Introduction
Avian flu is also referred to as bird flu which is caused by a type of influenza virus, avian type A influenza virus. These viruses generally infect aquatic birds and can infect other birds, domestic poultry, animal species, and rarely humans. It can also be transferred from person to person, and there is a need for hospitalization and an intensive care unit (ICU). The infection can be commonly seen in wild aquatic birds such as swans, ducks, storks, plovers, and sandpipers.
What Are the Causes of Avian Flu?
Avian flu or bird flu is caused by the avian type A influenza virus. Avian viruses can cause infection in humans by adapting to the host with the influenza virus or by antigenic drift. The strains of the high pathogenic avian influenza virus mostly get activated in the host organs, whereas low pathogenic avian influenza virus is activated in the particular organs with protein modifying enzymes. This differentiates the signs and symptoms of the infection caused by both the pathogenic avian viruses.
What Are the Symptoms of Avian Flu?
-
The onset of symptoms starts after two to four days of exposure to the avian virus but also over a week after transmission.
-
The symptoms can be observed only in patients who are in need of hospitalization.
-
In most patients, the symptoms of this disease are similar to the flu-like viral infection.
-
In patients due to avian influenza outbreak, a thorough evaluation of the history is mandatory to rule out that the cause is due to avian influenza.
-
Higher suspicious activity is noted in patients who are high with bird contact and severe viral symptoms associated with encephalopathy or organ failure.
-
People who work in culinary industries or poultry usually have frequent contact with birds and are more prone to contact with the active virus.
-
A majority of patients hospitalized due to avian flu are mostly related to poultry.
-
An environment to human and human-to-human transmission is highly possible with the avian influenza virus and is confirmed in the cases of H7N9 infection.
-
Different characteristics of the infection are manifested by different strains of the avian influenza virus.
-
Strains of H5N1 manifest with fever, lower respiratory tract symptoms, and rarely with non-bloody, non-inflammatory diarrhea.
-
Strains of H7N9 and low pathogenic avian influenza virus cause conjunctivitis.
-
Certain symptoms of avian flu symptoms include-
-
Common flu.
-
Fever.
-
Headache.
-
Muscle aches.
-
Shortness of breath.
What Are the Subtypes of the Influenza Virus Affecting Humans?
Humans can be infected by avian influenza subtypes such as A(H5N1), A(H9N2), and A(H7N9). Avian influenza A viruses are broadly grouped into two categories such as HPAI (high pathogenic avian influenza) A viruses and LPAI (low pathogenic avian influenza) A viruses.
-
Low Pathogenic Avian Influenza (LPAI) A Viruses: Most of the low-pathogenic avian influenza A viruses are less pathogenic and may or may not present with signs and symptoms. They usually show mild signs of infection in poultry or chickens and wild birds. Some of the low pathogenic avian influenza viruses undergo mutation and may transform into high pathogenic avian influenza viruses.
-
High Pathogenic Avian Influenza (HPAI) Viruses: High pathogenic avian influenza virus generally causes severe infection associated with high mortality in infected poultry. A few avian viruses, such as A (H5) and A (H7), are highly pathogenic, whereas most of the avian viruses A (H5) and A (H7) belong to a low pathogenic group.
How Does the Avian Influenza Virus Affect Poultry?
Domesticated birds, such as chicks, ducks, and turkeys, are also infected with avian influenza type A viruses through infected poultry or with surface contact with the contaminated viruses.
What Are the Types of Influenza Viruses?
There are three types of influenza virus generally, and they are classified into Type A, Type B, and Type C.
How To Diagnose Avian Flu?
-
A proper history evaluation presenting with flu-like viral symptoms and recent poultry culling or bird handling helps in the easy diagnosis of the disease.
-
Another testing should be done on organ dysfunction and respiratory impairment, which occurs as a sequela of avian influenza virus infection.
-
Rapid antigen testing for the avian influenza virus is recommended but is often shown up with a false negative in the confirmed cases.
-
A nasopharyngeal swab or aspirate is mostly preferred for laboratory testing.
-
Other body fluids are considered for testing as an alternative to nasopharyngeal swabs.
-
RT-PCR identification is the most standard method for diagnosis of the avian influenza virus, in which the avian virus can be easily identified within a few days of the onset of the disease.
How To Manage Avian Flu?
-
Avian flu can be effectively managed with antiviral medications and supportive care.
-
The treatment is aimed at controlling the sequelae of the infection.
-
In the case of volume loss or electrolyte imbalance, patients are recommended to receive volume resuscitation and methods to correct fluid imbalances.
-
In patients presenting with high fever, antipyretic medications are prescribed.
-
Patients with respiratory complications are managed with supplemental oxygen and monitored for signs of deterioration, as these patients are at high-risk and in need of intubation and mechanical ventilation.
-
In severe manifestations, the infection can result in multiorgan failure and dysfunction, which can be closely monitored and provided with the appropriate treatments.
-
In the treatment of patients infected with H5N1, the prescription of neuraminidase inhibitors, particularly, Oseltamivir, is recommended.
-
Oseltamivir, with a dosage of 75 milligrams daily as prophylaxis for seven to ten days, is recommended for high-risk groups.
-
Low and moderate-risk groups are not strongly recommended for chemoprophylaxis.
Conclusion
Influenza virus strains primarily infect birds but can also infect humans. Contact with sick birds is the most common way to contract this type of flu. It can also be passed from one person to the next. Avian flu is highly considered to be a deadly disease since it involves multiorgan dysfunction and organ failure and presents with a high mortality rate. The avian virus is much more dangerous in affected humans, and the prognosis in hospitalized patients is generally poor. The severe complication of his disease is organ failure, iatrogenic injury during treatment, or coinfection.
