As the southwest monsoon drenches Sri Lanka’s western belt, another less visible storm brews in its wake: the rise of mosquito-borne illnesses. With over 24,000 confirmed dengue cases and an unquantified but growing wave of chikungunya, public health officials are racing against time to prevent a full-blown crisis.
While the situation hasn’t reached epidemic proportions, both diseases are spreading rapidly, fuelled by monsoon rains, urban crowding, and inconsistent community engagement. The nation’s health infrastructure, already grappling with seasonal viral outbreaks and ongoing economic strain, is now navigating a complex battle on multiple fronts.
Dengue in the spotlight
According to National Dengue Control Unit (NDCU) Consultant Community Physician Dr. Preshila Samaraweera, Sri Lanka has recorded 24,180 dengue cases to date in 2025. The Colombo District continues to bear the brunt of the outbreak, followed by Gampaha and Kalutara, with the Western Province collectively accounting for around 45% of total cases.
“We’re seeing a seasonal spike, especially with the onset of the southwest monsoon. There were 5,166 cases in April, which rose to 6,042 in May. This is typical for this time of year,” Dr. Samaraweera explained.
Despite public concern and social media alarm, the Health Ministry maintains that the situation is at a manageable level, being a part of the expected seasonal trend that peaks between May and July, aligning with the pattern of previous years.
A coordinated national effort
To manage the spike, the Ministry of Health has rolled out targeted vector control measures in high-risk areas. A special mosquito control campaign was conducted last week across 95 Medical Officer of Health (MOH) divisions, using data from 2019 to 2024 to identify hotspots.
“These operations include inspections of homes, schools, temples, mosques, churches, construction sites, and other potential mosquito breeding grounds,” said Dr. Samaraweera.
Once a dengue patient is hospitalised, the corresponding MOH division is immediately alerted. Public Health Inspectors (PHIs) and other field staff are then deployed to carry out area-specific interventions, including legal action against non-compliant premises.
Community involvement has been critical. “We have had support from the tri-forces, Samurdhi officers, grama niladharis, and volunteers. It’s a collective fight,” she emphasised.
The ministry, through the Medical Officers of Health, is actively engaged in mosquito control, according to Epidemiology Unit Consultant Epidemiologist Dr. Athula Liyanapathirana.
“This includes regular inspections of breeding sites by PHIs and community volunteers. Legal action is also taken where necessary. Fogging is carried out based on case reports, referred to as case-based fogging. Public education campaigns are ongoing, focusing on eliminating breeding grounds.
“On the treatment side, we are conducting regular training for doctors and nurses, particularly at the National Institute of Infectious Diseases (NIID, formerly known as IDH) and other medical institutions. Thanks to these efforts, Sri Lanka continues to maintain one of the lowest case fatality rates for dengue globally,” he said.
Chikungunya resurgence
While dengue has become an unfortunate fixture in Sri Lanka’s public health calendar, chikungunya has re-entered the national spotlight after a hiatus of more than a decade.
“We are seeing a noticeable rise in chikungunya cases through our sentinel surveillance system,” confirmed Dr. Liyanapathirana. “Although comprehensive data is still being compiled, recent trends show a surge, which is possibly plateauing but is still concerning given the timing of the rains,” he said.
“Both dengue and chikungunya are transmitted by the Aedes mosquito, primarily Aedes aegypti and Aedes albopictus, so any spike in mosquito breeding due to rainfall leads to a spike in both diseases,” he said.
However, unlike dengue, chikungunya is yet to be classified as a notifiable disease in Sri Lanka, which means doctors are not legally required to report cases. This gap in policy is now being bridged.
“We have recently instructed all medical practitioners to report suspected chikungunya cases through the national notification system, because previously it was not identified as a disease that required medical practitioners to notify the authorities,” Dr. Liyanapathirana said.
Is this an epidemic?
Given the numbers and public panic, some media outlets have raised alarms about an epidemic. However, both officials stress that while the situation is serious, it is yet to meet the epidemiological threshold for an official declaration of an epidemic.
“While there is a significant rise in chikungunya, especially in Colombo and Gampaha, we haven’t crossed the thresholds that define an epidemic,” explained Dr. Liyanapathirana. Similarly, Dr. Samaraweera added: “The dengue increase is seasonal and within manageable limits, provided we maintain our current pace of intervention.”
Diagnostic confusion
One of the challenges facing both the public and health practitioners is symptom overlap among various viral infections. In addition to dengue and chikungunya, influenza and other viral fevers are also in circulation, creating diagnostic confusion and often delaying appropriate care.
“This is why early medical attention is crucial,” stressed Dr. Samaraweera. “We urge anyone with fever, muscle aches, headache, vomiting, or fatigue to visit a doctor within two days. A full blood count or NS1 antigen test can help identify dengue. Prompt intervention is key.”
Dr. Liyanapathirana echoed the concern, noting that chikungunya, unlike dengue, often featured intense joint and muscle pain, which could linger for weeks or even months. “It’s crucial not to self-medicate with Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), like ibuprofen. These can be harmful. Instead, patients should use paracetamol as prescribed and stay well hydrated.
“Chikungunya can often be managed at home under medical supervision, but early diagnosis is essential to differentiate it from dengue, which may require hospital care. Blood tests can help with this distinction,” he said.
Treatment protocols and public vigilance
Sri Lanka’s medical system is on alert. According to Dr. Liyanapathirana, the NIID and other medical institutions have ramped up training sessions for doctors and nurses, especially on updated clinical management guidelines for chikungunya.
“The guidelines for acute phase management have already been distributed, and we are finalising the guidelines for the subacute and chronic phases. All of these are accessible via the ministry’s website,” he noted.
Meanwhile, dengue care protocols are being followed across hospitals, according to Dr. Liyanapathirana, and Sri Lanka continues to maintain one of the lowest case fatality rates globally, a testament to its proactive approach and skilled medical workforce.
Both doctors agree that community-led mosquito control is the most effective way to reduce the burden of vector-borne diseases.
“Mosquitoes can fly up to 100 metres, so it’s not enough to clean your house. The entire neighbourhood needs to be vigilant,” said Dr. Liyanapathirana. He recommended weekly clean-up drives, especially around abandoned properties, construction sites, rooftops, and school yards, which are common breeding sites for Aedes mosquitoes.
Simple steps such as covering water containers, disposing of old tyres and plastic containers, cleaning roof gutters, using mosquito nets and repellents, and wearing long-sleeved clothing, especially for children, can go a long way in minimising risk.
Dr. Liyanapathirana cautioned that the measures should especially be enforced during the dawn and dusk hours, when Aedes mosquitos peak in activity.
“Don’t wait for PHIs to show up. If every community takes responsibility, we can significantly reduce both dengue and chikungunya,” Dr. Samaraweera emphasised.
While the Ministry of Health is scaling up data collection and intervention efforts, experts believe that the real battle lies in behavioural change.
“There is a tendency to become complacent once the rain stops or case numbers dip. That’s dangerous. Vector control must be a year-round commitment,” warned Dr. Liyanapathirana.
There is also hope that chikungunya will soon be classified as a notifiable disease, enabling better tracking and faster policy response. Until then, real-time surveillance, rapid diagnostics, and continuous public education remain the most reliable tools in Sri Lanka’s arsenal.