Flu cases not expected to surpass last year’s numbers, virologist says
Leading virologist Dr Yong Poovorawan explains how the easing of Covid restrictions combined with prolonged cold weather have contributed to the current outbreak
Amidst concerns about the ever-increasing cases of flu in the country, a Facebook post uploaded today (February 19) by Dr Yong Poovorawan of the Centre of Excellence in Clinical Virology at Chulalongkorn University’s Faculty of Medicine explains the reasons behind this year’s severe outbreak and what people should know.
Dr Yong started by noting that influenza outbreaks in Thailand typically peak during the rainy season or the start of the school year when students – efficient spreaders of the virus – gather in large numbers. However, the current early outbreak this year is more severe than expected.
He explained that during the Covid-19 pandemic, strict respiratory disease prevention measures led to a drastic reduction in flu cases, with no recorded deaths. Since the majority of the population didn’t contract the virus during this period, they lacked natural immunity. As restrictions eased and life returned to normal, a phenomenon known as “immunity debt” emerged. This resulted in many individuals being highly susceptible to infection, causing a sharp rise in flu cases. From last year to early this year, cases have increased by more than 660,000. However, Dr Yong believes that once this “debt” is cleared, the situation will stabilise.
Another contributing factor is the weather. While Thailand traditionally lacks a distinct winter, this year has seen prolonged cold temperatures, particularly in the northern and northeastern regions, creating favourable conditions for the flu virus to spread. As a result, the northeast has experienced a significant rise in cases, while Bangkok has seen a less noticeable increase. Since the beginning of this year, flu cases have surpassed 100,000.
Dr Yong also mentioned that while flu cases have surged, the total number for the entire year is expected to be on par with last year’s figures. As the summer season approaches, flu cases are likely to decline, but a rise in cases is anticipated when schools reopen in May. By then, many individuals will have developed some immunity, and ongoing prevention campaigns will help curb the spread.
The widespread availability of Antigen Test Kits (ATK) has also contributed to the increased detection of flu cases, making it easier to identify infections and resulting in higher reported case numbers.
Dr Weerawat Manosuthi, spokesperson for the Department of Disease Control, explained that Oseltamivir is available to treat influenza and reduce its severity. He urged people in seven high-risk groups to receive annual flu vaccinations to boost their immunity.
Influenza A is the predominant strain detected, with two major subtypes: A(H1N1) and A(H3N2). As for avian influenza, global reports continue to emerge, especially concerning the A(H5N1) strain, which can be transmitted from animals to humans.
In the United States, from January 1, 2024, to February 14, 2025, there have been 68 confirmed cases of avian influenza, with one death. The latest case was reported on January 6.
Thailand has not reported any new confirmed cases of avian influenza since 2006. The country maintains a robust surveillance system for avian influenza in humans, animals and wildlife, and continues to assess the associated risks. The public is advised to avoid contact with sick or dead poultry and mammals.
Dr Weerawat raised concerns about the possibility of avian influenza and seasonal influenza outbreaks coinciding. If this occurs, it could lead to a genetic exchange between the two viruses, potentially allowing avian influenza, typically transmitted from animals to humans, to mutate into a human-to-human transmissible strain, similar to the seasonal flu.
