Bird flu is caused by avian influenza A viruses, which usually spread among birds, not people. One subtype, H5, is spreading worldwide in wild birds, causing sporadic outbreaks in U.S. poultry and dairy cows, and reaching a growing number of mammals. It has caused some rare human infections. CDC rates the current public health risk from H5 bird flu as low, and it is monitoring the situation closely, working with states to follow people exposed to animals that are or may be infected.
Image from CDC's page on bird flu.
How people catch it
Wild water birds are the natural hosts of these viruses. Infected birds and other animals shed virus in their mucus, saliva and feces. People rarely get bird flu; when they do, it is usually through direct contact with infected animals without recommended protective equipment (PPE).
| Route | Examples |
|---|---|
| Infected animals | Direct contact with sick or dead birds or other infected animals — the main risk |
| Contaminated surfaces | Surfaces, litter or bedding soiled with animal secretions or droppings |
| Food | Raw or undercooked poultry or eggs, or unpasteurized milk from infected cows |
| Air | Droplets or dust carrying the virus |
Properly cooked or pasteurized products are safe. No person-to-person spread has been identified in the United States. Very limited spread between people has been reported in other countries in the past, meaning the virus passed to one or two people and went no further.
Subtypes known to have infected people include H5, H6, H7, H9 and H10.
Symptoms
Illness in people has ranged from no symptoms to severe disease and death, but most U.S. H5 cases so far have been mild.
Mild symptoms can include:
- eye redness and irritation (conjunctivitis) — the main symptom in recent U.S. H5 cases;
- mild fever (100°F / 37.8°C or higher) or feeling feverish — though fever is not always present;
- cough, sore throat, runny or stuffy nose;
- muscle or body aches, headaches, fatigue;
- less often, diarrhea, nausea or vomiting.
Moderate to severe illness can bring high fever, shortness of breath or difficulty breathing, altered consciousness and seizures.
Who is at higher risk
People with close or prolonged contact with infected birds or animals, or contaminated places — through work or recreation — are most likely to be infected. Older age, delayed medical care and underlying medical conditions can make illness worse.
Prevention
- Keep your distance. Avoid direct contact with sick or dead wild birds, poultry and other animals; watch them from afar. If you must handle them, including dairy cows, wear recommended PPE.
- Avoid contaminated material, such as litter or bedding soiled by animals with confirmed or suspected infection.
- Skip raw milk. Don't touch or drink raw milk or raw-milk products, especially from animals that may be infected. Pasteurization kills viruses such as avian influenza in milk.
- Cook thoroughly. Cook poultry, eggs and beef to a safe internal temperature (CDC's safe temperature table).
Testing and treatment
Samples from people with suspected bird flu are tested first by a state public health laboratory; positives there are "presumptive positive" and go to CDC for confirmation.
Flu antiviral drugs treat bird flu. Anyone who develops symptoms after exposure to infected animals should get an antiviral (oseltamivir) as soon as possible — ideally within 48 hours of symptoms starting, without waiting for test results. People exposed without proper PPE, or whose PPE failed, may be offered antivirals even without symptoms.
Vaccines
No bird flu vaccine is recommended for the public or sold commercially, and seasonal flu vaccines are not designed to protect against it. CDC has developed H5 candidate vaccine viruses — the starting material for flu vaccines — that match, or nearly match, the hemagglutinin protein of recent clade 2.3.4.4b H5N1 viruses from people, birds and other mammals. Early analysis suggests a vaccine made from them would protect well against the H5N1 viruses now circulating in animals.
Why it matters
Avian influenza viruses are very different from seasonal human flu. Because people have little existing immunity, one that learned to infect people easily and spread efficiently between them could cause a pandemic. None, H5N1 included, has done so yet — but the chance of severe human infections is why prevention and surveillance continue.
In animals
H5 bird flu is widespread in wild birds worldwide and turning up in more and more animals, besides outbreaks in poultry and U.S. dairy herds.
- Waterbirds such as ducks, geese and swans, and shorebirds such as storks, can carry the virus, usually without getting sick.
- Poultry such as chickens and turkeys can become very sick and die.
- Backyard birds — cardinals, robins, sparrows, blue jays, crows, pigeons — mostly do not get infected.
- Mammals, including dairy cows, can be infected, with illness ranging from mild to fatal.
What CDC is doing
Using a One Health approach, CDC works with the U.S. Department of Agriculture, the Food and Drug Administration, the Administration for Strategic Preparedness and Response, and state public health and animal health officials. Its work focuses on:
- surveillance and diagnostics;
- monitoring exposed people, and guidance for the public, health departments and clinicians;
- virology, and tracking genetic changes in the virus.
Sources
Based on "About Bird Flu," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
1
0
0
0
Comments
