There has been growing concern recently over reports of a new bird virus detected in Florida. Avian influenza viruses are constantly circulating in wild bird populations, and there is heightened monitoring for the emergence of highly pathogenic strains that can cause outbreaks in domestic poultry. At this time, a low pathogenic H5N1 avian influenza virus has been confirmed in a single blue jay found dead in Palm Beach County, Florida. While this strain poses little risk to humans, further monitoring and surveillance is underway to determine if the virus is spreading among wild or domestic bird populations in Florida.
Background on Avian Influenza
Avian influenza refers to infection with any of the influenza type A viruses that commonly infect wild birds and poultry. Many different subtypes of avian influenza viruses exist, classified according to the combinations of two main proteins found on the virus surface, hemagglutinin (H) and neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes, allowing for new viral variants to emerge through reassortment of these segments.
Low Pathogenic vs High Pathogenic Strains
Avian influenza viruses are further categorized based on their virulence or ability to produce disease:
- Low pathogenic avian influenza (LPAI) causes little to no clinical signs of illness in infected birds
- High pathogenic avian influenza (HPAI) causes severe disease with high mortality rates in poultry flocks
HPAI strains are extremely infectious and fatal to chickens, with a mortality rate over 90% in just a few days. LPAI strains pose little threat to human health but can evolve into HPAI strains.
Host Species and Transmission
Wild aquatic birds, especially waterfowl and shorebirds, are the natural reservoir hosts for avian influenza viruses. In these species, LPAI viruses cause asymptomatic intestinal infections and are shed in the feces. Transmission occurs through direct contact with secretions or excretions of infected birds.
Domestic poultry, including chickens and turkeys, are particularly susceptible to avian influenza. Contact with infected migratory wild birds or their feces/secretions leads to transmission of the viruses to domestic flocks. Transmission between poultry occurs rapidly on farms and live bird markets.
H5N1 Avian Influenza
The H5N1 strain of highly pathogenic avian influenza first emerged in southern China in 1996 and has persisted in poultry across Eurasia and parts of Africa. The H5N1 virus likely emerged from reassortment between viruses found in wild ducks and geese and viruses adapted to infect domestic chickens.
Geographic Distribution
Between 2003-2007, H5N1 caused large outbreaks in domestic poultry and wild birds in over 60 countries across Asia, Europe, the Middle East, and Africa. Since 2015, the virus has been detected in wild birds and poultry in over 40 countries. Currently, H5N1 is considered endemic in poultry in several countries including China, Egypt, Indonesia, Cambodia, and Bangladesh.
Human Infections
While H5N1 does not usually infect humans, rare cases have occurred through close contact with infected birds. Since 2003, there have been over 800 confirmed human cases of H5N1 reported to the World Health Organization from 19 countries. Approximately 50% of those cases were fatal. However, to date no sustained human-to-human transmission has occurred outside of rare, non-sustained clusters.
Clinical Signs in Birds
H5N1 causes severe disease in domestic poultry. In chickens and turkeys, common symptoms include:
- Sudden death
- Lack of energy
- Decreased appetite
- Decreased egg production
- Soft-shelled or misshapen eggs
- Swelling of head, eyelids, comb, wattles, and hocks
- Purple discoloration of wattles, comb, and legs
- Difficulty breathing
- Nasal discharge
- Coughing, sneezing
- Lack of coordination
- Diarrhea
Mortality rates approach 100% in chickens and turkeys once clinical signs appear. In ducks, infection is typically mild or asymptomatic.
2022-2023 H5N1 Detection in Florida
In January 2022, H5N1 was detected in a wild American wigeon duck in Colleton County, South Carolina. This marked the first identification of H5N1 in the United States since 2016. The virus was determined to belong to the H5N1 2.3.4.4b clade, a variant that has been spreading globally since 2020.
In early 2022 and again in late 2022, additional H5N1 outbreaks occurred in wild birds and domestic poultry flocks in Canada, and the virus continued spreading throughout wild bird populations along Atlantic migratory flyways.
Palm Beach County Blue Jay
On January 27, 2023, the Florida Fish and Wildlife Conservation Commission announced detection of H5N1 in a blue jay found dead in Palm Beach County. Diagnostic testing at the University of Georgia Southeastern Cooperative Wildlife Disease Study confirmed the presence of a low pathogenic H5N1 avian influenza virus.
This is the first reported case of H5N1 in Florida. The blue jay is a peridomestic species that often visits backyard bird feeders, so transmission likely occurred from contact with wild waterfowl. Officials believe this was an isolated case, but are actively monitoring for additional cases.
Ongoing Surveillance in Florida
Florida has an extensive avian influenza surveillance program in place for commercial poultry operations. Samples are regularly collected from flocks and sent for testing at the Bronson Animal Disease Diagnostic Laboratory.
Enhanced monitoring of wild bird mortality events is also ongoing. The Florida Fish and Wildlife Conservation Commission is urging the public to report any sightings of sick or dead wild birds at www.MyFWC.com/bird. Dead birds should not be handled barehanded.
Risks to Humans
Avian influenza viruses in the wild pose little threat to humans. Rare cases of human infection with H5N1 have almost always occurred from direct or close contact with infected poultry. There has never been an H5N1 human case identified in the United States.
Human infections with H5N1 cause typical flu-like symptoms including fever, cough, sore throat, muscle aches. Unlike seasonal flu, viral pneumonia and ARDS often develop, and the lower respiratory tract is affected more than the upper. The mortality rate for human H5N1 cases has been around 50% when antiviral treatment is unavailable.
Precautions for Humans
The CDC considers the current risk to the general public’s health in the US to be low. As a precaution, the following guidance is provided:
- Avoid direct contact with wild birds and poultry that appear ill or have died
- Do not touch sick or dead wild birds or poultry with bare hands. Use disposable gloves or inverted bags to dispose of carcasses
- Clean hands and change clothing after exposure to birds
- Do not eat undercooked or raw poultry products
- Report unusual public bird deaths online at www.MyFWC.com/bird
There are no commercial poultry impacts at this time and poultry remains safe to eat if properly handled and cooked. There is no risk consuming properly cooked eggs or poultry products.
Conclusion
The recent detection of low pathogenic H5N1 in a Florida blue jay marks the virus’ first recorded appearance in the state. While concerning, avian influenza is endemic in wild birds and periodic spillover events in local populations are not unexpected. Surveillance programs are actively monitoring for any indications that the virus is spreading further in wild or domestic flocks regionally. The current risk to public health remains very low, but guidance is provided to minimize any possible exposures when handling birds. With continued vigilance and reporting of wild bird mortality events, officials can stay ahead of any potential avian influenza emergence in Florida.
