Explainer: How worrying is H5N1 bird flu’s growing spread, and will S’pore be affected?

SINGAPORE — Earlier this week, the World Health Organization (WHO) voiced concerns at H5N1 bird flu’s growing spread to new species, including humans who face an “extraordinarily high” mortality rate if infected.

The United Nations health agency said the avian influenza A, or H5N1 bird flu virus strain, has also been detected in very high concentrations in raw milk from infected animals, though it is not known how long the virus can survive in milk.

The H5N1 strain was first detected in birds in 1996 and has primarily been a threat to farmed and wild fowl.

Since 2020, however, the number of outbreaks in birds has grown exponentially, alongside an increase in the number of infected mammals.

This contact with mammalian populations has led WHO’s chief scientist Jeremy Farrar to sound alarm bells.

Nevertheless, while humans have been infected with this flu strain – usually through contact with infected birds and livestock – there is currently no evidence to show that it can be spread from human to human.

TODAY looks at the global bird flu outbreak, how Singapore has remained bird flu-free, what might happen if the country faces infections and what precautions ought to be taken to prevent this.

HOW WORRYING IS THE CURRENT BIRD FLU SITUATION?

While there is currently no evidence of human-to-human spread of the virus, in cases where humans have been infected through contact with animals, the mortality rate has been “extraordinarily high”, Dr Farrar has said.

Between the start of 2023 and April 1 this year, the WHO recorded 463 deaths from 889 human cases across 23 countries. This puts the case fatality rate at 52 per cent.

Furthermore, Dr Farrar said that the virus’ contact with the mammalian population means it’s “getting closer to humans” and warned that the virus is “just looking for new, novel hosts”.

He expressed “great concern” that it may also critically evolve towards human-to-human transmission.

“We have to watch – more than watch – we have to make sure that if H5N1 did come across to humans with human-to-human transmission, that we were in a position to immediately respond with access equitably to vaccines, therapeutics and diagnostics,” said Dr Farrar.

In Singapore, there are currently no known cases of the H5N1 bird flu.

Dr Paul Tambyah, president of the International Society for Infectious Diseases, told TODAY: “In terms of natural spillover, I am not very concerned about the current strain as this has occurred many times in the past with previous strains which were far more fatal in humans.”

He also pointed out that the disease has remained endemic, with relatively low numbers of cases in humans, in this region.

HOW HAS SINGAPORE REMAINED BIRD FLU-FREE?

Dr Tambyah said that Singapore has remained free from highly pathogenic strains of avian influenza mainly due to its strict biosecurity measures and surveillance.

The country also benefits from comprehensive animal vaccination programmes in other countries in the region – which have kept the number of infections down in domestic birds – and biosecurity programmes which have managed to keep infected wild birds from contaminating domestic flocks.

“To be honest, however, I think that both (Singapore and Malaysia) have been fortunate in that H5N1 does not appear to be that rapidly transmissible outside of the cramped conditions of ‘factory farms’, which are relatively easy to control,” said Dr Tambyah.

However, he cautions that this might change if scientists decide to modify the virus to become more transmissible, with the aim of developing rapid vaccines and treatments for the novel strain.

In 2019, Science Magazine, an academic journal of the American Association for the Advancement of Science, reported about controversial lab studies that modify bird flu viruses in ways that could make them more risky to humans. 

Advocates of such studies say that the research can help public health experts better understand how viruses might spread, so they can plan for pandemics. 

“But by enabling the bird virus to more easily spread among mammals, the experiments also raised fears that the pathogen could jump to humans,” the report said.

“And critics of the work worried that such a souped-up virus could spark a pandemic if it escaped from a lab or was intentionally released by a bioterrorist.”

Nevertheless, Dr Tambyah said he believes such a scenario is unlikely, as there are renewed efforts to ensure good lab safety. 

In the case of an unfortunate accident, there are also protocols in place to monitor lab scientists and to ensure that any exposure is screened and protected, he added.

WHAT PRECAUTIONS SHOULD BE TAKEN LOCALLY?

On how an outbreak might impact Singapore, Dr Tambyah said that Singapore’s diversification of its food supply means that it will be less vulnerable to a shutdown in beef or chicken supplies from one or two major countries.

According to the Singapore Food Agency’s (SFA) Singapore Food Statistics 2022 report, Singapore can import poultry from 30 countries, processed eggs from 26 countries and shell eggs from 17 countries.

Beyond diversifying import sources, Dr Tambyah pointed out that Singapore also has good links with its neighbouring countries. This allows them to share resources that can protect their people from a range of infectious diseases, including but not limited to bird flu.

Still, precautions ought to be taken to guard against infections.

On a national level, the authorities will need to continue supporting the ongoing biosurveillance work of different agencies, such as the SFA, the National Environment Agency, and the Animal & Veterinary Service, said Dr Tambyah.

In December last year, for example, Singapore suspended its import of raw poultry and poultry products from several regions in countries affected by an outbreak of the highly pathogenic H5N1 avian influenza.

The Wildlife Reserves Singapore (WRS) – which operates Jurong Bird Park, Night Safari, River Safari and Singapore Zoo – said on its website that it also works closely with the Agri-Food and Veterinary Authority to take precautionary measures against bird flu.

This includes the implementation of “stringent bio-security measures” at its parks, such as vaccinating all birds that are free ranged and exposed to the public, and giving flu injections to its staff. 

The parks also conduct periodic bird flu drills for its staff and train them to monitor the birds daily for symptoms of illness, said WRS.

To date, there have been no known cases of bird flu in any of the parks or in the country, it added.

At an individual level, Dr Tambyah said that Singaporeans should be sensible in avoiding contact with sick birds or animals. They should also practise good hand hygiene when handling animals at petting zoos, farmstays or other similar places.

Should one fall sick, he or she should also seek medical attention promptly, he added.