The Centers for Disease Control and Prevention (CDC) has updated its guidelines for managing potential cases of zoonotic influenza, which can originate from avian or porcine sources. These new recommendations, presented in a Health Alert Network (HAN) advisory on February 24, 2025, incorporate feedback from healthcare professionals across the nation.

Defining Risk Exposures

• Direct Contact: Physical interaction with a human or animal confirmed to have avian or porcine influenza.
• Environmental Exposure: Prolonged presence (at least 15 minutes) in a contaminated environment, or contact with contaminated materials, including surfaces and samples infected by avian or porcine influenza viruses.
• Animal Suspicion: Interaction with an animal suspected of infection in a farming or wildlife setting, particularly birds, pigs, or mammals that are ill or deceased.

Individuals exposed to these risks must monitor their health closely for 10 days. If symptoms such as fatigue, fever, muscle aches, cough, or breathing difficulties arise, they should immediately:

• Consult a physician and inform about possible zoonotic exposure.
• Implement barrier measures, such as wearing a surgical mask and limiting contact with others.

Managing Possible Cases

Individuals exhibiting clinical signs compatible with a respiratory or ocular infection and having been exposed to a risk factor are considered possible cases.

• Clinical Evaluation: The healthcare provider should determine if the patient requires immediate hospital care,
• Lab Testing: Prescribe an amplification-free influenza test by RT-PCR for influenza A/B and subtypes H1N1/H3N2, ideally targeting nasopharyngeal, conjunctival, or deep respiratory samples.
• Notification: Clearly indicate on the prescription that the test is for a possible zoonotic influenza case,
• Hygiene Guidelines: Provide guidance on hygiene and prevention measures, as outlined in the documentation from the CDC.

“For any clinical form such as meningoencephalitis without an identified etiology with documented exposure to an animal suspected or confirmed with avian influenza, it will be necessary to suspect an avian flu and consider the patient a possible case,” the CDC advises.

New Virological Criteria

Recent updates include the consideration of the PCR amplification cycle, or the Threshold cycle (CT). This measure quantifies the viral load in samples. A CT less than 32 indicates a sufficient viral load to assert a probable case, particularly if the H1 and H3 subtypes are negative, suggesting a seasonal flu.

Cases with a CT greater than 32 are referred to the CDC if clinical and epidemiological suspicion remains strong. The decision-making algorithm for suspected zoonotic influenza cases has been updated to reflect these changes.

Reporting and Management of Probable Cases

Probable cases of zoonotic influenza must be reported immediately to the local health department by the attending physician. Confirmation involves collaboration between the health department and CDC, with support from an infectious disease specialist if necessary. The CDC clarifies, “when the CNR vitamins objectify proven presence of virus origin ‘central avian flu’ if associated cases if detected.”

• Contact Tracing: Identify individuals who have had close or direct contact with a probable or confirmed case within 48 hours before and up to 10 days after symptom onset.
• Consultation: A consultation between the CDC, public health agencies, specialists, and the National Center for Respiratory Infections ensures appropriate care for the patient and their contacts.

Additional information on managing confirmed zoonotic flu cases, including hygiene, treatment, and equipment disinfection, can be found in the recommendations from the Advisory Council for Disease Control and Prevention.

Avian Flu Overview

Highly pathogenic avian influenza (HPAI) is a virulent infection primarily affecting wild or domestic birds, causing mortality rates exceeding 90% in certain species. In this regard, the U.S. Department of Agriculture (USDA) classified avian flu as a high-risk pathogen, leading to biosecurity measures across poultry farms and establishments nationwide as of November 2024. “Biosecurity protocols include isolating affected areas, implementing strict hygiene measures, and monitoring flock health.” Furthermore, according to Eric Cardinale, “The capability of these viruses to evolve through genetic exchanges is significant, and while recent outbreaks in the U.S. exhibit heightened transmission risk, the ability to adapt to human hosts remains limited. Sustain surveillance and preparedness must remain paramount.”

Right now, the level of risk for human health remains low, and such transmission is extremely rare at a national level. Nevertheless, vigilance and early intervention are critical to mitigate any potential outbreaks.
– Eric Cardinale, in Influenza: Recent Developments and Implications

The CDC and other public health authorities emphasize the importance of vigilance and early intervention in managing potential outbreaks, ensuring that healthcare professionals and the public are well-informed and prepared to respond to any evolving threats.

Refer to our in-depth analysis on public health readiness and prevention strategies for a comprehensive understanding of current challenges and future preparedness in managing zoonotic flu outbreaks across the United States.