Dengue's record year — 2023 brought more cases than the previous 23 years combined

Introduction

Bangladesh’s first officially recorded dengue outbreak, in 2000, hospitalised 5,551 people and killed 93.¹ For the next two decades the disease returned most years, mainly to Dhaka during the monsoon.

Then it exploded. In 2023, the Directorate General of Health Services (DGHS) recorded 321,179 hospitalised dengue patients and 1,705 deaths — by far the worst year in the country’s history.²

321,179

Dengue hospitalisations in 2023 alone — more than the 242,919 recorded in all 23 years from 2000 to 2022 combined.

A disease that keeps setting records

The pattern over the past seven years is one of boom and bust, with each boom larger than the last. The 2019 outbreak, with 101,354 hospitalised cases, was then the largest ever. Cases collapsed in 2020, when COVID-19 restrictions changed people’s movements and health-seeking behaviour, then climbed again to 62,382 in 2022 before the 2023 surge.² In 2024 cases fell back to 101,214 — still the third-highest year on record.³

Between 2000 and 2022 Bangladesh recorded 242,919 dengue cases and 837 deaths in total.⁴ The 2023 outbreak exceeded both figures in a single year.

Deaths have risen even faster than cases

Deaths have grown faster than infections. In 2019, 179 of 101,354 patients died (a case fatality rate of about 0.18%). In 2023 the rate was about 0.53%, and in 2024 about 0.57%.²³

Several factors are thought to be behind this. The dominant virus serotype shifted: DENV-3 had been the main circulating type since 2019, while DENV-2 became dominant in 2023.⁵ A second infection with a different serotype carries a higher risk of severe dengue — and after years of repeated outbreaks, many more people now carry immunity to one serotype but not others.

The World Health Organization found that in the first months of the 2023 outbreak, the case fatality rate among women (0.72%) was more than double that among men (0.32%), and was highest among people over 60.⁵ Late hospital admission, when patients arrive already in shock, is a major driver of deaths.

No longer just a Dhaka problem

Dengue used to be a disease of the capital. In 2023 cases were reported from all 64 districts.⁵ Dhaka still carried the heaviest burden — Dhaka’s city corporations accounted for 52.8% of cases and 78.9% of deaths up to early August — but large outbreaks took hold in Chattogram, Barishal and elsewhere.⁵

The Aedes aegypti mosquito that carries dengue breeds in small pools of clean standing water: construction sites, discarded tyres, flower pots, rooftop tanks. Rapid, unplanned urbanisation and longer, warmer, wetter seasons give it more places and more time to breed, and transmission now continues well beyond the monsoon months.

What would reduce the toll

• Year-round vector control, focused on breeding sites, rather than seasonal fogging campaigns after outbreaks begin.
• Early testing and triage in district and upazila hospitals so patients are treated before they develop severe dengue — most deaths are preventable with timely fluid management.
• Better surveillance that includes private clinics and outpatients, since official counts mainly capture hospital admissions and understate the true number of infections.
• Preparing for vaccines: dengue vaccines are now in use in several countries, and a single-dose candidate (TV005) has been tested in Bangladesh by icddr,b.