Influenza – Everything you need to know! – Thora Paul

What is Influenza virus?

Influenza virus (derived from the Latin word for ‘influence’) commonly known as the ‘flu’ is an enveloped single-stranded RNA virus which belongs to the Orthomyxoviridae family. There are 4 main types of influenza virus, Influenza A, B, C and D. Influenza virus A & B cause the most severe human illnesses and symptoms. Influenza A can be divided into subtypes, clades and sub-clades. Influenza B can be divided into lineages, clades and sub-clades.

The structure of Influenza virus 

Influenza virus is composed of an eight segmented genome. Before the production of proteins needed to allow infection of the host’s cells the negative-sense RNA must be converted into positive-sense RNA. The Influenza virus has haemagglutinin and neuraminidase glycoproteins on the outside membrane. Haemagglutinin glycoprotein allow viral recognition by binding to receptors which enables entry into the host’s cell. Neuraminidase glycoproteins however, allow the release of virion copies (virus particles) to complete the infectious cycle.

Figure 1: Internal and external structure of influenza virus.

How influenza spreads

The influenza virus, which is highly contagious, attacks an individual’s respiratory system. The virus spreads via droplets when an infected individual talks, coughs or sneezes. The virus can gain entry into the body of a nearby person via the mouth, nose or eyes. The virus may also gain entry when individuals touch surfaces with the virus and then touch their mouth, nose or eyes so effective hand washing more is very important.

Viral replication occurs in the nucleus of the host cell.

Figure 3: The viral replication cycle.


Symptoms can range from mild to severe, some symptoms include, but are not limited to: sore throat, cough, fever, fatigue and rhinorrhoea (runny nose). Some individuals may suffer from diarrhoea and vomiting. Influenza virus mutates rapidly which causes antigenic drift and thus different strains of the virus are produced, the best way to protect yourself is by getting an Influenza vaccine each year.

My thoughts

The 1918 ‘Spanish Flu’ pandemic occurred due to a highly virulent strain of Influenza virus, resulting in approximately 50 million deaths worldwide. Today Influenza virus is still very prevalent, and scientist continue to work on ways to best protect the public. I think it is important to be aware of how influenza virus spreads and ways in which we can protect ourselves and others.




CDC, (2019) Key Facts About Influenza (Flu) [accessed 13/10/21]


CDC (2021) Key Facts About Influenza (Flu). [online] Available at: [accessed on 10/11/21]


Clancy, S. (2008) Genetics of the influenza virus. Nature Education 1(1):83 [Online] Available at: [Accessed on 13th November 2021]


Dou, D., Revol, R., Östbye, H., Wang, H., & Daniels, R. (2018). Influenza A Virus Cell Entry, Replication, Virion Assembly and Movement. Frontiers in immunology9, 1581.


Kosik, I., & Yewdell, J. W. (2019). Influenza Hemagglutinin and Neuraminidase: Yin⁻Yang Proteins Coevolving to Thwart Immunity. Viruses11(4), 346.


Krammer, F., Smith, G., Fouchier, R., Peiris, M., Kedzierska, K., Doherty, P. C., Palese, P., Shaw, M. L., Treanor, J., Webster, R. G., & García-Sastre, A. (2018). Influenza. Nature reviews. Disease primers4(1), 3.


Kumar, B., Asha, K., Khanna, M., Ronsard, L., Meseko, C. A., & Sanicas, M. (2018). The emerging influenza virus threat: status and new prospects for its therapy and control. Archives of virology163(4), 831–844.


Mayo clinic (2021) Influenza (Flu) [accessed 16/10/21]


van Aken J. (2007). Ethics of reconstructing Spanish flu: is it wise to resurrect a deadly virus?. Heredity98(1), 1–2.