Avian flu, or bird flu, refers to a group of diseases that result from infections with specific influenza viruses. These viruses infect birds and — rarely — spread among humans. One virus that causes bird flu is called H5N1.
So far, the virus has shown no signs of changing genetically to spread more efficiently among humans. However, due to the severity of the illness that the virus can cause, authorities continue to monitor for these genetic changes. H5N1 bird flu is fatal in 60% of cases.
The first outbreak of H5N1 avian flu in humans occurred in 1997 in Hong Kong. Overall, authorities have reported more than 700 instances of human H5N1 infection — in Africa, Asia, and Europe. Indonesia, Vietnam, and Egypt have had the highest numbers of cases.
Below, we investigate whether the H5N1 virus poses a global threat to health. We also describe the symptoms, causes, and treatments of H5N1 bird flu.
It is not easy for the H5N1 virus to transmit from animals to humans. It is even harder for the virus to pass from person to person.
However, if a person with seasonal flu then develops this bird flu, the H5N1 virus may be able to exchange genetic information with the seasonal flu virus. If this happens, the H5N1 virus could gain further ability to spread among people.
A strain of avian flu virus that develops greater ability to spread among humans could have serious consequences.
At present, controlling outbreaks of bird flu in animals and humans can help keep the virus from developing this capacity and prevent further spread that could lead to a pandemic.
Type A strains of the influenza virus, including H5N1, cause avian flu, or bird flu.
The H5N1 virus can infect several types of birds. Authorities have mostly reported the disease in farmed poultry, such as chickens, geese, turkeys, and ducks.
However, in January 2015, healthcare professionals found a wild duck in the United States that had H5N1 avian flu. Virologists — scientists who focus on viral diseases — have also found the virus in pigs, cats, dogs, and beech martens, as well as leopards and tigers in captivity.
The virus spreads easily among birds through their saliva, nasal secretions, feces, and feed. They can acquire the virus from contaminated surfaces, such as cages and other farming equipment.
Most people with the infection have had direct contact with infected poultry or objects that have touched contaminated bird feces or secretions, according to the CDC.
Until now, very few cases of human-to-human transmission have occurred.
The most recent reported incidence of H5N1 bird flu occurred in Malaysia in March 2017. The outbreak killed a number of chickens, but the authorities reported no human infections.
The “incubation period” of a virus is the amount of time between the infection and the host developing symptoms. The virus may be contagious during this time.
A 2019 review estimates the incubation period of H5N1 in humans to be at most 7 days, but more commonly 2–5 days.
H5N1 bird flu can cause severe symptoms in humans. A person may experience more serious typical flu symptoms, including:
- a fever of above 100.4ºF (38ºC)
- a cough
- muscle aches
The following signs and symptoms of the illness can range from mild to severe:
- a hoarse voice
- a sore throat
- an upset stomach, sometimes involving diarrhea
- abdominal pain
- chest pain
- an altered mental state
Some people with H5N1 bird flu develop severe respiratory problems, including pneumonia and breathlessness.
According to a World Health Organization (WHO) report from 2005, shortness of breath occurs around 5 days after the first symptoms appear.
The condition of a person with H5N1 avian flu can deteriorate rapidly. They may experience respiratory failure and multiple organ failure, leading to death.
Humans can acquire the infection and develop the illness after coming into unprotected contact with birds who are carrying the virus. Human-to-human transmission is rare.
According to the Food and Agriculture Organization of the U. S., the following activities may lead to the illness in humans:
- touching infected birds
- touching or breathing in feces or other secretions of infected birds
- preparing infected poultry for cooking
- slaughtering or butchering infected poultry
- handling birds for sale
- attending markets that sell live birds
The infection can transmit to humans through a person’s eyes, nose, or mouth. However, some people develop the infection even without exposure to birds with the virus.
Eating cooked poultry or eggs does not cause infection. However, it is important to cook poultry until its internal temperature is at least 165º F (74º C) and eggs until both the whites and yolks are firm.
Bird droppings may contain the virus and can contaminate feed, equipment, vehicles, shoes, clothing, soil, dust, and water. The bodies, and particularly the feet, of animals can also carry the H5N1 virus.
Receiving a diagnosis of H5N1 avian flu early can lead to a better outlook.
Before arriving at a diagnosis, the doctor will:
- consider the person’s symptoms
- look for signs of bird flu
- ask about recent travel
- ask about any contact with birds
- collect a respiratory specimen and send it to a lab for analysis
If a person gives this respiratory sample in the first few days of the illness, the results of the analysis are likely to be more accurate.
In 2009, the FDA approved the AVantage A/H5N1 flu test, which can detect the presence of the virus in nose or throat swabs.
The test can identify a specific protein, called NS1, which indicates the presence of the virus.
Because H5N1 avian flu is rare, a physician would not expect to make this diagnosis, unless the person has been in contact with birds or recently stayed in a place where H5N1 infection is likely.
Doctors should administer oseltamivir (Tamiflu) within 48 hours of symptoms developing. However, as mortality rates are high, doctors may also administer the medication after 48 hours to improve the individual’s outlook.
Tamiflu has a standard dosage of 75 milligrams for people aged 13 years or older. Children under this age will need a smaller dosage, as will people with kidney problems or end stage renal disease.
A standard course of Tamiflu is 5 days, though a doctor may recommend a longer course for a person who is severely ill or who has a weakened immune system.
People for whom H5N1 bird flu causes gastrointestinal problems may not be able to absorb the drug as effectively as people who do not experience abdominal pain, diarrhea, or vomiting.
Also, studiessuggest that some cases of H5N1 avian flu may be resistant to this treatment.
Anyone who has diagnosed or suspected avian flu should remain isolated, at home or in a hospital.
Apart from taking Tamiflu, healthcare professionals advise people to:
- drink plenty of fluids
- eat a balanced and healthful diet
- take other medications to help manage the pain and fever
Complications, such as bacterial pneumonia, are common in people with H5N1 avian flu. Anyone with bacterial pneumonia will need to take antibiotics, and some people may need supplemental oxygen.
It is not possible to prevent bird flu from spreading. However, authorities can help communities prepare for possible infections by monitoring bird migration patterns.
Vaccination is available for seasonal flu but not bird flu.
According to the WHO, vaccines for H5N1 infection have been developed but are not yet ready for widespread use.
Individuals can minimize the spread of bird flu by taking precautions. These include:
- Hand hygiene: Wash the hands regularly with warm water and soap before and after using the bathroom, handling food, or coughing.
- Coughing: It is best to cough into an elbow or tissue and carefully dispose of used tissues — also, touching a surface after coughing into the hands can leave the virus on the surface, allowing it to spread.
- Isolation: Those who have symptoms should stay away from public places and avoid contact with people, whenever possible.
The WHO explain that the seasonal flu vaccine does not protect people from H5N1 avian flu.
Precautions around birds
When preparing meals, do not use the same utensils for cooked and raw meats. Before and after handling raw poultry, it is essential to wash the hands with soap and water.
Avoid dead or sick birds. To remove dead birds, call the relevant local authority. People who work with domestic birds should follow local and national guidelines.
Anyone traveling to an area in which avian flu may be active should avoid:
- bird feces
- live animal markets
- poultry farms
Being aware of the risks of infections — and taking all necessary precautions — is an effective way to avoid these illnesses.
People in areas with confirmed outbreaks of H5N1 avian flu should take every precaution and seek urgent medical advice if they start to notice symptoms, especially if they handle poultry or birds on a regular basis.
H5N1 bird flu can cause severe symptoms, and it has a high mortality rate. However, the virus does not transmit easily among humans, and the risk of a pandemic is low.
There is no vaccine available, but maintaining hand hygiene, isolating, and coughing only into an elbow or tissue can reduce the chances of acquiring or transmitting the virus.