An article recently published in the peer-reviewed journal draws attention Clinical Researchedited by the Dr. Américo Negrette Clinical Research Institute of the Faculty of Medicine of the University of Zulia (LUZ). It is titled: The current avian influenza A (H5N1) pandemic-preparedness/” title=”Wendy Barclay: Navigating the Evolution of … Bird Flu and … Preparedness”>panzootic and its potential pandemic threat. The authors of this review are doctors Flor Pujol, Individual of Number (Seat XVI) of the Academy of Physical, Mathematical and Natural Sciences of Venezuela (Acfiman) and emeritus researcher of the Venezuelan Institute of Scientific Research (IVIC), and José Esparza, Foreign Corresponding Member of the National Academy of Medicine of Venezuela and professor at the University of Maryland in Baltimore, USA.
The objective of the study was to evaluate the possibility of the current avian influenza A (H5N1) panzootic becoming a pandemic and examine the critical measures necessary for preparedness and prevention. “While it remains impossible to predict with certainty when or how a new influenza pandemic might emerge, the current spread of the avian influenza A (H5N1) virus is deeply concerning and requires urgent preparedness efforts,” say Drs Pujol and Esparza.
Breaking down words
According to the Pan-Hispanic Dictionary of Medical Terms of the Royal National Academy of Medicine of Spain, panzootic is an “epizootic that affects many countries on different continents”, epizootic understood as “a common disease of one or more animal species that live in a specific geographical area and that occurs with an incidence above that expected for a certain period of time”. If there are still doubts, the Spanish dictionary clarifies that “panzootia” is the equivalent of the term “pandemic” and “epizootia” is the equivalent of “epidemia”, but referring to animal diseases. In short, panzootia is a pandemic that spreads between animals, not humans.
For its part, the World Health Organization (WHO) defines influenza or flu as an acute respiratory infection caused by influenza viruses (belonging to the family Orthomyxoviridae), very common in the world and whose patients (the majority of them) usually recover without treatment. Of the four types of influenza viruses (A, B, C and D), A and B are the causes of seasonal epidemics of respiratory infections in humans, with high pandemic potential. In the case of influenza A virus, the natural reservoirs are aquatic birds (which end up affecting people through other mammals), which is why it is considered a zoonosis.
Avian influenza A viruses can be classified into two forms, depending on their virulence in birds: low pathogenicity and high pathogenicity. The first appearance of the highly pathogenic avian influenza A (H5N1) virus dates back to 1996 and, since then, 990 human infections have been reported in 24 countries, with a case fatality rate close to 50%. As an important point, the authors highlight that the lethality in humans associated with this panzootic appears to be lower.
Venezuela Case
The panzootia analyzed by Venezuelan scientists in Clinical Research It is caused by subclade 2.3.4.4b of the highly pathogenic avian influenza A (H5N1) virus. This animal pandemic began at the end of 2021, but reached Venezuela the following year. “For the first time here and in other South American countries, migratory birds introduced avian influenza to our hemisphere, causing great mortality, particularly of wild pelicans,” recalled the Acfiman academic, winner of the 2025 National Prize for Science, Technology and Innovation Dr. Humberto Fernández-Morán, Consolidated Research Group Mention, and member of the World Academy of Sciences (TWAS, for its acronym in Spanish). English) from 2026.
The Ministries of Science and Technology and Agriculture and Lands declared a health alert in December 2022 in the states of Anzoátegui, Miranda, Nueva Esparta, Vargas and Sucre. In addition to birds, the authorities found marine mammals without vital signs, probably due to having ingested infected avian specimens. Since 2023, no new cases have been reported.
The pig, among many
In order to be transmitted efficiently between people, avian influenza A viruses require certain changes – mutations, gene rearrangements (exchanges) with mammalian viruses – that often occur in an intermediate host. This intermediate host is usually the pig, since the porcine respiratory epithelium has receptors for mammalian and avian viruses. However, the pig has not yet played a relevant role in this panzootic.
Although the authors clarify that cattle are not usually infected with the influenza A virus, during the current panzootic some cows in Texas (and later other US states) contracted the avian influenza A (H5N1) virus. “In cattle, the primary site of virus replication appears to be the udder, since the mammary tissue expresses avian-type receptors. This raises the possibility of transmission of the virus through unpasteurized milk,” the experts say in the publication. In total, nearly fifty species of terrestrial and marine mammals have become ill due to the animal pandemic caused by the influenza A (H5N1) virus.
Pandemic jump
What must happen for a panzootic to become a pandemic? Doctors Pujol and Esparza cite as a prerequisite that the virus acquires the capacity to infect humans and maintain efficient transmission between them, “something that has not happened to date.” Efficient transmission “probably requires the cumulative acquisition of several key mutations.” For now, subclade 2.3.4.4b has acquired only some of the multiple mutations necessary for transmission between human beings to become effective. However, the authors warn that the extensive geographic distribution of this subclade and its ability to infect a wide range of mammalian hosts “raise important concerns about the possible emergence of a pandemic strain.”
Pre-existing immunity to seasonal human influenza viruses is also a deciding factor, either from prior infection or vaccination. An important barrier that slows transmission is the reduced stability of the virus in acidic or low pH environments, such as the human upper respiratory tract.
The last part of the article presents a roadmap that countries must develop to respond, both at the community, national and international level, to a possible influenza pandemic, following the WHO guidelines. “A coordinated One Health approach – integrating human, animal, environmental health and, of course, vaccines – is essential to effectively address this evolving threat,” they conclude.