What to tell colleagues and patients about avian influenza (‘bird flu’)

An “early release” article in the Canadian Medical Association Journal highlights five things that we should know about the highly pathogenic avian influenza H5N1 virus: It is spread globally by wild birds. Outbreaks have occurred on poultry farms, in backyard flocks and in wild birds. Viral spillover from birds has led to infections in mammals, including cattle and humans, leading to the potential for a pandemic. However, the mechanisms of transmission are not fully known.1 As of June 12, 2024, no reported human cases of H5N1 have been acquired in Canada. However, nearly 900 human cases of H5N1 have been reported globally since 2003, with a fatality rate of 52%. Clinical presentation may vary from mild to severe influenza. Recently in the United States, dairy workers who became infected presented with hemorrhagic conjunctivitis.1Healthcare providers should ask about animal exposures in people who present with influenza-like illness, conjunctivitis or (less commonly) meningoencephalitis. People with significant exposure to livestock or wildlife may be at risk for H5N1 infection. However, the risk to the general public is currently low, with no evidence of sustained person-to-person transmission.1Usual lab-based testing may identify the highly pathogenic avian influenza H5N1 virus as influenza A virus. For suspected infections, confirmatory testing should be conducted at a provincial or national reference lab. It is important to identify patients with exposure histories as soon as possible. If the patient has eye symptoms, collect nasopharyngeal and conjunctival swabs, and inform public health about cases under investigation.1Currently, no vaccine exists for public use in Canada. The antiviral, oseltamivir, is recommended for treatment and prophylaxis of highly pathogenic avian influenza infection. It should be started as soon as possible in a person with a suspected infection, or after close contact with a confirmed case of highly pathogenic avian influenza.1Health professionals can gain more detailed information about avian influenza A(H5N1) infection from a Health Canada website.2 Health Canada reports that government authorities are currently responding to the outbreak of influenza A(H5N1) in farmed birds and wildlife across Canada. Human cases have primarily occurred due to zoonotic transmission through direct contact with infected birds (dead or alive) or contaminated environments (e.g., live animal markets, poultry farms). Human-to-human transmission is rare and there has been no evidence of sustained transmission between humans. Thorough cooking of animal products (e.g., poultry, beef, game meat, organs, eggs) and pasteurization of milk/milk products will kill the virus. It is currently unknown if influenza A(H5N1) viruses can readily be transmitted through consumption of raw or undercooked animal products.2Health Canada notes that most human cases have a history of exposure to dead or ill poultry, with a usual incubation period of one to five days (up to 9 days) after exposure. The virus mainly affects the respiratory tract, but can also cause gastrointestinal or central nervous system manifestations. Symptoms may include cough, fever, shortness of breath, diarrhea (in severe cases), headache, myalgia, sore throat, rhinorrhea, mucosal bleeding, fatigue, jaundice and conjunctivitis. Respiratory failure is the most common cause of death. Other complications may include multiorgan failure, pulmonary hemorrhage, pneumothorax and pancytopenia.2Oseltamivir or zanamivir can be effective in reducing morbidity and mortality, especially if administered early in the course of illness, ideally within the first 48 hours of onset. Baloxavir and intravenous peramivir may be requested through Health Canada’s Special Access Program on a case-by-case basis. Due to increased reports of antiviral resistance, amantadine is not recommended for use as a monotherapy for avian influenza. Combination therapy using antivirals with different mechanisms of action may be considered for select cases at risk of antiviral-resistant infection with monotherapy (e.g., immunocompromised patients). Currently, there is insufficient evidence to suggest added benefit from adjunctive therapies (i.e., corticosteroids, macrolide antibiotics, passive immune therapy) in patients with avian influenza A(H5N1). Seasonal influenza vaccines do not offer protection against influenza A(H5N1).2 The Health Canada website also provides greater detail on preventing avian influenza A(H5N1) infections, including information for people who work with animals or in higher-risk environments, as well as recommendations for travellers.2 The US Centers for Disease Control and Prevention also has a website that is updated daily, to keep people informed of the current situation regarding avian influenza in the United States.3References:Kozak R, Bogoch II, Mubareka S. Highly pathogenic avian influenza A (H5N1) virus. CMAJ 2024; early-release June 12, 2024. (accessed June 18, 2024).Government of Canada. Avian influenza A(H5N1): for health professionals. (accessed June 18, 2024).Centers for Disease Control. H5N1 bird flu: current situation. (accessed June 18, 2024).

What to tell colleagues and patients about avian influenza (‘bird flu’)

Register for free access or login.

Related Topics