Avian influenza (sometimes called "bird flu") refers to influenza A viruses found in wild and domestic birds.
Birds transmit the viruses to other birds via infected respiratory
secretions and droppings.
Avian influenza strains are divided into to two categories based on
virus properties and the severity of disease seen in infected birds:
Low Pathogenic Avian Influenza (LPAI) infection in
birds causes no or mild disease. Indicators of LPAI in a flock
include ruffled feathers and a decrease in egg production. Because
the symptoms are mild, LPAI in a flock may not be detected. An
example of a well-known LPAI is
influenza A H7N9
identified in flocks in China.
High Pathogenic Avian Influenza (HPAI) infection in
birds can cause severe disease that is often fatal, especially in
poultry populations (chickens, turkeys, phesants). The disease is
often identified when disease or deaths in a flock or bird
population prompts testing. The most well-known HPAI strain is
influenza A H5N1 that has been seen in flocks in Asia and Europe.
Of note, the H5N1 virus recently identified in birds in the United States is
different than the Asian H5N1 virus
that has been identified in birds and, rarely, humans in contact
with birds for the last decade in Asia, Europe, and Africa.
Both LPAI and HPAI strains have been identified in birds throughout
Avian Influenza in People
Rarely, influenza in birds can be transmitted to humans. Both LPAI
and HPAI strains have been identified in humans. The vast majority
of people that have been found with to be sick with an avian
influenza virus have close contact with infected birds. Avian
influenza viruses do not transmit readily from person to person.
Only a small handful of person to person avian influenza
transmissions have ever been identified in people with
extremely close contact with another case. However, epidemiologists around the world
keep close watch on these infections in case an avian influenza
virus mutates and develops the ability to transmit readily between
human hosts. People have little or no immunity against the influenza
viruses that circulate among birds, so avian influenza that can be
transmitted readily from person to person could potentially cause an
High Pathogenic H5 Avian Influenza in the United States
Recently, several high pathogenic influenza A H5 strains have been
identified in birds in the United States, including in Minnesota and
South Dakota. These identifications
followed an increase in testing after HPAI A H5N2 was identified in
chickens and turkeys on a poultry farm in British Columbia, Canada.
On April 9th, the North Dakota Board of Animal Health
announced samples from a commercial turkey flock in Dickey
County had perliminarily tested positive for avian influenza A H5.
HPIA A H5N2 was then confirmed.
A Second outbreank in commerical turkeys was
confirmed on April 24th. No
elevated human health risk for the general population associated with these birds has been
identified. Transmission of avian influenza to humans is not common,
and H5N2 avian influenza transmitting to a human has never been
It is possible a very small number of sporadic cases in people who
have had direct contact with sick birds associated with this or
other avian influenza outbreaks happening in the United States may be identified. Because of this,
health care providers are advised to look out for avian influenza
infection in humans who are in contact with sick birds (see
recommendation below). However, it is important that the public
understands that this recommendation is designed to identify a very
low probability scenario.
In December of 2014 the state of Washington reported identifying
HPAI A H5N8 in a grayfalcon that had died after eating a wild duck.
This was followed by several additional identifications of HPAI in
the western United States: H5N2, H5N1, and more H5N8 have been identified in
states that include California, Idaho,
Oregon, Utah, Nevada and Washington.
All of these states that can be found within the
a path followed by migratory birds. In late February, a large
die-off of turkeys on a turkey farm in Pope County,
Minnesota promted testing. It was determined that the birds
were infected with H5N2. This is the first recent HPAI to be
identified in the
Flyway, a migratory flyway that does include airspace over parts
of North Dakota. Soon after, Missouri and
Arkansas also annouced
H5N2 had been identified at Turkey farms in their states. In mid
March, Kansas became the first state in the
to report avian influenza, this time in a backyard flock of chickens
and ducks. Soon after, Wyoming reported its first
Central Flyway case, this time finding H5N2 in a wild goose. This
was followed by H5N2 identifications in South Dakota
(commercial turkey farm), Montana (backyard flock),
North Dakota (commercial turkey farm),
Wisconsin (commercial turkey farm, backyard flock, wild
Iowa (commercial chicken farms), Kentucky
(wild bird) and Nebraska (commercial egg laying
opperation). Indiana announced in May that they had
identified H5N8 in a backyard block. This is the first
identification of H5N8 outside the west coast.
Recommendation for Health Care Providers:
Recommendations for North Dakota Providers are outlined
here. Currently, the Centers for Disease Control and Prevention (CDC)
recommends that avian influenza be considered by health care
professionals as a possible diagnosis in people with influenza-like
illness (ILI) that have had recent contact with sick or dead birds,
especially in areas where the virus has been identified. The North
Dakota Public Health Laboratory can test for avian influenza. Rapid
and commercial influenza tests (including RT-PCR) may not be able to identify influenza
in people infected with influenza A H5 viruses. For this reason,
these tests should not be relied to preliminarily
identify avian influenza strains in people. Additionally, people who
have been exposed to birds that have tested positive for avian
influenza A H5 virus should be monitored for ILI for 10 days.
Influenza antiviral prophylaxis should be also be considered for
people with an identified exposure. Please contact that North Dakota
department of health for dosing information. Extensive CDC guidance
on identification and testing for avian influenza for public health
and health care professionals can be found
here. Possible infection with
an avian influenza virus is immediately
reportable via phone call to the North Dakota Department of Health
Division of Disease control (701-328-2378).