ALERT: First Human Case of Avian Influenza A(H5N2) Confirmed in Mexico

 

First Human Case of Avian Influenza A(H5N2) Confirmed in Mexico

On May 23, 2024, the Mexico International Health Regulations National Focal Point (IHR NFP) reported to the Pan American Health Organization/World Health Organization (PAHO/WHO) a confirmed case of human infection with the avian influenza A(H5N2) virus. The case involved a 59-year-old resident of the State of Mexico, who was hospitalized in Mexico City and had no known exposure to poultry or other animals. The patient, who had multiple underlying health conditions, had been bedridden for three weeks prior to the onset of acute symptoms.

The patient developed fever, shortness of breath, diarrhea, nausea, and general malaise on April 17, sought medical attention on April 24, and was hospitalized at the National Institute of Respiratory Diseases "Ismael Cosio Villegas" (INER). Unfortunately, the patient passed away the same day due to complications.

Initial RT-PCR testing of a respiratory sample at INER on April 24 indicated a non-subtypeable influenza A virus. Further sequencing at the Center for Research in Infectious Diseases (CIENI) confirmed the sample as influenza A(H5N2) on May 8. The Institute of Epidemiological Diagnosis and Reference (InDRE) validated these results on May 20, and sequencing confirmed the A(H5N2) subtype on May 22.

An epidemiological investigation identified 17 hospital contacts, one of whom reported a runny nose but tested negative for influenza and SARS-CoV-2. Additionally, 12 contacts near the patient’s residence were tested, with all samples returning negative results for these viruses. Serological sample results are pending.

Recent outbreaks of avian influenza A(H5N2) in poultry were noted in Michoacán, Texcoco, and Temascalapa. However, no direct link to these outbreaks has been established for this human case.

Epidemiological Insights: 

Avian influenza viruses typically infect animals but can occasionally infect humans, usually through direct contact with infected animals or contaminated environments. Human infections can range from mild to severe and may be fatal. Diagnosis requires laboratory testing, and antiviral drugs like oseltamivir can reduce viral replication and improve survival in some cases.

Public Health Response: 

Mexican health authorities have implemented several measures, including:

• Conducting an epidemiological investigation of the case and contacts.
• Monitoring health care workers and surveillance of respiratory illnesses in neighboring municipalities.
• Analyzing trends in pneumonia, bronchopneumonia, acute respiratory infections, and conjunctivitis.
• Training on preparedness, prevention, and response to zoonotic influenza events.
• Strengthening surveillance in poultry and wild birds near the patient's residence.

PAHO/WHO has also reinforced surveillance and diagnostic capacities and is conducting regular risk assessments.

WHO Risk Assessment: 

This is the first global report of a human infection with influenza A(H5N2) and the first H5 virus infection in Mexico. Human cases from exposure to infected poultry or environments are not unexpected. While no further human cases associated with this A(H5N2) case have been detected, the overall risk to the general population is currently assessed as low.

WHO Advice:

WHO emphasizes the importance of global surveillance and timely sharing of information. Enhanced surveillance is necessary in areas with outbreaks of animal influenza. Travelers to affected regions should take precautions, such as avoiding contact with animals and practicing good hygiene. All novel influenza A virus infections in humans must be reported under the IHR. WHO does not recommend special screening at points of entry or travel restrictions.

This situation underscores the need for continued vigilance and collaboration to detect and respond to zoonotic influenza viruses promptly.

- Lavanya Yadav@Wondernext