Question 18. (2nd post) Which virus do you consider most important?

Q18. Which virus do you consider most important?

By Anna Shirley

In regards to this question, I chose influenza virus – this seems like an odd choice because its not something too many people worry about because it is both preventable and treatable. However, it has been documented throughout history and in 1918 it infected more than 2 billion people worldwide and killed 40 million – there has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. In addition, it has the ability to continually mutate and reinfect people with different strains – our complacency about this seemingly harmless virus has probably contributed to its spread. However, another outbreak could be just around the corner, which was briefly seen with the avian influenza outbreak in 2006; and in today’s modern society where there is a high level of global traffic and transport, it could soon become a pandemic. Not only are there porcine influenza, avian influenza and human influenza to worry about, but an avian influenza could combine with a human influenza to create a new influenza virus. Therefore, for all these reasons, influenza is of great importance and also concern.


Essay
The influenza virus has continued to plague humanity for centuries – from ancient Greece to modern day, influenza has been documented throughout history and has killed people in their millions. In ancient times it may have been difficult to treat those affected, but in today’s society we have access to a vast array of information and vaccines to target influenza - yet people still become infected by it and can even die because of it. In 1918 the influenza pandemic was at a magnitude never seen before. It started in the USA but soon spread to Europe during World War I, affecting France, England, Spain, Germany, and Russia, before continuing onto other parts of the world such as India, China, Japan, Africa, South America and even Alaska. It then eventually returned to the USA to cause complete devastation to the population. By the end of its reign it had infected more than 2 billion individuals and killed up to 40 million people. There has never been a greater loss of life in a comparable period in the history of the world, nor has there been since. Then by 1919, it seemed to disappear as enigmatically as it had appeared.

So why is influenza still a problem? In comparison to HIV, there are vaccines against the flu so it shouldn’t be as much of a problem - yet the total mortality of the 1918–1919 pandemic killed as many as 25 million in the first 25 weeks, but HIV/AIDS only killed 25 million in its first 25 years. In contrast to the common cold (another recurring viral disease) which has hundreds of different viruses, influenza only has 3 serotypes of influenza virus (A, B and C – of which A causes most illnesses), so it should be easier to contain. Yet, we have still not been able to control or eradicate this persistant virus that is both preventable and treatable. Why is it so hard to get this one virus under control?

The influenza virus is a single stranded RNA virus that consists of 2 main proteins, haemagglutinin and neuraminidase, which are arguably the most important determinants of virulence in the influenza virus.

These proteins are usually important for attaching to host cells and also detaching once they have replicated, but these proteins are also capable of continually changing through mutation (random point mutations during RNA translation), which produces new strains of the virus. This technique is called antigenic drift, and it is the ability of the virus to exploit this process that allows influenza to constantly adapt to avoid the immune system and no longer be recognised – the host has to now mount a new response to get rid of the new strain of influenza virus. Therefore, every winter we see a different strain of influenza which brings about a different vaccine every season – no one vaccine can eradicate influenza.

However, the influenza virus is also capable of antigenic shift – the exchange of genetic information. This occurs when there is co-infection of 2 different strains of influenza virus which exchange their RNA, creating a mixture of RNA which is packaged into new virions and creates new viruses with different antigens. The virus can even potentially infect other host species. More alarmingly, if a person is co-infected with both avian and human forms of influenza, antigenic shift can allow the formation of a new influenza virus, of which the human population has no immunity against, causing a pandemic.

Influenza is also of great concern because it is easily transmissible. It is spread from person to person by talking, coughing and sneezing via airborne droplets that enter the respiratory tract, allowing the virus to penetrate the host cell and replicate. In addition, the virus tends to emerge during winter when people are more likely to be indoors and in confined spaces – both of which facilitate the spread of the virus between people. For these reasons, the virus is easily capable of spreading and potentially exploding into a pandemic.

The economic cost of influenza is also of concern. In the US alone, it is estimated that influenza is responsible for costing the economy $10 billion dollars annually, and a potential threat of an influenza pandemic in the future could cost the world close to hundreds of billions of dollars in both direct and indirect costs – and in today’s volatile economic climate, we have to ask ourselves whether we could even afford an influenza pandemic. But a global pandemic is not out of the question in today’s modern world. Overcrowding, urbanisation, global transport, simultaneous outbreaks of animal influenza and insufficient supply of influenza vaccines could all contribute to an outbreak any time soon. The WHO even estimates that if a pandemic were to occur today, influenza would cause 2-7.4 million deaths globally – health-care systems would be rapidly overburdened, economies strained, and social order disrupted. All it would take is for the influenza virus to mutate into a strain no one has any immunity towards, which in combination with these modern-day conditions would facilitate the spread of the influenza pandemic.


Conclusion
Currently, the world is not equipped to deal with a influenza pandemic, and if it were to occur we would see devastating results. Even though a person can ‘protect’ themselves with an influenza vaccine and prevent themselves from becoming infected, the high mutation rate and incidence of antigenic shift allows new strains of influenza virus to constantly emerge and threaten to infect the population. This seemingly harmless virus is currently both treatable and preventable, but if we remain complacent about it for much longer, it might soon be uncontrollable like HIV.