Dr. Marie-Anne Rameix-Welti, Medical Director of the Respiratory Infections Center at the Pasteur Institute recently expressed her concern over the possible emergence of H5N1 avian influenza as a pandemic virus. The Pasteur Institute was at the forefront of research on the virology and epidemiology of COVID-19 and is an established World Health Organization reference center for influenza.
It is emphasized that at this time H5N1 infection is mainly confined to wild bird and commercial poultry populations with spillover to marine and some terrestrial mammals. There is no evidence of widespread infection of humans and most importantly no record of human-to-human transmission. This property of the virus would be a prerequisite for emergence of an epidemic or pandemic strain. Despite extensive exposure of populations in close contact with poultry, there have been less than 1,000 confirmed outbreaks of H5N1 and other avian strains among humans over the past 20 years. Most cases occurred in Asia although with a high fatality rate especially among children and the elderly with intercurrent predisposing conditions.
Dr. Rameix-Welti noted that a “bird flu pandemic would probably be quite severe potentially even more disruptive than the pandemic (COVID-19) we experienced.” She noted that most world populations have antibodies to H1 and H3 seasonal influenza but lack protection against H5. Although there is concern over a potential H5 pandemic, officials at the World Organization for Animal Health consider the risk low but stress the need for preparation. This sentiment is endorsed by Dr. Rameix-Welti who pointed to an inventory of antivirals and extensive experience in containment gained during the COVID-19 pandemic.
Implicit in prevention of an outbreak is the need to suppress avian influenza in large commercial flocks. Intense biosecurity has not materially reduced the incidence of outbreaks but in the U.S. small commercial egg units in the Midwest are impacted in addition to turkey growing farms and in backyard flocks across all four migratory flyways.
Given the persistence of seasonal outbreaks, the susceptibility of commercial poultry, concentration in limited geographic areas there is ample opportunity for mutations to occur among circulating H5N1viruses. Both point mutations and recombinant events could result in an ability to infect humans and even to establish contagion. Vaccination of at-risk farms and species would reduce the probability of emergence of a zoonotic strain.
Preventive vaccination as employed in the E.U., Mexico and other nations in combination with biosecurity is currently opposed by a segment of the industry reliant on exports. Over the intermediate future, the possible loss of exports should be balanced against the consequences of the low probability of emergence of a zoonotic avian influenza strain although with a catastrophic outcome. Even over the short term, endemic avian influenza carries a high cost to the public and private sectors and above all as a result of an escalation in shelf prices of eggs and turkey products. This financial burden far outweighs the value of exported broiler leg quarters.