Bird flu nears Thai border as neighbouring country reports more cases

Thailand has reported no confirmed cases of H5N1 avian influenza in nearly 20 years, but the global situation remains concerning, with ongoing reports of human infections and outbreaks in some regions.

From January 1, 2003, to May 27, 2025, there have been 976 confirmed human cases of H5N1 worldwide, with 470 fatalities—a case fatality rate of 48.2%. Of particular concern for Thai health authorities is the situation in Cambodia, which shares a border with Thailand.

Cambodia reports 12 cases in 2025, including 7 within one month

As of July 3, 2025, Cambodia has confirmed 12 human cases of H5N1 so far this year. Alarmingly, seven cases were reported in just one month, between June 7 and July 3.

The most recent case, confirmed on 3 July, involved a five-year-old boy from Angkor Chey district, Kampot province. 

According to an official statement by Cambodia’s Ministry of Health, the boy tested positive for H5N1 following laboratory testing by the National Institute of Public Health.

The child reportedly developed fever, cough, difficulty breathing, and rapid breathing, and is currently receiving close medical supervision. An investigation revealed that his family keeps around 40 chickens, two of which had fallen ill and died, and that the boy regularly played with the birds.

Emergency response activated

National and local response teams from Cambodia’s Ministry of Health, in coordination with agricultural authorities and local officials, have been actively investigating the outbreak. Efforts include identifying the source of infection in both animals and humans, and tracing and monitoring close contacts to prevent further community transmission. Antiviral Tamiflu has been distributed to at-risk contacts, and health education campaigns have been launched in affected villages. Despite the rapid spread among poultry, there is no evidence so far of human-to-human transmission.

Previous case confirmed in a 19-month-old boy from Takeo

On July 1, 2025, while Cambodia had yet to make an official announcement regarding its 11th case, the infection was confirmed in updates from the Centre for Infectious Disease Research and Policy (CIDRAP), Hong Kong’s Centre for Health Protection (CHP), and the World Health Organisation (WHO).

The case involved a 19-month-old boy from Takeo province, who died from the infection. His symptoms began on June 7, and his death was reported on June 30.

New reassortant strain of H5N1 spreading rapidly in Cambodia, experts warn

The Centre for Medical Genomics at Ramathibodi Hospital, Mahidol University, has raised concerns over the current outbreak of H5N1 avian influenza in Cambodia, noting that it may involve a new reassortant strain of the virus.

According to the centre, genetic sequencing suggests the outbreak could be linked to a novel strain resulting from reassortment between two clades of H5N1: the regional clade 2.3.2.1c, which has circulated in Southeast Asia for years, and clade 2.3.4.4b, a globally dominant strain. The new strain has been provisionally designated clade 2.3.2.1e.

Pattern resembles early 2000s bird flu outbreaks

This reassortant strain has reportedly caused clustered community outbreaks following mass die-offs of poultry, reminiscent of the epidemic patterns observed in Thailand and the region between 2004 and 2016.

The unusually high number of human infections across multiple Cambodian provinces in just a few weeks suggests that the virus is spreading rapidly among local poultry. Experts confirm that the virus responsible is indeed a newly mixed strain combining local and global lineages.

The Centre for Medical Genomics stressed that scientists are closely monitoring the situation, as each transmission of the virus to humans offers an opportunity for the virus to mutate and adapt further to human hosts—a process that could eventually lead to increased transmissibility or severity.

Three key concerns surrounding the current H5N1 situation

1. Emergence of a reassortant strain:

Genetic changes are common in influenza viruses, and the new clade 2.3.2.1e may possess unique properties that differentiate it from previous strains. Scientists are currently analysing its characteristics in detail.

2. Rising number of human cases:

Intermittent human infections provide virologists with crucial opportunities to study how the virus adapts to human biology. Such data are vital for ongoing risk assessments.

3. High case fatality rate:

Historically, H5N1 has been associated with severe illness in humans. According to data from the World Health Organization (WHO), the virus has a case fatality rate of approximately 52% among confirmed human infections.

Future risk of H5N1: Experts warn of potential pandemic deadlier than Covid-19

To highlight the urgency of prevention, medical experts have stressed that if the H5N1 virus evolves to enable sustained human-to-human transmission, it could pose a far more severe public health challenge than Covid-19.

The primary concern lies in the difference in fatality rates: while COVID-19 has a case fatality rate of less than 1%, H5N1 has historically shown a mortality rate as high as 52%. Though this figure could decline in a full-scale pandemic due to wider testing and detection, it would likely remain alarmingly high—with projections suggesting that such a scenario could result in 50 to 100 million deaths globally or more.

A scenario the world must avoid

Public health experts have modelled a worst-case scenario, which underscores why global prevention efforts are so critical.

Week 1: The crisis begins. The World Health Organization (WHO) confirms sustained human-to-human transmission of H5N1. Air travel is suspended, borders slam shut, and global markets plunge.

Month 1: Health systems collapse under the weight of severe cases and soaring death tolls. Hospitals become triage battlegrounds, where doctors are forced to prioritise patients with the highest chance of survival.

Six months onward: The world grinds to a halt. Global supply chains break down, economies collapse, and societies are gripped by fear and instability. The only hope lies in the rapid development and deployment of a vaccine.

Thailand maintains vigilant monitoring of H5N1 amid rising regional cases

Dr Jurai Wongsawat, senior expert and spokesperson for Thailand’s Department of Disease Control (DDC), has confirmed that while Thailand remains at low risk of H5N1 avian influenza transmission, heightened surveillance continues nationwide, particularly in light of the rising number of human infections in neighbouring Cambodia.

Jurai explained that the virus currently circulating in Cambodia is a highly pathogenic strain, classified as Clade 2.3.2.1e. This strain has been detected in countries across the Mekong region, including Cambodia, Vietnam, and Laos. In contrast, the strain spreading in the United States, Europe, and other global regions—Clade 2.3.4.4b—is considered less severe in terms of pathogenicity.

One Health strategy reinforces national vigilance

Thailand employs an integrated One Health surveillance approach, combining efforts from the Department of Disease Control, the Department of Livestock Development, and the Department of National Parks, Wildlife and Plant Conservation. This collaboration includes:

• Monitoring animal health, particularly among poultry and wild birds
• Screening poultry farms in high-risk areas
• Assessing potential zoonotic transmission risks
• Public health advice

Authorities advise the public to:

• Eat only well-cooked food, particularly poultry, eggs, and dairy products
• Avoid contact with sick or dead animals, including poultry, pigs, and cattle
• Seek medical attention immediately if experiencing flu-like symptoms—such as fever, cough, shortness of breath, or conjunctivitis
• If large numbers of sick or dead birds are found, residents should report the incident to local livestock officials.

Travel guidance for at-risk areas

Travellers to affected or high-risk countries are advised to:

• Follow local health updates and advisories
• Purchase travel health insurance

Practise good personal hygiene

• Avoid contact with birds, including wild birds, feathers, and droppings
• Consume only thoroughly cooked food
• Individuals returning from countries with known H5N1 outbreaks—such as Cambodia, the United States, Mexico, India, Canada, the UK, France, Germany, the Netherlands, Pakistan, Vietnam, Taiwan, and Brazil—should monitor their health for two weeks. If symptoms such as high fever, cough, or sore throat appear, they should seek medical attention and inform doctors of their travel history.

Thailand continues to strengthen its preparedness and response systems to minimise risk while urging the public to remain informed, cautious, and cooperative.