What is avian pneumonia also known as?

Avian pneumonia, also known as bird flu, is a contagious respiratory disease caused by influenza viruses that primarily infect birds such as chickens, turkeys, ducks, and geese. However, some strains are known to infect and cause illness in other species, including humans.

Common Names for Avian Pneumonia

Avian pneumonia is most commonly referred to as:

• Bird flu
• Avian influenza
• Fowl plague

Some specific strains of avian pneumonia may also be referred to by their alphanumeric designations, such as:

• H5N1 – A highly pathogenic strain that has caused outbreaks in poultry and some human infections
• H7N9 – A low pathogenic strain that has caused human infections in China
• H5N8 – A highly pathogenic strain that has caused recent outbreaks in Europe and Asia

Key Facts About Avian Pneumonia

Here are some key facts about avian pneumonia:

• Caused by Type A influenza viruses that normally infect wild birds such as waterfowl
• Transmitted through contact with nasal and respiratory secretions and feces of infected birds
• Signs in birds include decreased food/water intake, nasal discharge, coughing, difficulty breathing
• Some strains like H5N1 are highly pathogenic, causing severe illness and high mortality in poultry
• Other strains like H7N9 are low pathogenic, causing milder illness in poultry
• Human infections are rare but can occur through close contact with infected birds/environments
• Human symptoms include fever, cough, sore throat, muscle aches, eye infections, pneumonia
• About 60% of human cases have resulted in death

History and Evolution

Avian pneumonia has likely existed in wild waterfowl populations for millennia. However, more pathogenic strains evolved in the late 1990s and early 2000s, causing larger outbreaks in poultry and transmission to humans.

• 1996 – H5N1 emerges in China, causing a poultry outbreak in Guangdong Province
• 1997 – First reported human H5N1 infection documented in Hong Kong
• 2003 – Reemergence and spread of H5N1 across Asia to Europe and Africa
• 2013 – H7N9 emerges and causes human infections in China
• 2014 – H5N8 detected and causes outbreaks in Europe and Asia
• 2016 – H5N8 introduces to North America

These more recent epidemics and panzootics highlight the ability of avian influenza viruses to mutate and spread rapidly between wild birds, poultry flocks, mammals like minks, and humans.

Geographic Distribution and Host Range

Avian influenza viruses naturally circulate among wild waterfowl populations globally but can infect various hosts:

Major geographic hotspots for avian influenza emergence and spread include:

• Eastern and Southeastern Asia (China, Vietnam, Indonesia)
• Egypt
• West Africa
• Eastern Europe

Transmission

Avian influenza viruses spread between birds via:

• Direct contact with infected birds
• Contact with nasal/respiratory secretions or feces
• Contact with contaminated surfaces like cages or water
• Aerosolized respiratory droplets dispersed by wind
• Fomites like equipment, vehicles, clothing, boots

For strains that can infect mammals like H5N1, additional routes include:

• Consumption of uncooked poultry products
• Swine consuming uncooked infected poultry carcasses
• Wild birds to domestic poultry when raised outdoors
• Markets selling diverse live poultry and mammalian species

Signs and Symptoms in Birds

In poultry and wild birds, signs of avian pneumonia include:

• Sudden death
• Decreased appetite, food and water intake
• Depression, decreased activity
• Drop in egg production
• Soft-shelled or misshapen eggs
• Nasal discharge
• Swelling and purple discoloration of head, comb, wattles
• Coughing, sneezing, difficulty breathing
• Diarrhea
• Tremors, circling, incoordination, paralysis
• Vomiting, blood-tinged oral discharge

Signs and Symptoms in Humans

In humans, common symptoms of avian influenza include:

• Fever > 100.4°F (38°C)
• Cough
• Sore throat
• Muscle and joint pain
• Severe respiratory illness (pneumonia, ARDS)
• Eye infections (conjunctivitis)
• Nausea, vomiting, diarrhea (more common in children)

In severe cases, complications can include respiratory failure, septic shock, organ failure, and death. Those at highest risk include older adults, very young children, and those with underlying medical conditions.

Diagnosis

Avian influenza is diagnosed through:

• Clinical signs and symptoms: Sudden onset of fever and respiratory illness in areas with known outbreaks increases suspicion.
• Imaging: Chest X-ray or CT scan may show pneumonia or ARDS pattern.
• Lab tests: RT-PCR testing of respiratory samples detects influenza RNA. Viral culture or antigen detection may also be used.
• Serology: Paired acute/convalescent serologic testing looks for a rise in influenza antibodies.

Treatment

Most avian influenza treatment is supportive, aimed at relieving symptoms and preventing complications. Key measures include:

• Rest and hydration
• Fever control with acetaminophen
• Treatment of associated pneumonia with antimicrobials, oxygen support
• ICU care for respiratory failure, shock

Antiviral drugs like oseltamivir may reduce severity if started early in illness. Corticosteroids are controversial due to concerns about viral replication.

Prevention and Control

Preventing avian influenza relies on measures like:

• Culling infected poultry flocks
• Restricting movement in/out of hot zones
• Enhanced biosecurity on farms – disinfection, protective clothing, separating flocks
• Market regulation and surveillance – testing, no live bird sales
• Wild bird monitoring via sampling/tracking
• Public education on risk factors and prevention
• Pandemic preparedness plans
• Vaccines in poultry, humans

Conclusion

Avian pneumonia or bird flu refers to contagious respiratory disease from avian influenza viruses that primarily infects birds but can spread to mammals. Major outbreaks in poultry and human cases highlight the public health threat of highly pathogenic strains like H5N1 and H7N9. Controlling avian pneumonia relies on surveillance, biosecurity, and pandemic preparedness across human, animal, and environmental health sectors.