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Emergency: requires immediate attention
Avian influenza
Other Resources UpToDate PubMed
Emergency: requires immediate attention

Avian influenza

Contributors: Neil Mendoza MD, Paritosh Prasad MD
Other Resources UpToDate PubMed

Synopsis

Avian influenza viruses (also known as avian flu and bird flu) are influenza A viruses that are generally found in the intestines of wild birds.

Migratory wild birds, asymptomatic carriers of the virus, can infect domestic birds such as chickens, ducks, and turkeys. Infection makes the domestic birds sick, and most die.

Humans acquire avian influenza viruses primarily through direct contact of the mucous membranes with infectious secretions and excreta from infected birds or contaminated poultry products. The major portal of entry appears to be the upper respiratory tract. Although human-to-human transmission has been suggested in several household clusters, so far, there has been no sustained human-to-human transmission. Much remains to be learned about the exact mode of transmission. Most human illness from avian influenza has resulted from infection with Asian lineage H7N9 and H5N1 viruses. A man in China was hospitalized in May 2021 with what is believed to be the first ever human case of H10N3 bird flu, an uncommon and low pathogenic strain.

The incubation period is generally between 2-5 days, but an upper limit of 8 days is possible. Most patients have headache, malaise, high fever, sore throat, cough, shortness of breath, and myalgia. Conjunctivitis, watery diarrhea, abdominal pain, vomiting, pleuritic pain, and bleeding from the nose have also been reported. Respiratory distress, tachypnea, and inspiratory crackles are present on physical examination. Lymphopenia and thrombocytopenia are commonly present. The frequency of milder illnesses, subclinical infections, and atypical presentations such as encephalopathy is not known. Pregnant individuals are at increased risk for severe illness from influenza.

Atypical presentations of avian influenza have been reported. Patients have developed nausea, vomiting, and diarrhea preceding acute respiratory failure. Progression to acute respiratory distress syndrome (ARDS) and respiratory failure is common. Complications have included bacterial sepsis, pulmonary hemorrhage, and multi-organ failure. The mortality rate of hospitalized patients has been high due to progressive respiratory failure.

Codes

ICD10CM:
J09.X2 – Influenza due to identified novel influenza A virus with other respiratory manifestations

SNOMEDCT:
442438000 – Influenza caused by Influenza A virus

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Differential Diagnosis & Pitfalls

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Last Reviewed:04/12/2017
Last Updated:08/09/2021
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Emergency: requires immediate attention
Avian influenza
A medical illustration showing key findings of Avian influenza : Abdominal pain, Cough, Fever, Headache, Rhinorrhea, Dyspnea, Myalgia, RR increased
Imaging Studies image of Avian influenza - imageId=3042057. Click to open in gallery.  caption: ' Hien, Liem, Dung, San, Mai, Chau, Suu, Dong, Mai, Thi, Khoa, <br> Phat,Truong, Long. "Avian Influenza A (H5N1) in 10 Patients in <br> Vietnam." New England Journal of Medicine 2004; 350:1179-1188. <br> http://content.nejm.org/cgi/content/full/350/12/1179 <br><br>'
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