1. H7N9 Avian Influenza: What You Need to Know, Not Fear
Nathaniel L. Tablante, DVM, MPVM, MS, DACPV
Associate Professor and Extension Poultry Veterinarian
VA-MD Regional College of Veterinary Medicine
University of Maryland College Park
8075 Greenmead Drive
College Park, MD 20742
Tel
Fax

2. Outline Introduction Mutation and Reassortment
Avian influenza (AI): definition and classification
Sources of AI virus
Types of AI in domestic poultry
Incubation and survival of AI virus
Modes of transmission
Mutation and Reassortment
Antigenic Drift/Shift
Avian Influenza Infections in Humans
Flu Pandemics
Prevention of AI in Humans

3. What is Avian Influenza (AI)?
Avian influenza (AI) is an infectious, viral disease of birds caused by several subtypes of the type A strain of the influenza virus
Avian influenza viruses usually do not infect humans but several cases of human infection have been reported since 1997

4. Influenza A virus host range is polygenic
a2-6Gal
a2-3Gal
a2-3Gal
big part of surveillance is made in wild aquatic birds
-aquatic birds are natural reservoir.
a2-6Gal
a2-3Gal
a2-6Gal
(Perez, 2006)

5. Classification
Influenza viruses are subtyped according to surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA)
Currently, there are 16 hemagglutinins (H1 to H16) and 9 neuraminidases (N1 to N9)
144 possible sub-types
Hemagglutinin attaches the virus to the surface of the host cell so the virus can replicate
Neuraminidase lets the newly replicated viruses out of the cell to infect more cells

6. Where does AI virus come from?
All known subtypes of influenza A viruses circulate among wild birds, especially migratory waterfowl (e.g. ducks and geese) which are considered natural reservoirs for influenza A viruses
Domestic poultry like chickens and turkeys are not natural reservoirs for AI virus and usually develop clinical disease when infected with AI virus

7. What are the types of Avian Influenza in domestic poultry?
Low pathogenic avian influenza (LPAI)
mild or no clinical signs
low to moderate mortality
However, the low pathogenic H5 and H7 strains are capable of mutating under field conditions into highly pathogenic strains
Highly pathogenic avian influenza (HPAI)
sudden onset
severe clinical signs
high mortality

8. Low Pathogenic AI
Highly Pathogenic AI

9. What is the incubation period?
Usually 3 to 7 days
Depends on:
strain of virus
dose of inoculum
age and immune status of bird
management and environmental factors

10. How long can AI virus survive?
AI virus is shed in feces for 7 to 14 days after infection
AI virus can survive in manure for up to 105 days especially with high moisture and low temperature
1 gram of contaminated manure can infect 1 million birds
1 gram of manure will cover the surface of a dime

11. How does AI virus spread?
Exposure of poultry to migratory waterfowl

12. How does AI virus spread?
Exposure of commercial poultry to AI-infected backyard, gamebird, or hobby flocks

13. How does AI virus spread?
Contact with AI-infected live bird markets
Dr. S. Trock
Dr. S. Trock

14. How does AI virus spread?
Bird to bird contact (through feces)
Aerosol droplets

15. How does AI virus spread?
Manure, equipment, vehicles, egg flats, crates, contaminated shoes and clothing

16. How does AI virus spread?
Wildlife vectors/scavengers
Photos courtesy of G. Malone University of Delaware

17. How do humans get infected with H7N9?
Mainly through direct contact with infected poultry
When people sell or slaughter and consume infected birds
Exposure during slaughter, defeathering, butchering, and preparation of poultry for cooking
So far, evidence suggests that the source of H7N9 virus is poultry and live bird markets and the most likely route of transmission from poultry to humans

18. Why should we be concerned about H7N9?
H7N9 has not been previously reported in humans
No background or pre-existing immunity
H7N9 is more easily transmissible from poultry to humans than H5N1
However, unlike H5N1 infections, poultry infected with H7N9 appear healthy

19. How do AI viruses change or mutate?
Antigenic Drift
Occurs through small changes in the virus that happen continually over time
Produces new virus strains that may not be recognized by antibodies to earlier influenza strains
Antigenic Shift
An abrupt, major change in influenza A viruses, resulting in a new influenza virus that can infect humans (one that has not been seen in humans for many years)

20. Mutation and Reassortment 1
AVIAN
virus
HUMAN
virus
2. Reassortment
Reassortant
HUMAN- AVIAN virus
Dr. R. Schieber, CDC

21. Mutation and Reassortment 2
AVIAN
virus
HUMAN
virus
2. Reassortment
Reassortant
HUMAN- AVIAN virus
Dr. R. Schieber, CDC

22. Can H7N9 spread from person to person?
Avian flu
Human flu
The spread of infection in birds increases the opportunities for direct infection of humans
Humans concurrently infected with human and avian influenza strains could serve as a “mixing vessel” for the emergence of a novel subtype with sufficient humans genes that can be transmitted from person to person
However, the virus has not yet developed the ability to pass easily from human to human
Novel flu subtype

23. Avian Influenza Infections in Humans
1997: Hong Kong (HPAI H5N1)
Infected chickens and humans
18 sick (6 died)
Spread primarily from birds to humans
Person-to-person infection noted but rare
1.5 million chickens destroyed
yaleglobal online

24. Avian Influenza Infections in Humans
2003: China and Hong Kong (HPAI H5N1)
Occurred among members of a Hong Kong family that had traveled to China
1 person recovered, another died
Another family member in China died
Origin unknown

25. Avian Influenza Infections in Humans
2003: Netherlands (HPAI H7N7)
Occurred among poultry workers and their families during an AI outbreak in poultry
89 cases reported (mostly conjunctivitis and some respiratory signs)
1 veterinarian died from acute respiratory infection
Most cases occurred due to direct contact with infected poultry

26. Avian Influenza Infections in Humans
2013: China (H7N9)
126 cases (24 deaths) as of 29 April 2013
ecdc.europa.eu

27. Pandemics are rare but deadly
Spanish Flu (H1N1)
20-50 million infected worldwide
>500,000 deaths U.S.
Asian Flu (H2N2)
70,000 deaths U.S.
Hong Kong Flu (H3N2)
50,000 deaths U.S.
Swine Flu (H1N1)
60 million infected worldwide
18,000 deaths

28. Can another pandemic happen again?
Only when three conditions have been met:
a new influenza virus subtype emerges
it infects humans, causing serious illness
it spreads easily and sustainably among humans*
*has not yet occurred with H7N9 or H5N1

29. What can we do to prevent AI in humans?
Practice normal hygienic precautions
Wash hands with soap and water for seconds
Cover your mouth when you cough or sneeze
Get vaccinated for seasonal flu
Stay home and rest if you have the flu
Practice “social distancing” if there is a flu outbreak
Avoid live bird markets

30. Questions?