DDC says Thailand’s top Covid variants show no signs of greater severity

Thailand’s Department of Disease Control has sought to reassure the public that the country’s three most commonly detected Covid-19 variants are not showing signs of causing more severe illness or a higher risk of death, even as seasonal infections continue to rise.

Dr Montien Kanasawat, Director-General of the Department of Disease Control under the Ministry of Public Health, said on Wednesday (June 3) that health authorities had been continuously monitoring the Covid-19 situation and changes in SARS-CoV-2 variants through the Digital Disease Surveillance system, event-based surveillance and laboratory testing.

NB.1.8.1 remains dominant in Thailand

Variant surveillance data from the Department of Medical Sciences between January 1, 2025 and April 23, 2026 showed that NB.1.8.1 was the most commonly detected variant in Thailand, accounting for 50.95% of samples.

It was followed by JN.1, at 24.97%, and XEC, at 9.14%. NB.1.8.1 has been detected and has continued to circulate in Thailand since mid-2025.

Dr Montien said current epidemiological and clinical data had found no evidence that NB.1.8.1 causes more severe symptoms or increases the risk of death compared with earlier variants, although it carries mutations that may improve transmissibility and immune escape.

Most patients continue to experience symptoms similar to other respiratory infections, including fever, cough, sore throat and runny nose.

Cases rise seasonally but remain below five-year median

Data from the Digital Disease Surveillance system as of June 2 recorded 4,156 Covid-19 cases and one death.

The highest number of cases was found among people aged 30–39, followed by those aged 60 and above, and people aged 20–29.

Although Covid-19 cases had increased over the past month in line with seasonal patterns, the number of patients remained below the five-year median, according to the department.

No signal of wider outbreak or increased severity

Dr Direk Khampaen, Deputy Director-General of the Department of Disease Control, said current surveillance data had not detected signs of a widespread outbreak or any increase in disease severity beyond patterns seen in previous seasonal periods.

However, he said Covid-19 remained a respiratory infection that could be found throughout the year, particularly during the rainy season, when people are more likely to gather in enclosed areas.

Surveillance continues through 26 hospitals

Thailand continues to monitor respiratory infections and pathogen changes through a network of 26 sentinel hospitals nationwide.

The system covers major respiratory diseases, including Covid-19, influenza and other viral respiratory infections. Samples from patients who meet surveillance criteria are analysed systematically, and any unusual signals are sent for further testing by the Department of Medical Sciences to identify variants and assess risks in greater detail.

Dr Montien said Thailand’s surveillance system remained in continuous operation to track patient numbers, monitor cluster outbreaks and detect changes in viral variants, allowing authorities to assess the situation and respond to public health risks promptly.

Public urged to keep up basic precautions

The Department of Disease Control advised people to maintain good personal hygiene, wash their hands frequently, wear a face mask in crowded places or when experiencing respiratory symptoms, and avoid close contact with sick people.

People with fever, cough, sore throat or runny nose are advised to take an initial screening test and avoid close contact with high-risk Group 608 individuals, including older people, those with underlying illnesses and pregnant women, to reduce the risk of spreading the virus to people vulnerable to severe illness.