Karachi: Pakistan’s dengue burden may be more than 125 times the official count, with an estimated 3.28 million cases in 2022 against only 25,932 reported cases, an Aga Khan University-led study has revealed.
The findings indicate that official surveillance may be missing millions of infections while dengue spreads beyond its traditional post-monsoon season to become a year-round public health threat.
Annual dengue cases were estimated to have risen nearly 33-fold from about 100,000 in 2012 to 3.28 million in 2022, with the steepest increase recorded during the final years of the study period.
Sindh emerged as the country’s worst-affected province, accounting for an estimated 2.63 million cases, or about four-fifths of Pakistan’s total burden, in 2022. Its incidence rate reached 45.63 cases per 1,000 people.
Adults aged 15 to 49 were the most affected group, with an estimated 1.6 million cases and an incidence rate of 56 per 1,000 people in 2022.
Laboratory data also showed a higher proportion of dengue cases among men than women across all age groups, although researchers said differences in healthcare-seeking behaviour could partly explain the disparity.
The study found that cases continued to peak during the post-monsoon months of September, October and November, with major surges recorded in 2019, 2021 and 2022.
However, infections were also consistently detected outside the peak season, indicating sustained year-round transmission and progressively larger outbreaks.
“Dengue is no longer just a seasonal threat,” said lead author Dr Zarmeen Nasim, an assistant professor and researcher at the AKU Health Data Science Centre.
“Although cases continue to surge during the post-monsoon months, the data shows signs of sustained year-round transmission, with progressively larger outbreaks over time,” she added.
At the district level, the published paper ranked Tharparkar as having the highest estimated incidence in 2022 at 761.9 cases per 1,000 people, followed by Karachi East at 200.41 cases per 1,000.
Balochistan recorded the lowest provincial estimate, with 6,785 cases and an incidence rate of 0.44 per 1,000 people. Researchers cautioned that lower figures in some regions could reflect limited access to diagnostic laboratories rather than lower disease transmission.
Published in the peer-reviewed journal PLOS ONE, the study analysed laboratory-confirmed dengue cases recorded between January 2012 and December 2022 across all four provinces, Islamabad and 86 districts.
Researchers used de-identified records from three nationwide diagnostic laboratory networks operating more than 990 collection units. A patient was considered positive if either an NS1 antigen or IgM test detected dengue infection.
“The unique feature of this study is its innovative use of routinely collected clinical laboratory data from three nationwide diagnostic laboratory networks to estimate the incidence of dengue fever in Pakistan,” said Professor Erum Khan, Chair of Pathology and Laboratory Medicine at AKU.
The researchers adjusted the laboratory figures to account for people with fever who seek medical care, undergo blood testing and use the participating laboratories, producing estimates intended to represent the wider population.
They acknowledged that the estimates depended on assumptions about healthcare-seeking and laboratory use. Collection centres were also concentrated mainly in Sindh and Punjab, while coverage remained limited in Balochistan, Khyber Pakhtunkhwa, Islamabad, Gilgit-Baltistan and Azad Jammu and Kashmir.
The study called for stronger nationwide surveillance, targeted action in high-burden districts, regular monitoring of mosquito populations, elimination of breeding sites, improved drainage and waste management and better coordination between health and municipal authorities.
Researchers also urged policymakers to consider dengue vaccination alongside existing control measures, while AKU called for exploring Wolbachia-based mosquito control and improving public awareness and the training of healthcare professionals.