United States Department of Agriculture

Animal and Plant Health Inspection Service

July 25, 2019

Key Points

There are two non-H5/H7 avian influenza viruses 

currently circulating outside the United States which 

pose a potential risk to U.S. poultry. One is a poultryadapted H9N2 virus from Asia, and the other is a 

European wild bird origin H3N1 virus infecting poultry. 

Both lineages are categorized as low pathogenicity, per 

the testing prescribed by OIE, and neither are 

internationally reportable; however, each have been 

reported to have become poultry-adapted, causing 

increased morbidity and mortality in poultry. 

The Eurasia H9N2 infection has been linked to human 

illnesses. Additional information on influenza viruses 

communicable to humans is available from the Centers 

for Disease Control and Prevention.

Poultry-adapted H9N2

• This virus has been endemic among poultry in Asia 

since the early 2000’s and has spread to poultry in 

other countries, becoming endemic in the Middle 

East and Africa. In the past year, Russia has also 

reported the virus. 

• There are several lineages of this poultry-adapted 

virus which have become endemic among poultry in 

some countries and some caused human 

infections.3, 8

• Although the H9N2 subtype has sporadically been 

reported in U.S. poultry, these detections represent 

North American wild bird lineage viruses and are 

readily distinguishable from the poultry-adapted 

Asian H9N2 lineage.

Wild bird origin H3N1 in Europe

• The H3N1 virus was recently detected by animal 

health officials in Belgium and France, and the initial 

introduction of the virus was likely from a wild bird 

source. As with the H9N2 above, this virus is readily 

distinguishable from North American H3 viruses. 

• Between April 6 and July 4, 2019, the Belgium 

Federal Agency for the Safety of the Food 

Chain (FASFC) detected H3N1 virus on poultry 

farms (primarily laying hens and broiler 

breeders). Some flocks experienced production 

drops of up to 100 percent and mortality rates 

up to 60 percent. However, at least one infected 

flock showed no clinical signs; the potential of 

cofactor/co-infection involvement in flocks 

experiencing high morbidity/mortality is being 

investigated.6

• In the north of France, about 5 miles from the 

Belgium border, three epidemiologically-linked 

poultry flocks were also reported in May 2019 to 

be infected with H3N1. The outbreaks had 

similar production losses and mortality as those 

observed in Belgium.4

• With the increased morbidity and mortality 

associated with H3N1 infection, Belgium sought 

permission from the European Commission to 

cull birds and provide compensation, a measure 

usually reserved for outbreaks of highly 

pathogenic avian influenza.5

Concerns for US Animal Health

• The current risk of introduction of the H9N2 or 

H3N1 viruses to U.S. poultry through imports of 

live birds or products is considered low when 

U.S. import requirements are followed. 

• Illegal importation of infected poultry or poultry 

products represents the greatest risk for 

introduction of the poultry-adapted lineages of 

H9N2 virus into the U.S.

• As a wild bird origin virus, the H3N1 could 

potentially reach the U.S. via intercontinental 

migratory bird movements.1, 2 Poultry production 

premises vulnerable to wild bird contacts are at 

greater risk.7

• Early notification and response are essential to 

prevent serious impacts to U.S. poultry. 

Emerging Risk Notice

October 2019

H9N2 and H3N1 

Avian influenza viruses
United States Department of Agriculture

Animal and Plant Health Inspection Service

Epidemiology

• In chickens and turkeys, clinical signs may include 

mild respiratory disease (noise, swollen faces, 

conjunctivitis). In breeders, it can also cause a 

production drop, and birds may produce soft 

shelled eggs. With severe variants of the avian 

influenza viruses, the birds may become very quiet, 

not eat or drink, have diarrhea, and discolored 

combs and feet. Birds may also die suddenly 

without any signs of disease.

• Although it is possible for domestic poultry to 

become infected with avian influenza from direct 

contact with wild birds, it is more likely that avian 

influenza viruses are spread indirectly to poultry on 

contaminated feed, clothing, and equipment.

• Avian influenza subtypes H5 and H7 viruses are 

reportable regardless of pathogenicity; however, 

avian influenza of other subtypes are not 

internationally reportable, and as with the lineages 

of H9N2 and H3N1 presented in this Notice, may 

enter the poultry sector and spread, causing 

significant morbidity and mortality. If this occurs, 

investigation and testing is necessary to identify 

the cause of the change in health status of the 

flock with differential diagnoses including avian 

influenza. 

Diagnostic Testing

• In the U.S., avian influenza surveillance testing is 

designed to detect influenza A, and the 

laboratories that conduct official testing [the 

National Animal Health Laboratory Network 

(NAHLN) and the National Poultry Improvement 

Program (NPIP) laboratories] are obliged to 

forward any influenza A or antibody detection to 

the National Veterinary Services Laboratories 

(NVSL) for further characterization, which includes 

sequence determination of subtype as well as 

lineage.

• It is of critical importance to promptly notify the 

State or Federal Animal Health Official when 

unexplained high morbidity and mortality are 

present in poultry. A Foreign Animal Disease 

Investigation (FADI) may be initiated to include 

required sample collection and submission for 

avian influenza testing. (9CFR 145.15) (FADI). 

Refer to Avian Sample Collection for Influenza A 

and Newcastle Disease.

Treatment

• Avian influenza vaccines can prevent clinical 

signs and death in poultry and may reduce viral 

replication and shedding from the respiratory 

and GI tracts.9 Available licensed vaccines are 

likely poor antigenic matches to the H3N1 and 

H9N2 poultry-adapted AI strains, and will 

provide suboptimal performance. Licensed AI 

vaccine may only be used as part of an official 

USDA animal disease control program.

Prevention

• Producers are encouraged to prevent wild birds 

and other wildlife from coming into direct 

contact with their poultry, and to avoid 

transporting wild bird fecal material and 

secretions to poultry via boots, equipment, and 

feed.10

• Improving biosecurity is an effective strategy to 

reduce the risk of introduction and spread of 

avian influenza in the U.S. (NPIP Biosecurity 

Principles and What Poultry Growers need to 

Know)

• For early detection, notify your State and 

Federal Animal Health authorities if changes in 

your poultry’s health status, such as those 

noted below, occur at the house level:

o There is a reduction of more than 20% in 

water and food consumption;

o The mortality rate is more than 3% per 

week;

o Egg production falls more than 5% for more 

than two days;

o Clinical signs or lesions suggesting the 

presence of avian influenza are found during 

post-mortem examination
United States Department of Agriculture

Animal and Plant Health Inspection Service

Sources

1. Lee D-H, et. al. Intercontinental Spread of AsianOrigin H5N8 to North America through Beringia 

by Migratory Birds. J Virol. 89(12):6521-6524. 

June 2015.

2. Dusek RJ, et. al. North Atlantic Migratory Bird 

Flyways Provide Routes for Intercontinental 

Movement of Avian Influenza Viruses. PLoS 

One. 9(3):e92075. March 19, 2014

3. Peacock TP, et. al. A Global Perspective on H9N2 

Avian Influenza Virus. Viruses 2019, 11, 620; 

doi:10.3390/v11070620

4. Plateforme Epidemiosurveillance sante animale 

(ESA). France. H3N1 outbreaks in France 

(North) and Belgium: Situation as of June 14, 

2019. https://www.plateforme-esa.fr/...francenord-et-en-belgique-situation-au-14-juin-2019

5. USDA Foreign Agricultural Service (FAS) Global 

Agricultural Information Network (GAIN) Report 

Number BE1903 – Belgium-Luxembourg. 

Belgian Avian Influenza H3N1 Outbreak Shows 

High-pathogenic Behavior. 19 June 2019. 

https://gain.fas.usda.gov/.../Belgian...H3N1 

Outbreak...pdf

6. Federal Agency for the Safety of the Food Chain 

(FASFC). Avian Flu. Infections with the type H3 virus. 

July 11, 2019. http://www.favvafsca.be/santeanimale/h3/h3.asp

7. Lei Li, et. al. Genetic Evidence Supports Sporadic and 

Independent Introductions of Subtype H5 LowPathogenic Avian Influenza A Viruses from Wild Birds 

to Domestic Poultry in North America. Journal of 

Virology Sep 2018, 92 (19) e00913-18; DOI:

10.1128/JVI.00913-18

8. Pusch EA, Suarez DL. The Multifaceted Zoonotic Risk 

of H9N2 Avian Influenza. Vet. Sci. 5:82. 2018. 

doi:10.3390/vetsci5040082

9. World Organization for Animal Health (OIE) Terrestrial 

Manual - 2018. Chapter 3.3.4. Avian Influenza. 

www.oie.oint/...standards/...AI.pdf

10. US Geological Survey. Can Wild Birds Spread Avian 

Influenza to Poultry? Pulled on August 12, 2019. 

https://www.usgs.gov/faqs/...

Prepared by:

Sherrilyn Wainwright, DVM, MPH

USDA APHIS VS CEAH Risk Identification Team

With collaboration of USDA APHIS IS, NVSL, and Poultry 

Staff

For further information contact:

Dana Cole, DVM, PhD 

Risk Identification & Risk Assessment Director.

USDA APHIS VS CEAH 

E-mail: Dana.J.Cole@usda.gov