Everything you need to know about bird flu

After the appearance of a case of avian influenza A(H5) after 8 years, this disease is receiving much attention and concern from the community.

Learn about bird flu

In mid-October, the National Institute of Hygiene and Epidemiology reported a case of a 5-year-old child in Phu Tho testing positive for the A(H5) influenza virus. This is the latest human case of avian influenza in Vietnam since February 2014.

Although well controlled, this disease still causes much concern. In that context, Dr. Phan Van Manh, Emergency Department, Central Hospital for Tropical Diseases, said that people need to be aware of the risk of infection with the avian influenza virus.

The bird flu case appeared after a long time causing concern for the community. (Photo: WTHR).

What is bird flu?

Dr. Manh said that in theory, influenza viruses belong to the Orthomyxoviridae family, including 4 types: A, B, C (can cause disease in humans) and D (mainly affects livestock and does not cause disease in humans).

While influenza C viruses cause sporadic disease in humans and pigs , influenza A and B viruses appear seasonally in humans worldwide . Annual seasonal influenza epidemics are estimated to cause 3–5 million cases of severe illness and 290,000–650,000 deaths.

"Humans can also be infected with influenza A viruses from animals (zoonotic influenza) such as avian influenza A viruses divided into types: A (H5N1), A (H5N6), A (H7N9), A (H7N7) and A (H9N2) or swine influenza A viruses including A (H1N1), A (H1N2) and A (H3N2) , " the expert informed.

Among them, avian influenza is caused by influenza A strains, which usually only infect wild birds and domestic poultry. However, some of them can infect humans such as H5, H7 and H9.

According to Dr. Manh, most cases of bird flu in humans are caused by Asian strains H5N1 and H7N9 .

Avian influenza can cause high mortality in poultry and can be transmitted to humans. (Illustration: MPR).

Avian influenza infection is often asymptomatic in wild birds but can cause very high mortality in domestic poultry.

In humans, the mortality rate from infection with A (H5N1), A (H5N6), and A (H7N9) viruses is much higher than that of seasonal influenza A or B. In contrast, most cases of influenza A (H7N7) and A (H9N2) infection are usually milder.

In the past, the first cases of H5N1 infection in humans were discovered in Hong Kong (China) in 1997. At that time, many patients had severe respiratory symptoms and a high mortality rate.

Human cases of H5N1 infection re-emerged in 2003 and 2004, reported mainly in Asia and the Middle East. Since 2014, human cases of H5N6 infection have also been reported, all in the Western Pacific region, mostly in China.

In early 2013, a large-scale outbreak of H7N9 avian influenza in humans occurred in several southeastern provinces of China. At that time, one-third of the cases were unfortunately fatal, mainly among the elderly.

Dr. Manh added: "In addition, other strains of bird flu also occur but not frequently, such as H5N8, H7N3, H7N7, H7N4 and H9N2."

How does avian influenza virus survive in nature?

Avian influenza A viruses have been isolated from more than 100 different species of wild aquatic birds worldwide, including ducks, geese, swans, gulls, terns, storks, and sandpipers.

"These species can be infected with the virus in the intestines and respiratory tract, which is then excreted through saliva, nasal secretions and feces. Farmed poultry are infected with influenza virus through these natural sources ," Dr. Manh analyzed.

In addition, avian influenza viruses are classified into two types: low pathogenic (LPAI) and highly pathogenic (HPAI) .

The expert said that low-virulence avian influenza viruses cause no symptoms or only mild symptoms in poultry such as ruffled feathers and reduced egg production. Meanwhile, highly virulent avian influenza viruses cause severe illness and high mortality rates in infected poultry.

"Chickens infected with HPAI A(H5) or A(H7) virus can affect multiple internal organs with mortality rates of up to 90-100%, usually within 48 hours," he added.

How does bird flu spread to humans?

According to the expert, most cases of human infection with avian influenza are transmitted from animals (typically poultry) after inhaling or coming into direct contact with secretions (saliva, mucus or feces) of infected animals.

The rate of direct human-to-human transmission of avian influenza viruses is very limited. However, influenza viruses have the ability to mutate rapidly. Therefore, they can completely lead to the ability to transmit from person to person, causing a pandemic.

How to recognize people with bird flu

"The symptoms of avian flu are quite similar to seasonal flu. However, the severity and mortality rate tend to be higher, although it depends on the virus strain ," Dr. Manh said.

According to him, people infected with bird flu may have no symptoms or mild symptoms such as fever, cough, runny nose, stuffy nose, sore throat, muscle aches, headache, and conjunctivitis.

Patients with bird flu often have symptoms quite similar to seasonal flu. (Illustration: towfiqu_barbhuiya).

Less common signs include diarrhea, nausea, vomiting, or seizures. Severe symptoms may include difficulty breathing or pneumonia, progressing to respiratory failure with a high mortality rate.

What to do when you have bird flu?

When there are clinical symptoms, along with a history of contact with people with avian influenza or poultry in an epidemic area, the patient should suspect being infected with avian influenza virus and immediately go to a medical facility capable of testing for influenza diagnosis, thereby being examined and diagnosed promptly.

Dr. Manh said that Oseltamivir (Tamiflu) is a specific drug to treat bird flu and should be used as soon as possible in unfortunate cases.

On the other hand, the World Health Organization (WHO) recommends against the use of corticosteroids, passive immunotherapy, or macrolide antibiotics in cases of influenza.

"Using antibiotics when the patient does not have a bacterial infection is also unnecessary and increases antibiotic resistance ," Dr. Manh added.

Therefore, patients should not buy medicine on their own when they have symptoms of flu. Instead, patients should go to a medical facility for proper diagnosis and treatment.

In addition, Dr. Manh recommends basic complementary treatments in treating flu that people can do at home: rest, provide adequate water and nutrition, reduce fever with paracetamol when fever is above 38.5 degrees Celsius, and balance fluid and electrolytes with oral rehydration solution.

How to prevent bird flu

According to Dr. Manh, vaccination campaigns for poultry against H5 and H7 influenza viruses can help actively prevent the spread of influenza viruses from wild birds to poultry.

"When we determine that the flu virus is present in poultry, we need to destroy the infected poultry to prevent the spread ," the expert affirmed.

On the other hand, people should avoid unprotected contact with wild birds (even those that appear healthy) and poultry that appear sick or dead.

Most importantly, avoid touching surfaces that may be contaminated with poultry saliva, mucus, or droppings.

When having to come into contact with poultry showing signs of illness, people need to use protective clothing such as gloves, medical masks, eye protection, and wash hands with soap and water after contact.

Health care workers who come into contact with patients also need to use protective clothing. For interventional or aerosol-generating procedures, N95 masks are required.

When suspected of being infected with the virus, the patient needs to isolate, avoid contact with relatives, wear a medical mask and go to the hospital for timely diagnosis.