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.
The H5N1 virus can cause severe flu with a high mortality rate.
However, according to the Centers for Disease Control and Prevention (CDC), transmission among humans is rare.
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
- malaise
- fatigue
- an upset stomach, sometimes involving diarrhea
- nausea
- vomiting
- abdominal pain
- chest pain
- an altered mental state
- seizures
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.
Source: Medical News Today
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