Influenza (Avian) Flashcards
Is avian influenza a nationally notifiable disease?
Yes - urgent.
Also notifiable to WHO under NIR.
What is the public health priority of avian influenza?
Urgent - respond to cases immediately.
Refer to jurisdictional CDB within an hour and CDB to refer to National Incident Room.
What is the infectious agent of avian influenza?
Influenza A virus (H5N1)
H5N1 clade 2.3.4.4b is the current circulating strain of concern.
What are the two broad categories of avian influenza?
- Low pathogenicity (LPAI)
- High pathogenicity (HPAI)
H5N1 (HPAI) has caused seriously illness and deaths in humans in outbreaks in poultry overseas.
H7N9 (LPAI) has caused serious illness and deaths in China but not linked with clinical disease in birds.
Based on virulence in birds NOT humans.
Believed that human pandemic influenza strains could arise from AI viruses.
What are the reservoirs of avian influenza?
Waterbirds in general.
More specifically, Anseriformes (ducks, geese, swans) and Charadiiformes (shorebirds, waders, gulls).
However reasonable to assume all birds susceptible to avian influenza.
How is avian influenza transmitted?
Bird-to-bird - via saliva, nasal secretions, faeces. Faeces have high viral load. Waterbirds can directly or indirectly introduce AI to poultry via contaminated faeces or environments.
Bird-to-person - rare. Need very close contact. AI can survive on poultry products (blood, eggs) but no documented transmission from cooked products.
Human-to-human - very rare. Reported following prolonged, unprotected, close contact but inefficient and unsustained.
How is avian influenza transmitted?
Transmission to humans is rare:
* Close contact with infected animals
* Inhaling dust contaminated with excreta
* Possible transmission uncooked poultry (rare)
Transmission between humans is rare, inefficient and unsustained.
What are the clinical features of avian influenza in humans?
Spectrum:
* Asymptomatic
* Mild URTI
* ILI - fever, myalgia, arthralgia, coryza, cough, odynophagia
Other: conjunctivitis, GI sx, rapidly progressing pneumonia and ARDS with high CFR (H5N1, H7N7)
Who are high-risk groups for being infected with avian influenza?
Anyone with close contact with birds:
- Occupational - poultry workers, agricultural workers, wildlife handlers, vets, laboratory, people handling infected animal products
- First Nations - hunting
- Hunters
- Overseas travellers - contact with birds, mammals, human case
Who are at high risk of severe disease?
- Immunocompromised
- Pregnant/postpartum
- Children
- Elderly
- First Nations
What are the case definitions for avian influenza?
Confirmed - lab definitive (isolation/PCR/serology) AND clinical
Probable - lab suggestive + clinical + epi
How is avian influenza diagnosed?
NP, throat, conjunctival swabs.
- PCR for AI, viral culture
- Paired sera
Send to reference lab.
How are cases of avian influenza managed?
Single room (negative pressure of available). Treat with neuraminidase inhibitor within 48 hours of onset.
How are contacts of avian influenza managed?
Contacts of infected humans or birds must be rapidly identified, counselled on their risk, provided with neuraminidase inhibitor (if indicated) and placed under surveillance for 10 days after their exposure.
What is the incubation period for AI?
1-10 days depending on the strain. Typically longer than normal seasonal influenza (2-3 days)
What is the clinical presentation of avian influenza?
Depends on haemagglutinin subtypes. Flu-like symptoms in general but range from no symptoms to viral pneumonia, ARDS with high case-fatality ratio.
Who is at risk of avian influenza?
Close contact:
- overseas: infected material from birds or human case
- in Australia: contact with infected bird e.g. poultry worker
- laboratory worker
Public health significance of avian influenza
List outbreaks on bird farms and human cases
Routine prevention activities for avian influenza
- overseas travellers: hand hygiene, avoid close contacts with birds in countries where AI is enzootic
- good OHS for people working closely with birds
- communication and collaboration between jurisdictional agencies responsible for human and animal health
Risk mitigation for avian influenza
Biosecurity measures have been put in place however some premises (e.g. free range poultry farms) may be at increased risk of contamination from waterbirds.
Strict quarantine rules / inspections at seaports and airports.
AUSVETPLAN
Vaccination so that co-infection with seasonal influenza is less likely to occur - reduced likelihood for gene reassortment and pandemic influenza potential.
What isolation and restriction is required for cases of AI?
Cases must be isolated (single, negative pressure room if available) until no longer infectious. HCWs - airborne, droplet, contact, standard IPC precautions.
How are contacts of AI identified?
Human-to-human transmission is rare and probably requires close, prolonged contact. Case-by-case basis based on expert panel judgement.
How are contacts of a case managed?
Define contact explicitly. Experts - virology, animal health, influenza, poultry and influenza experts, IDP, PHU.
May require treatment with neuraminidase inhibitor.
No isolation/restriction but education and monitor during incubation period. 10 days daily monitoring.
How are cases managed?
Isolate until no longer infectious.
Single negative pressure room with airborne, droplet, contact and standard IPC precautions.
Treatment by clinician in consultation with expert in virology. Neuraminidase inhibitor e.g. oseltamivir.
