Latest Virus Alerts: Highly Pathogenic Avian Influenza (HPAI) Updates

Highly Pathogenic Avian Influenza (HPAI), a severe form of bird flu caused by H5 and H7 avian influenza A viruses, poses a significant threat to poultry, causing high mortality rates among infected birds . While human infections with HPAI viruses are rare, sporadic cases have raised concerns about the potential health risks, emphasizing the importance of vigilance and prevention measures

As HPAI can spread via wild birds to domestic poultry and other animals, understanding its transmission dynamics is crucial for controlling outbreaks . The article will discuss the spread and impact of HPAI on poultry and livestock, human health risks, and outline current prevention and control strategies alongside ongoing research developments.

Spread and Impact on Poultry and Livestock

Timeline of HPAI Spread in the U.S.

1.       Initial Detection in Wild Birds

·         HPAI was first detected in wild waterfowl along the Atlantic flyways in January 2022

2.       Spread to Commercial Poultry

·         The first confirmed case in a commercial setting occurred in Texas on April 2, 2022, within a chicken flock

3.       Impact on Wild and Domestic Birds

·         As of 2024, over 9,200 wild birds across 50 states and more than 1,100 commercial and backyard flocks in 48 states have been affected, totaling over 90 million birds

Economic and Ecological Impact

    ·         Poultry Industry Threat

·         Avian influenza poses a significant threat to the poultry industry, impacting trade and the economy globally

·         In 2023, the U.S. processed over 9.4 billion broiler chickens and 218 million turkeys, highlighting the industry's vast scale and the potential for substantial economic loss

    ·         Global Outbreaks

·         In 2022, 67 countries reported H5N1 outbreaks, with over 131 million domestic poultry lost due to death or culling ^{[9] https://www.who.int/news/item/12-07-2023-ongoing-avian-influenza-outbreaks-in-animals-pose-risk-to-humans}.

·         The following year, 14 additional countries reported outbreaks, mainly in the Americas, signifying a persistent and spreading threat

Transmission and Biosecurity

    ·         Routes of Transmission

·         The virus spreads through direct bird-to-bird contact and via contaminated surfaces

·         Notably, in 2024, HPAI A(H5N1) spread among dairy cattle in multiple U.S. states, with investigations into farm-to-farm transmission ongoing

    ·         Biosecurity Measures

·         Strong biosecurity practices are crucial to prevent the spread of the virus from wildlife to domestic birds and among farms

·         There is no treatment for HPAI; the primary control method is depopulating affected and exposed poultry

Impact on Other Species

   ·         Sporadic Infections in Mammals

·         There have been reports of HPAI infections in various mammals, including polar bears, minks, foxes, seals, goats, and domestic pets

·         At least 26 species of mammals have been affected by HPAI, indicating the virus's potential to cross species barriers

This section outlines the significant spread and impact of HPAI on poultry and livestock, emphasizing the urgency for stringent biosecurity measures and ongoing vigilance.

Human Infections and Health Risks

Overview of Human Infections

Human infections with Highly Pathogenic Avian Influenza (HPAI) A(H5N1) remain rare, with the CDC emphasizing a low risk to the public, primarily affecting those in direct contact with infected birds or environments . From January 2022 through April 2024, 26 sporadic human cases were reported globally, underscoring the necessity for caution and awareness

Transmission Dynamics

·         Direct Contact: The primary mode of transmission to humans involves direct interaction with infected poultry or their bodily excretions

·         Aerosol Transmission: Inhalation of contaminated droplets or dust can also facilitate virus transmission .

Clinical Presentation and Outcomes

·         Symptoms: Infected individuals may experience a range of symptoms from mild respiratory issues to severe conditions including shortness of breath, muscle aches, and in some cases, gastrointestinal symptoms

·         Case Severity: Of the reported cases, several have been severe or critical, with a notable mortality rate, highlighting the potential severity of the disease

Risk Factors and Prevention

·         High-Risk Groups: Individuals with occupational or recreational exposure to birds are at heightened risk. This includes poultry workers and wildlife rehabilitators

·         Preventive Measures: The CDC recommends prompt antiviral treatment for suspected cases and stringent biosecurity measures to mitigate virus spread

Genetic Insights and Implications

Research indicates that HPAI A(H5N1) can undergo genetic changes in mammals, potentially enhancing its ability to replicate in human tissues, which could influence future virus behavior and cross-species transmission

Prevention and Control Measures

Biosecurity Protocols and Practices

4.       Surveillance and Testing: Federal and state partners are actively conducting additional surveillance and testing in areas affected by HPAI

5.       Biosecurity Education: Comprehensive biosecurity tips are available on the Commercial Poultry Biosecurity Page and Backyard Biosecurity Page to prevent contact between domestic poultry and wild avian species

6.       Personal Protective Equipment: Use of gloves, N95 respirators, or well-fitting facemasks, and eye protection is recommended when handling birds

7.       Hygiene Practices: Regular hand washing with soap and water after touching birds or their environments is crucial

8.       Cooking Guidelines: Poultry and eggs should be cooked to an internal temperature of 165˚F to kill viruses and bacteria

Environmental Management and Isolation Practices

·         Wildlife Control: Keeping wild birds away from domestic birds and avoiding contact with wild birds and domestic poultry, especially those appearing sick or deceased

·         Cage and Equipment Sanitation: Daily changing of food and water, regular disinfecting of cages and equipment, and proper disposal of dead birds are essential

·         Isolation of New Birds: New birds should be quarantined from the rest of the flock for at least 30 days to monitor for signs of disease

·         Visitor Restrictions: Limiting farm access to employees and essential personnel only to prevent disease spread

Monitoring and Response

·         Health Monitoring: CDC and local public health partners monitor individuals in the U.S. who have been exposed to infected birds for signs of infection .

·         Vaccine Development: H5 candidate vaccine viruses developed by the CDC are expected to provide protection against current HPAI A(H5N1) strains .

·         Outbreak Response: In the event of exposure, it is advised to isolate, seek medical testing, and report symptoms to a healthcare provider

International and Intersectoral Cooperation

·         Tripartite Collaboration: The FAO, WHO, and WOAH emphasize the importance of preventing avian influenza at its source, enhancing surveillance, and ensuring rapid response to outbreaks

Ongoing Research and Developments

FDA Milk Study and Viral Assessments

9.       National Commercial Milk Sampling: The FDA's ongoing national study involves sampling commercial milk to evaluate pasteurization effectiveness against HPAI, revealing that approximately 20% of retail samples were qPCR-positive for HPAI viral fragments .

10.   Egg Inoculation Tests: Following the initial qPCR tests, the FDA conducts egg inoculation tests to determine the presence of infectious viruses, ensuring the safety of the milk supply

Genetic Diversification and Surveillance

·         HPAI A(H5N1) Genetic Evolution: Since 2005, HPAI A(H5N1) viruses have diversified genetically, resulting in hundreds of new genotypes through reassortment with other avian viruses, highlighting the dynamic nature of this virus

·         CDC's Active Monitoring : The CDC is closely monitoring clade 2.3.4.4b HPAI A(H5N1) viruses, particularly concerning their spread in wild birds and potential infections in mammals .

International Research on HPAI

·         South American Studies: Recent studies in South America have isolated and characterized genomes of HPAIV H5N1 clade 2.3.4.4b, linking them to North American strains and indicating local viral evolution

·         Importance of Wild Birds: Research underscores the role of migratory birds, especially Anseriformes and Charadriiformes, in the spread and emergence of novel HPAI viruses, necessitating ongoing genomic surveillance.

Research on Mammalian Transmission

·         Potential for Increased Spread: Ongoing studies aim to identify genetic changes in the HPAI virus that could facilitate easier transmission among mammals, including humans, which could significantly impact public health strategies

FAQs

1. Can humans contract HPAI ?Yes, HPAI viruses, primarily spread by wild birds to domestic poultry and other birds and animals, can occasionally infect humans. It's crucial to understand that the term "highly pathogenic" primarily describes the severity of the disease in birds rather than in humans, although human infections have been reported sporadically.

2. What strain of HPAI is currently prevalent?The current strain causing concern is the Eurasian H5 strain of highly pathogenic avian influenza (HPAI). It has been detected in both wild birds and domestic poultry across the United States. Poultry owners are advised to enhance their biosecurity measures and remain alert to prevent the disease from spreading to their birds.

3. Is there an ongoing avian flu outbreak?Yes, there is an ongoing outbreak of HPAI, particularly noted in Marin, Merced, and Sonoma counties. This nationwide outbreak began in 2022. Detailed information and updates on all detections can be found on the USDA website under the section "2022-2023 Detections of Highly Pathogenic Avian Influenza."

4. What are the symptoms of bird flu in humans as of 2024?In humans, the symptoms of bird flu or avian influenza can include a sore throat, cough, fever, runny or stuffy nose, headache, muscle or body aches, fatigue, and shortness of breath. Less frequently, infected individuals might experience nausea, vomiting, diarrhea, and seizures.