Experts suggest that the populace venturing outdoors and an extended rainy season contributed to the elevated viral infections across India.
Aedes mosquitoes, responsible for dengue transmission, are known for their aggressive day-biting behaviour and the ability to survive indoors for an extended period. (Shutterstock)
With the decline of Covid cases in India, the year 2023 bore witness to a surge in cases of seasonal flu. Tamil Nadu experienced a notable increase in seasonal influenza, while Kerala recorded a higher incidence of related fatalities.
Among the southern states, Karnataka and Kerala reported a substantial rise in dengue cases, with Kerala witnessing the highest number of deaths attributed to the dengue virus.
Experts posit that the populace venturing outdoors and an extended rainy season, owing to a delayed onset of winter and early summer, contributed to the elevated viral infections across the country.
According to the Central Surveillance Unit of the Integrated Disease Surveillance Programme at the National Centre for Disease Control (NCDC), there has been a significant rise in both cases and fatalities linked to seasonal influenza A (H1N1) in the southern states of India in 2023.
Comparing the data from 2022 to 2023, Kerala and Tamil Nadu exhibited substantial increases. Kerala’s cases surged from 90 to 1,025, with deaths rising from 7 to 57. In Tamil Nadu, cases increased from 2,827 to 3,544, the highest in the country, while deaths decreased from 25 to 19. On the contrary, Andhra Pradesh reported 103 cases with no fatalities in 2023, whereas there were only 22 cases in 2022.
Karnataka witnessed a decrease in cases, reporting 118 cases in 2023 compared to 517 in 2022, with no deaths reported in 2023. Telangana also observed a decline in both cases and deaths during the same period, with 116 cases in 2023 compared to 343 cases in 2022. Both years, the state did not report any deaths.
“The increased number of people opting for testing is a big factor contributing to the elevated case count in the states. The fluctuating temperatures and inadequate drainage systems create an environment conducive to the spread of diseases. Patients with such illnesses often exhibit symptoms like high fever, altered mental states, breathing difficulties, and gastrointestinal issues — all stemming from viral infections,” Dr Karthik Vedula, Consultant Infectious Disease Physician at Yashoda Hospital in Hyderabad told South First.
He added that furthermore, the rapid shift in weather from cold to warmer temperatures leads to an increase in other seasonal infections.
“As winter transitions to summer, there is a notable surge in patients reporting viral fever, cold and cough, and severe throat infections. The significant impact of weather on overall health is evident throughout this transition,” said Dr Vedula.
The cumulative data for seasonal influenza A (H1N1) in India from 2018 to 2023 shows a fluctuating trend. In 2018, the country reported 15,266 cases and 1,128 deaths, in 2019 there were 28,798 cases and 1,218 deaths, in 2020 there were 2,752 cases and 44 deaths, in 2021 there were 778 cases and 12 deaths, and in 2022 there were 13,202 cases and 410 deaths. In 2023, the country reported 8,097 cases and 129 deaths.
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This data highlights a variable pattern in H1N1 prevalence over the years, with a noticeable decrease in both cases and deaths in 2023 compared to the preceding year. Authorities continue to utilise this information to shape public health strategies and interventions.
A recent study published in the Journal of the American Medical Association (JAMA) stated that the upswing in cases was attributed to diminished immunity among individuals and a reduction in flu vaccination rates.
“Influenza virus infections declined globally during the Covid-19 pandemic. Loss of natural immunity from lower rates of influenza infection and documented antigenic changes in circulating viruses may have resulted in increased susceptibility to influenza virus infection during the 2021-2022 influenza season,” the report stated.
The influenza A (H1N1) pdm09, A(H3N2), and influenza B viruses occurred in a number of nations, as per WHO.
In India, the annual influenza vaccines, commonly known as flu shots, have not gained widespread popularity, despite the recommended practice of taking them every year.
The South Indian states have witnessed a significant rise in dengue cases, marking a concerning situation in the region. Kerala reported the highest number of deaths due to dengue in South India in 2023, followed by Tamil Nadu and Karnataka.
In 2023, Karnataka reported 14,227 cases and 9 deaths, Kerala reported 14,189 cases and 51 deaths, while Tamil Nadu reported 7,133 cases and 10 deaths, Andhra Pradesh reported 5,936 cases and zero deaths, and Telangana reported 7,894 cases and one death due to dengue.
Comparing the figures from 2022, there is a noticeable escalation in dengue cases across the South Indian states. In 2022, Karnataka, Kerala, and Tamil Nadu reported lower numbers, with Karnataka recording 9,889 cases, Kerala 4,432 cases, and Tamil Nadu 6,039 cases.
Dr Rajeev Jayadevan, a member of the Public Health Advisory Panel at the Indian Medical Association, said that the surge in cases is influenced by geographical and climatic factors.
“Kerala, with its abundant water bodies and low-lying wetlands, provides suitable breeding grounds for mosquitoes. The copious rainfall, especially in the latter part of 2023, creates ideal conditions for Aedes mosquitoes, which lay eggs in freshwater, to thrive. The high population density in the region facilitates the easier spread of the virus by mosquitoes,” he told South First.
Aedes mosquitoes, responsible for dengue transmission, are known for their aggressive day-biting behaviour and the ability to survive indoors for an extended period. These mosquitoes can transmit the disease among individuals sharing the same space, whether it’s a residence or workplace.
“Given Kerala’s relatively high population density, there is an increased risk of mosquito-borne virus transmission. Poorly planned urban development can further contribute to a rise in the mosquito population. Individuals residing or working in densely populated areas are more susceptible to infection. The mortality rate is directly proportional to the number of reported cases. Generally, dengue itself is not fatal, but fatalities may occur during a second infection with a different serotype or among individuals with pre-existing health conditions,” explained Dr Jayadevan.
Speaking about cases in Karnataka, Dr Jayadevan said that unusually, the winter season is not typically conducive to mosquito breeding. However, the occurrence of intermittent rains in November, coupled with a delay in the onset of winter conditions, may have contributed to an uptick in dengue cases in 2023.
The total number of dengue cases in India reached 2,34,427, with 274 reported deaths in 2023. Authorities are closely monitoring the situation and implementing necessary measures to address the growing concern.
Hepatitis B cases in South Indian states between July 2018 and September 2023 unfolded as follows: In Andhra Pradesh, 2,544 patients tested positive for Hepatitis B. Karnataka reported 1,631 confirmed cases, while Kerala documented 1,161 cases. Tamil Nadu registered 4,670 confirmed cases, and Telangana recorded 845 individuals with Hepatitis B.
For Hepatitis C cases during the same period, Andhra Pradesh conducted screenings on 5,432 patients, confirming 2,544 cases. Karnataka screened 2,088 individuals, with 1,631 confirmed cases. Kerala screened 2,547 individuals, confirming 1,161 cases. In Tamil Nadu, screenings of 18,350 patients resulted in 4,670 confirmed cases, while Telangana screened 1,402 individuals, with 845 confirmed cases of Hepatitis C.
The total number of patients confirmed positive for Hepatitis B in India during this period reached 452,540, while for Hepatitis C, the total number screened was 386,385, with 204,059 confirmed cases. Punjab emerged with the highest number of patients confirmed positive for both Hepatitis B (69,685) and Hepatitis C (69,685).
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