Bird flu: An infection most ‘fowl’

The risk for humans to contract bird flu is usually through either direct or indirect exposure to infected animals and/or their contaminated environment. — Filepic

Influenza (flu) is a common respiratory infection caused by influenza viruses A and B.

It occurs all year round in Malaysia, unlike in temperate climates where it is seasonal, being more common in autumn and winter.

The features of flu include:

• Fever and chills
• Cough, sore throat and stuffy nose
• Muscle aches, joint pains, headaches and fatigue (feeling very tired), and/or
• Nausea, vomiting and diarrhoea (more common in children).

The symptoms may last for more than a week.

Some people only have mild symptoms for a few days, especially if they have some immunity from a previous infection or vaccination.

Others can get very sick and may have complications like lung infection (pneumonia) or breathing difficulties, which require hospitalisation.

These complications can occur in anyone, but are most likely in those at increased risk, i.e. children below five years old, senior citizens, pregnant women, and those with medical conditions like diabetes, obesity, and chronic lung, heart or kidney disease.

Annual flu vaccination is effective in preventing severe infection.

It is needed every year as the influenza virus strains change (mutate) constantly.

The vaccines are prepared annually to best match the strains predicted for the upcoming flu season.

Keeping an eye out

Avian influenza, commonly termed “bird flu”, is caused by the avian influenza virus A.

This virus is usually found in wild water birds like ducks, geese, swans, etc.

Infected birds shed the virus in their saliva, nasal secretions and faeces, which can then spread to domestic poultry, as well as other bird and animal species.

It was reported to have infected 300 bird species and at least 70 mammalian species, including seals, sea lions and minks, in 2024.

Malaysia first reported an avian flu outbreak in poultry in Kelantan, Kuala Lumpur and Perak in 2004.

The virus was again detected in Kuala Lumpur, Perak and Penang in 2006, and in Selangor, Kuala Lumpur and Kelantan in 2007.

The last outbreak in 2017 affected poultry in Kelantan.

Avian flu has also infected humans, with the first case reported in Hong Kong in 1997, which sparked fear of a potential epidemic at the time.

Since then, multiple cases were reported in United States, Canada, Australia, China, Cambodia and Vietnam.

The World Health Organization (WHO) and the US Centres for Disease Control and Prevention (CDC) have assessment tools for the risk of avian flu.

The WHO tool assesses the risk of avian flu with pandemic potential, while the US CDC tool classifies 24 novel influenza A viruses according to low, moderate or high risk.

Both tools assess the pandemic potential of each virus type; however, they cannot predict an influenza pandemic.

WHO publishes weekly situation reports on avian flu in humans.

The viruses of concern as at Dec 13, 2024, were:

• H5N1: 939 human cases and 464 deaths (Case fatality rate, CFR, 49%) in 24 countries since 2003 (as of Nov 1, 2024).
• H7N9: 1,568 human infections confirmed (in China, plus one imported case in Malaysia and two imported cases in Canada) since 2013, with 616 deaths (CFR 39%).

  No human cases have been reported since March 2019.

• H5N6: 93 human cases and 57 deaths (CFR 61%) in China and Laos.
• H9N2: 113 human cases and two deaths (CFR 2%) in China, Cambodia and Vietnam.

Limited cases of avian influenza H3N8, H5N2, H5N8, H6N1, H7N2, H7N3, H7N4, H7N7, H10N3, H10N5, H10N7 and H10N8 have also been reported in humans.

In February 2014, Malaysia reported to WHO a human case of avian flu in a tourist from Guangdong, China.

Bird contact

While human influenza viruses A and B infections are common in humans, avian flu is not and tends to occur mostly in people with close contact with infected animals.

Such individuals get infected either directly through handling, culling, slaughtering or processing sick animals, or indirectly, through environments contaminated with body fluids from such animals.

However, there have been recent reports of avian flu in individuals with no such exposure.

This means that even infected healthy individuals could be at risk for serious illness or death.

Exposure to avian flu can lead to human infection and disease ranging from mild, flu-like symptoms or eye infection, to severe, acute respiratory disease and/or death.

The severity of the infection is dependent on the virus type and the individual’s characteristics.

The estimated CFR of avian flu in humans is about 50%.

In a review of 30 reported cases in pregnant women, there was high maternal (90%) and infant (86.7%) death rates when avian flu infection occurred during pregnancy.

The current flu vaccines protect against select human influenza A and B viruses, but do not protect humans from avian flu viruses.

To keep in mind

Most patients with influenza-like illness are likely to be infected with the human influenza viruses A and B, or other common respiratory viruses.

However, avian flu has to be considered whenever there are features of acute or lower respiratory tract infections.

Of particular concern are infections, conjunctivitis or complications of acute respiratory illness without an identified cause, in combination with exposure to animals infected with avian flu viruses or environments contaminated by them, or close contact with someone known or suspected to be infected with avian flu, or who had unprotected exposure to live avian flu virus in a laboratory.

If an avian flu infection is suspected, it is incumbent on the attending doctor to:

• Notify the state/local health authorities
• Collect respiratory samples for virological tests
• Refer the patient to a public health facility where the patient will be isolated
• Commence antiviral treatment, and
• Institute infection control measures as soon as possible.

Supportive treatment may be necessary when indicated.

Prevention methods

The most effective way of preventing avian flu is to avoid contact with sick or dead animals, or environments contaminated by them, particularly in locations where avian flu outbreaks have occurred.

Individuals who have exposure to avian flu, including those responding to an outbreak, have to comply with the standard guidelines.

Healthcare personnel in contact with suspected or known cases of avian flu have to adhere strictly to infection prevention and control guidelines.

Although vaccines are available to protect birds from avian flu, it is not done in many countries because of practical considerations, e.g.:

• The logistics of vaccinating each individual bird
• Potential exposure risks to vaccinators
• Inability to test infected versus vaccinated birds
• Fears of viral mutation
• The effectiveness of the vaccine in multiple bird species.

However, countries where avian flu is endemic have had some success in vaccinating commercial poultry.

Candidate vaccines for human protection are available to be mass produced in the event of a pandemic.

Indeed, some governments have stockpiles of such vaccines for certain avian flu viruses that can be utilised should avian flu develop the ability to easily infect humans and human transmission becomes easier.

Vigilance needed

A multinational research team conducted a serological survey of 10,100 individuals from 2,650 households, of whom 51% were poultry farmers, in northern Sabah, in 2015.

A serological survey is a survey using blood tests on the population being studied.

They found antibodies against the H5 avian flu virus.

The researchers stated that these antibodies suggest that some individuals living near migratory bird sites may have been exposed to the avian flu virus.

This is relevant as there has been substantial loss of forests in Sabah and Sarawak, and several migratory birds are carriers of avian flu, including the H5N1 virus.

The authors stated: “There is a spatial and environmental overlap between individuals displaying high H5 binding and the distribution of migratory birds.”

Although, Malaysia has an influenza surveillance system, its reports in the public domain are limited.

There is currently no published data of time series forecasting in the prediction of future human and avian flu outbreak(s) in Malaysia.

The recent global increase in reports of human avian flu is a reminder of the need for increased serovigilance for avian flu in humans and animals.

Serovigilance, also known as serosurveillance, tests randomised leftover blood samples for antibodies that indicate the presence of microorganisms of interest.

Addressing this issue would increase disease awareness and help preparedness in prevention of an outbreak, which could have disastrous consequences.

Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. For more information, email [e-mail]. The views expressed do not represent that of organisations that the writer is associated with. The information provided is for educational and communication purposes only, and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.