Introduction
Influenza A is a highly contagious respiratory disease caused by the type A influenza virus, a helically-shaped single-stranded RNA virus. (Jung & Lee, 2020). According to the Australian National Notification Data ( NNDS), there was a total of 225,332 reported cases of influenza virus infection between the beginning of the year to 9th October 2022. Among this number, 308 of the patients died due to the disease. Notably, 99% of the deaths occurred due to infection from the Influenza type A virus (Australian Government, 2022). The notification rates of infection were also highest among people aged between 5 to 9 years at 1,847.0 notifications per 100,000 people. The second highest group was people under five, with 1,532.7 children per 100,000 suffering from the disease. The third highest group of people infected by the Influenza virus were people aged between 10 to 19 years old, at 1,272.2 infections per 100,000 people (Australian Government, 2022).
Numerous risk factors are associated with the Influenza virus. Examples of these risk factors are, Firstly, a person’s age; younger people tend to have a higher infection rate, while older patients who acquire the disease have a higher risk of developing a complication or succumbing to the disease. Secondly, immunocompromised individuals, pregnant women, and people with underlying respiratory and medical conditions are also more likely to get infected. Lastly, medical personnel who work with infected people or professionals who work with children have an increased risk of contracting the disease (Demicheli et al., 2018).
Pathophysiology of Influenza A
After an individual is exposed to the Influenza virus, it enters the host’s body and begins replication in the respiratory system’s epithelium cells before invading the neighbouring immune and non-immune cells. This replication is facilitated by two major proteins found on the surface of the Influenza A virus; the neuraminidase NA and the hemagglutinin (HA) (Jung & Lee, 2020). The replication process begins when the virus’s hemagglutinin binds to the silica acid on the host cell’s glycolipid receptors. After binding, the virus fuses with the cell’s endosomal membrane and releases its nucleocapsid into the host cell’s cytoplasm (Kalil & Thomas, 2019). The viral nucleocapsid enters the host’s nucleus and undergoes transcription. On the other hand, the virus’s neuraminidase and hemagglutinin begin polymerisation, acylation, and glycosylation (Jung & Lee, 2020). They also travel to the host cell’s plasma membrane to undergo a budding process. After completing the transcription and budding process, the sialic receptors on the host membrane are destroyed by the virus’s neuraminidase, leading to the replicated viral cells being released outside the host’s cell, where they continue infecting new healthy cells.
Notably, once the virus enters the host’s body, the first line of defence against infection is the host’s innate immunity. This immunity leads to the development of pro-inflammatory responses as a way for the body to fight off infection. (Demicheli et al., 2018). The body’s innate immune mechanism becomes triggered when pattern recognition receptors (PRRs) recognise the virus. Different PRRs carry out this recognition function; examples are retinoic-acid-inducible genes and Toll-like receptors. The recognition of the virus by these PRRs results in the secretion of type 1 IFNs and pro-inflammatory cytokines leading to the establishment of an anti-viral immune microenvironment. Natural Killer cells are additionally activated during the innate immune response to release granzyme and perforin, which help lyse any infected cells (Kalil & Thomas, 2019). Macrophages, neutrophils, and monocytes further prevent the virus’s spread by phagocytosing apoptotic cells that are infected.
However, when the innate response is not able to fight off the viral infection, the body uses its adaptive immunity. Dendritic cells act as a link between innate and adaptive immunity. During adaptive immunity, antibodies specific to the Influenza virus’s NA and HA are used by the body to prevent viral entry into the body. Nonetheless, the Influenza A virus may evade the adaptive immune response by altering its antigen through antigenic drifts leading to the creation of NA and HA proteins that the pre-existing antibodies cannot recognise. Moreover, the viral re-assortment of the virus’s genome leads to the generation of new strains of the Influenza A virus, which the body does not recognise and is hence more susceptible to (Jung & Lee, 2020).
The Influenza A virus affects the body’s homeostatic response by causing pulmonary inflammation. This is because the rapid replication of the virus damages the host’s pulmonary tissues and cells. This results in the accumulation of dead cells in the host’s respiratory system. These dead cells lead to the development of respiratory distress, which is characterised by fever, congestion, and myalgia. Infection in the lower respiratory tract also results in the creation of pneumonia which progresses to form acute respiratory distress syndrome. In extreme cases, lung inflammation may lead to multi-organ failure if severe respiratory distress is not treated (Verweij et al., 2020).
Pharmacological Treatments
The primary type of treatment that is used against Influenza is Neuraminidase Inhibitors such as zanamivir and oseltamivir. They affect the disease’s pharmacology by blocking its activity by binding to the active site of the virus’s neuraminidase. This results in the viral particle failing to leave the infected cells, preventing the virus from infecting more cells. Neuraminidase Inhibitors are hence required to be administered 48 hours after one is exposed to the virus so as to control its replication process. Another type of drug that inhibits Influenza A’s viral replication is Amatidine. The drug inhibits viral replication by blocking the function of the virus’s M2 protein (Verweij et al., 2020). However, Amatidine is not commonly used due to its high level of resistance. Nonetheless, NA inhibitors such as zanamivir and oseltamivir are preferred due to their low toxicity and reduced chances of resistance (Topoulos et al., 2019).
Additionally, influenza vaccines are administered to help the body gain immunity against the disease. The vaccine acts by creating antibodies or memory cells specific to the influenza virus. There are two primary vaccine types: inactivated and live attenuated Influenza. The vaccine’s mode of action varies since the influenza virus has two types of antigens; neuraminidase (NA) and hemagglutinin (HA). The NA antibodies work by aggregating the viruses on the cell’s surface, thereby reducing the among of viruses that can be released from an infected cell, while HA antibodies target the head of the HA protein of the virus, thereby preventing it from invading the host’s body (Demicheli et al., 2018).
Key Patient Education Considerations
The key patient education considerations are :
- Individuals should eat a healthy diet, exercise, and get plenty of rest. A healthy diet that contains fruit and vegetables which are rich in antioxidants that help the body’s immunity fight against the influenza virus (Maldonado et al., 2019).
- Patients should be taught the importance of hygiene by washing hands often with soap and water and carrying an alcohol-based sanitiser. This helps reduce the chances of the disease being spread by hand.
- Medical personnel should educate patients on the importance of avoiding regularly touching their nose, mouth, and eyes to reduce the spread of the virus through the mucous membrane or the conjunctiva.
- Limiting close interaction with people suspected to be suffering from the influenza virus and avoiding contact with people if one is infected with the disease.
- Encourage people to sneeze into their elbows and not their hands to help reduce the transmission of the disease in the community setting (Maldonado et al., 2019).
- Teach people the importance of regularly cleaning and disinfecting surfaces. This helps reduce the spread of the disease since influenza viruses can remain on the surface for up to 48 hours after deposition.
- Encourage people to get vaccinated against the disease. Vaccination against the disease helps people gain immunity against the infection.
- Inform people of the importance of taking anti-viral drugs. The drugs used to treat the disease help reduce the spread of the infection in the patient’s body through the inhibition of viral replication (Maldonado et al., 2019).
Conclusion
In summary, Influenza A is a type of respiratory disease that is contagious and is caused by a single-stranded RNA virus from the orthomyxovirus family. After a person becomes infected with the virus, it enters the body’s epithelial cells and begins replication. The Influenza A virus can be treated with the use of NA inhibitors, which prevent viral replication by binding to the active site of the virus’s neuraminidase. Lastly, some examples of patient education considerations to help reduce infection are encouraging people to maintain a healthy diet and hygiene, limiting interaction with sick people, and getting vaccinated annually.
References
Australian Government. (2022). AUSTRALIAN INFLUENZA SURVEILLANCE REPORT. No. 14. https://www1.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-ozflu-flucurr.htm/$File/flu-14-2022.pdf
Demicheli, V., Jefferson, T., Ferroni, E., Rivetti, A., & Di Pietrantonj, C. (2018). Vaccines for preventing Influenza in healthy adults. Cochrane database of systematic reviews, (2). https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD001269.pub6/full
Jung, H. E., & Lee, H. K. (2020). Host protective immune responses against Influenza A virus infection. Viruses, 12(5), 504. file:///C:/Users/user/OneDrive/Documents/viruses-12-00504%20(3).pdf
Kalil, A. C., & Thomas, P. G. (2019). Influenza virus-related critical illness: pathophysiology and epidemiology. Critical care, 23(1), 1-7. https://link.springer.com/article/10.1186/s13054-019-2539-
Maldonado, Y. A., Zaoutis, T. E., Banerjee, R., Barnett, E. D., Campbell, J. D., Caserta, M. T., … & COMMITTEE ON INFECTIOUS DISEASES. (2019). Recommendations for prevention and control of influenza in children, 2019–2020. Pediatrics, 144(4). https://publications.aap.org/pediatrics/article-abstract/144/4/e20192478/38469
Topoulos, S., Giesa, C., Gatermann, S., Fussen, R., Lemmen, S., & Ewig, S. (2019). Analysis of acute respiratory infections due to influenza virus A, B, and RSV during an influenza epidemic 2018. Infection, 47(3), 425-433. https://link.springer.com/article/10.1007/s15010-018-1262-x
Verweij, P. E., Rijnders, B. J., Brüggemann, R. J., Azoulay, E., Bassetti, M., Blot, S., … & van de Veerdonk, F. L. (2020). Review of influenza-associated pulmonary aspergillosis in ICU patients and proposal for a case definition: an expert opinion. Intensive care medicine, 46(8), 1524-1535. https://link.springer.com/article/10.1007/s00134-020-06091-6
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