What Is Avian Influenza A (H5N1) Virus? How to Use Avian Influenza (Bird Flu) Rapid Test Kit?
The recent decades have seen unprecedented outbreaks of highly pathogenic avian influenza A subtypes among poultry and human populations. These outbreaks have led to significant concerns regarding whether the world may be about to face a bird flu pandemic in the near future. After identifying several key events that mark the progression of the avian influenza subtype H5N1 towards becoming a pandemic, the Senior United Nations System Coordinator for Avian and Human Influenza has warned the world against an outbreak that could kill anywhere between 5 million to 150 million people in 2005. So, can bird flu be a pandemic in waiting? Read along to learn more about Avian Influenza A, its transmission routes, global spread, and symptoms, along with its detection with the Avian Influenza (Bird Flu) Rapid Test Kit.
What Is Avian Influenza A (H5N1) Virus?
Avian influenza is a type A influenza virus of the genus Alphainfluenzavirus of the family Orthomyxoviridae. It is a single-stranded RNA virus with a genome consisting of eight negative-sense RNA segments. Given the potential combinations between the main virion antigens haemagglutinin (HA) and neuraminidase (NA), the influenza A virus theoretically has thousands of antigenic subtypes. So far, 16 HA subtypes and 9 NA subtypes have been identified, with two additional HA and NA subtypes detected in bats.
H5N1 is a subtype of influenza A that is one of the major causes of avian influenza in humans, birds, and other species. Avian influenza viruses are categorized into two main types based on their virulence. Highly pathogenic avian influenza (HPAI) refers to viruses that can cause systemic lethal infection with high mortality. On the other hand, low-pathogenic avian influenza (LPAI) denotes viruses that cause localized infections with much lower mortality. Haemagglutinin (HA), which binds the virus to the cell that is being infected, has been detected as the primary facilitator of this variation in pathogenicity. Together with neuraminidase (NA), which is responsible for releasing progeny viruses from infected cells, hemagglutinin (HA) also specifies the structure of proteins most relevant for medical and diagnostic purposes.
Highly pathogenic avian influenza virus H5N1 [HPAI A(H5N1)], which is a bird-adapted strain of H5N1, is commonly known as the causative agent of avian influenza or bird flu in humans. Following its initial discovery in 1959 in Scotland, the strain further mutated towards higher pathogenicity between 1999 and 2002 to create the dominant strain of HPAI A(H5N1) in 2004. As opposed to the low-pathogenic avian influenza H5N1 (LPAI H5N1), which is not known to cause any disease in humans, highly pathogenic avian influenza H5N1 has been regarded as one of the world’s most significant pandemic threat due to its high virulence, high lethality, endemic presence, ongoing mutations, and expanding host reservoir. Thus, despite the inefficiency of its animal-to-human and human-to-human transmission, avian influenza has been highly monitored by global and local health authorities worldwide.
How Does the Avian Influenza A (H5N1) Virus Transmit?
According to the Centers for Disease Control and Prevention (CDC), most cases of avian influenza infections in humans have been linked to unprotected contact with infected birds or contaminated surfaces. The virus can be contracted and transmitted by both domestic birds and wild birds. There is very limited evidence of its human-to-human transmission. While animal-to-human transmission of avian influenza is rare, people can get infected if a sufficient amount of the virus enters the body through the eyes, nose, or mouth. Transmission may involve the inhalation of droplets and aerosols or direct contact with infected animals and contaminated surfaces. The majority of avian flu infections in humans have been reported following close, prolonged, and unprotected contact with infected birds or contaminated surfaces. Although there is some evidence that the virus can transmit through uncooked or undercooked poultry meat consumption, no human avian flu has so far been linked to properly handling or consuming properly cooked poultry meat and products.
How Common Is Avian Influenza (Bird Flu)?
HPAI A(H5N1) is primarily considered an avian disease. Transmission of the virus from infected birds is relatively rare and inefficient. Moreover, there is little evidence supporting its human-to-human transmission. Thus, the overall circulation of HPAI A(H5N1) across human populations has so far been limited. According to the World Health Organization (WHO), HPAI A(H5N1) has caused 861 confirmed human cases of avian influenza, with 455 deaths between 2003 and 2020. Therefore, the strain is characterized by a case-fatality rate as high as 60% despite its limited circulation among humans. With the rapid occurrence of several vital events indicative of a potential progression of the virus to become a pandemic, there is growing concerned regarding the possible mutations that may enhance the capability of the strain to sustained human-to-human transmission.
What Are the Symptoms of Avian Influenza (Bird Flu)?
The symptoms associated with avian influenza are largely similar to seasonal influenza in humans. Infection may present with common influenza symptoms such as fever, cough, sore throat, runny/congested nose, headache, myalgia, fatigue, conjunctivitis, difficulty breathing, and diarrhea. Symptom severity may range from mild to severe. Relative to seasonal influenza, however, avian influenza has a much higher case fatality rate in humans due to the development of severe disease and complications.
How to Use the Avian Influenza (Bird Flu) Rapid Test Kit?
Rapid detection of avian influenza is of critical importance for timely intervention and transmission control. Designed to address this need, the Avian Influenza (Bird Flu) Rapid Test Kit is a rapid chromatographic immunoassay that detects influenza A-specific antigens in birds. Coming in a lateral flow assay format, the kit incorporates different sets of antibodies to target and capture antigens specific to influenza A that may be present in the collected samples. As the processed sample flows along the surface of the kit via capillary flow, these antibodies bind to and immobilize the viral antigens. In addition, the use of labeled antibodies enables the emergence of the control line (C), which indicates the validity of the results, and the test line (T), which indicates the positivity of the result. This technology has been utilized for the detection of various viruses, bacteria, and parasites of medical and veterinary concern.
All instructions concerning sample collection and procession are included in the manual within the test kit. These instructions should be followed carefully to ensure the validity and accuracy of the test results. Following the collection of the specified sample, the obtained sample is rotated and squeezed thoroughly within the extraction tube to ensure its transfer to the extraction buffer. Then, the dropper head is attached to the tube, the test cassette is placed on a flat surface, and the processed sample is added to the assigned well on the test cassette. The results should be read within the period specified in the manual.
REFERENCES
Bahadır, E. B., & Sezgintürk, M. K. (2016). Lateral flow assays: Principles, designs and labels. TrAC Trends in Analytical Chemistry, 82, 286–306. https://doi.org/10.1016/j.trac.2016.06.006
Chatziprodromidou, I. P., Arvanitidou, M., Guitian, J., Apostolou, T., Vantarakis, G., & Vantarakis, A. (2018). Global avian influenza outbreaks 2010–2016: a systematic review of their distribution, avian species, and virus subtype. Systematic Reviews, 7(1). https://doi.org/10.1186/s13643-018-0691-z
Horimoto, T., & Kawaoka, Y. (2005). Influenza: lessons from past pandemics, warnings from current incidents. Nature Reviews Microbiology, 3(8), 591–600. https://doi.org/10.1038/nrmicro1208
