deaths and 23,035 cases.

As rains continue across the State, the need to increase vigil on the disease stands as a priority.

Leptospirosis - an emerging challenge

Leptospirosis, the bacterial disease that spreads through the urine of infected animals like dogs and farm animals, saw an unexpected rise and saw a total of 3,526 cases in Tamil Nadu this year.

The need to spread more awareness is vital as the case numbers are expected to surge in the coming years.

The Directorate of Public Health (DPH) did an analytical study to predict the Leptospirosis cases until 2027 in Tamil Nadu and used the data from the Integrated Disease Surveillance Programme - Integrated Health Information Platform portal of leptospirosis cases reported in TN from January 2021 to March 2024.

The analysis showed that out of 73,329 people, 7,080 had leptospirosis, taking the test positivity rate to nearly 10 per cent. In 2023, 2,799 cases were reported, 2,643 in 2022. The active surge in leptospirosis cases started in 2021, when it had reported less than 1,600 cases.

The analysis published in the Tamil Nadu Public Health Journal stated that the statistical model’s predictions on the number of cases between January 2021 and March 2024 matched the numbers reported in TN as per IDSP-IHIP data and it was used to forecast numbers for the next four years.

The study noted a steady increase in cases each year, and the prediction was about 3,474 in 2024, 3,677 in 2025, 4,986 in 2026, and 5,785 in 2027.

“The increased surveillance is being done for early diagnosis and providing the right treatment to those affected,” stated the study.

It is significant to note that leptospirosis requires hospitalisation in about 60 per cent of cases, and the associated morbidity can be severe and can lead to multi-organ failure and death in some cases.

Chikungunya triples its victims in 2024

Another mosquito-transmitted threat that steadily posed a danger was Chikungunya. In 2023, the chikungunya cases tally was only 222. However, in 2024, it reached a whopping 603. The positive dip resulted from the low reporting in the pandemic years. In 2020, the number of cases had decreased to 224 compared to 2019’s 623 tally. It saw an even lesser number in 2021 when only 153 cases were reported.

The rise in dengue cases in Tamil Nadu has indicated more breeding grounds for mosquitoes, and while Aedes mosquito leads to the dengue virus, it has also led to a rise in Chikungunya cases.

Scrub Typhus records zero mortality

The cases of Scrub Typhus have stood at 6,343 this year, but the mortality remains zero. However, the state health department officials say that there needs to be strict monitoring of cases to provide medical care at an early stage.

Malaria and JE record a dip

Malaria cases, on the other hand, have seen a dip as only 341 cases have been recorded in Tamil Nadu this year. The numbers have seen a downward trend in the last five years, from 891 cases in 2020 to 772 in 2021, 351 in 2022 and a slight surge to 384 in 2023.

The mortality due to malaria has remained zero in the last five years. However, Chennai records the highest number of malaria cases, accounting for about 120 cases. The data indicates that the number of cases in urban areas is significantly higher than in rural areas. At least 11 health unit districts reported zero cases of malaria (until August).

The tally for Japanese Encephalitis is 39 in Tamil Nadu this year, and it poses a lower risk than other vector-borne diseases in the State.

What DPH has to say

The Directorate of Public Health and Preventive Medicine says that the number of vector-borne diseases has been high because of daily reporting of dengue cases and tracking of other diseases. The state health department also instructed the private hospitals to report dengue cases.

“The Directorate of Public Health and Preventive Medicine is tracking all the cases of dengue being brought to the hospitals, including private hospitals in Tamil Nadu. The testing has also been increased. The increased number of cases is due to our increased surveillance. We included many private institutions and ensured every institution reported their daily numbers. That is why, even with the increase in cases, we don’t have high mortality,” said Dr TS Selvavinayagam, Director of Public Health and Preventive Medicine.