A patient with severe dengue fever is treated at the Hospital for Tropical Diseases in HCM City as cases continue to rise nationwide. — VNA/VNS Photo

HCM CITY — Việt Nam recorded more than 50,000 dengue fever cases in the first five months of this year, a 2.5-fold increase from the same period last year, prompting health experts to warn the mosquito-borne disease is becoming increasingly unpredictable and no longer follows its traditional seasonal pattern.

Speaking at a seminar on dengue fever on Wednesday ahead of ASEAN Dengue Day, Võ Hải Sơn, deputy director of the Ministry of Health's Department of Disease Prevention, said the outbreak had shown unusual trends over the past two years.

"In previous years, dengue cases typically declined toward the end of the year. However, case numbers remained high throughout November and December 2025 and have continued to rise in 2026," he said.

Health experts attributed the increase to prolonged periods of hot and humid weather interspersed with heavy rainfall, creating favourable conditions for mosquitoes to breed.

They also warned that the DENV-2 serotype, which is currently dominant, is associated with a higher risk of severe illness.

The spread of dengue is also expanding beyond traditional hotspots.

According to the World Health Organization (WHO), climate change, rapid urbanisation and shifting weather patterns are enabling the disease to establish itself in areas that previously recorded few or no cases, including several northern provinces.

Global trend

Angela Pratt, WHO Representative in Việt Nam, said the country's experience reflected a broader global trend.

Worldwide dengue infections increased tenfold between 2010 and 2019, but the disease is now considered one of the world's most significant public health threats, according to WHO.

Experts also noted a shift in the age profile of patients. More than a decade ago, children under 15 accounted for 60-70 per cent of dengue cases in southern Việt Nam. Today, infection rates among adults and children are nearly equal.

Assoc. Prof. Dr. Nguyễn Thanh Hùng, vice president of the Vietnam Pediatric Association and director of Children's Hospital 1 in HCM City, said: "This means everyone in a household is now at risk." 

Doctors warned many patients continue to underestimate the disease, delaying medical treatment or stopping follow-up visits once their fever subsides.

However, the most dangerous stage of dengue typically occurs between the third and fifth days of illness, when severe complications such as shock, major bleeding or organ failure may develop.

Severe cases can require intensive care, blood filtration or mechanical ventilation, resulting in treatment costs reaching hundreds of millions of đồng.

Alongside traditional prevention measures such as mosquito control and eliminating standing water where larvae breed, health authorities are exploring new tools to combat the disease.

Pratt said AI-based early warning systems are improving outbreak forecasting, while dengue vaccines could help reduce infection rates and the risk of severe disease.

The Ministry of Health is studying pilot vaccination programmes in selected localities while continuing to strengthen disease surveillance, mosquito-control measures and treatment capacity.

WHO has set a target of eliminating dengue-related deaths by 2030.

Health experts said achieving that goal will require not only stronger public health interventions but also greater public awareness and proactive prevention efforts by communities and households. — VNS