Mexico Reports HPAI H5N2 For the 1st Time in Nearly 30 Years

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Long before the emergence of the Asian lineage of the HPAI H5N1 virus in Guangdong Province in the mid-1990s, both LPAI (Low path avian influenza) and HPAI (High path) H5 viruses circulated in wild birds and poultry around the globe.   

The earliest known HPAI H5 virus was A/chicken/Scotland/59 (H5N1), which killed two flocks of chickens in Scotland in 1959. China's H5N1 virus rose to fame because it was the first HPAI H5 virus known to infect and sicken humans. 

During the 1980s and 1990s, a North American lineage of LPAI and HPAI H5N2 infected poultry flocks in the United States, Mexico, and the Dominican Republic.  The USDA cites two major outbreaks:

• The 1983-84 HPAI H5N2 outbreak resulted in humanely euthanizing approximately 17 million chickens, turkeys and guinea fowl in Pennsylvania and Virginia to contain and eradicate the disease.
•  In 2004, USDA confirmed an HPAI H5N2 outbreak in chickens in Texas. The disease was quickly eradicated thanks to close coordination and cooperation between USDA and State, local, and industry leaders.   

Mexico dealt primarily with LPAI H5N2 until the mid-1990s, when an outbreaks of HPAI H5N2 in Puebla, Mexico prompted the government to adopt poultry vaccination. Over the past 30 years, Mexico's LPAI H5N2 has reportedly diversified into 5 distinct clades (see Evolutionary Dynamics of Mexican Lineage H5N2 Avian Influenza Viruses). 

This week, for the first time since June of 1995, Mexico is reporting HPAI H5N2 on a non-commercial poultry farm with 117 free-range birds.  The WAHIS report states:

EPIDEMIOLOGICAL COMMENTS

The presence of highly pathogenic avian influenza (HPAI) virus subtype H5N2 was confirmed through PCR tests, virus isolation, genetic sequencing and intravenous pathogenicity index (IVPI) test, in the state of Michoacán, in a backyard farm. The premises have no contact with other poultry because no commercial poultry farm is implemented in the municipality. The sanitary situation of Mexico regarding this disease remains unchanged, since HPAI subtype H5N2 is not present in birds defined as "poultry" at the moment.

SENASICA is furthering its epidemiological investigation of the event and continues to urge poultry farmers to reinforce biosecurity measures on their farms and to immediately notify any anomaly observed in their animals, in order to protect national poultry production. The active epidemiological surveillance program is being maintained in technified production units, backyards, federally inspected slaughterhouses and municipal slaughterhouses as well as the monitoring of wild birds at national level.

Mexico's SENASICA reports:

Highly pathogenic AH5N2 avian influenza registered in a backyard unit in Michoacán

This epidemiological event does not represent a risk to human health, since the virus is exclusive to birds, nor does it affect the supply of chicken and eggs for the country.

National Agri-Food Health, Safety and Quality Service | March 27, 2024 | Release

The General Directorate of Animal Health of Senasica highlighted that commercial poultry farming is not involved.


The National Agri-Food Health, Safety and Quality Service (Senasica) confirmed the presence of highly pathogenic avian influenza (HPAI) AH5N2 in a free-range family production unit in Huetamo, Michoacán.

The General Directorate of Animal Health (DGSA) of Senasica highlighted that commercial poultry farming is not involved, explaining that the virus was detected in an isolated area and there are no commercial poultry farms registered in at least 100 kilometers around, therefore that the outbreak does not compromise the animal health status of our country.

This epidemiological event does not represent a risk to human health, since the virus is exclusive to birds, nor does it affect the supply of chicken and eggs for the entire country, which is why an increase in the prices of these poultry products is not seen. .

The agency of the Ministry of Agriculture and Rural Development reported that doctors from the Directorate of the Mexico-United States Commission for the Prevention of Foot and Mouth Disease and other Exotic Animal Diseases (CPA) of the DGSA began the investigation after A veterinarian reported high mortality on a farm that raised birds for self-consumption, in which, of a total of 120 birds, 117 had died at the time of the report.

Given the discovery, the DGSA immediately ordered the backyard unit to be quarantined and the CPA doctors applied the necessary counter-epidemic measures to deactivate the outbreak, such as cleaning, disinfection and establishing a sanitary vacuum period.

The first molecular biology RT-PCR results issued by official laboratories confirmed the presence of an H5 avian influenza virus, subsequently, through specialized tests, including viral isolation, primary genomic sequencing and the intravenous pathogenicity index. , it was confirmed that it was a highly pathogenic H5N2 avian influenza virus.

Agriculture's specialists in animal health emergency care carry out the corresponding investigations in the area to determine the origin of the infection. The activities carried out in the field are perifocal tracking in the surrounding properties and promotion of notification. Additionally, monitoring of wild birds found near the affected site was implemented in order to determine the source of contagion.

At this time, the official DGSA laboratories are carrying out deep genetic sequencing studies with the purpose of determining the possible origin of the virus.

Senasica urged poultry producers throughout the country not to let their guard down and strengthen biosafety measures in their poultry production units, both family and commercial, with the purpose of mitigating the risk of infections in domestic birds.

The highly pathogenic AH5N2 virus was identified in Mexico in commercial flocks in 1994 and was eradicated in 1995. Since then, our country has remained free of this highly pathogenic agent.

Any person who produces, processes, handles, moves or markets birds must immediately report to the health authority any abnormal behavior in their flocks, unusual mortality or any other suspicion of this disease to the telephone number 800 751 2100, or from their mobile phone through of the “AVISE” app, available for Android devices.

It isn't clear whether this H5N2 virus is a reassortment of HPAI H5N1 clade 2.3.4.4b, or a new incarnation caused by the spontaneous mutation of an LPAI H5 virus into an HPAI (see graphic below).

The fact that it was detected in a small, non-commercial flock, in a relatively remote region of Mexico may help contain this incident.  But given HPAI H5's tendency to overachieve, it's worth our keeping an eye on.