May 7, 2021

I, Science

The science magazine of Imperial College

As a potential threat to the end of humanity pandemics seem popular candidates, in Hollywood at least. The emergence of new diseases is often accompanied by media frenzy and widespread fear. In Hollywood films, the disease is often the consequence of human manipulation and conveniently has symptoms which provide a commentary on the nature of man. In reality, pandemics are almost always new or mutated diseases to which there is no global immunity. Last year, swine flu was the latest pandemic to capture our headlines. Fortunately for us, swine flu was much less lethal than seasonal flu but throughout history there have been pandemics which have had huge death tolls.

The history of pandemics

We are aware of pandemics from a very early age. Primary school children learn about the bubonic plague, often under its more sinister pseudonym The Black Death.  They even unwittingly make reference to it when reciting playground favourite, ‘Ring a Ring o’ Roses’.  It is no wonder that this pandemic has made such an impact on our culture; the Black Death was one of the deadliest in human history. This outbreak is estimated to have killed up to 60% of the European population.

The plague is thought to have been carried from Asia to Europe by fleas residing on the black rats that were familiar, but uninvited, passengers on merchant ships. There was no natural immunity to the bubonic plague in Europe resulting in the high death toll. The Black Death was at its peak in Europe in the mid 14th century, however the first instance of bubonic plague can be traced as far back as the 6th Century AD when it is estimated to have killed 40% of the population of Constantinople.

International shipping was responsible for the spread of the bubonic plague and an increasing reliance on worldwide trade is thought to have caused a series of cholera pandemics in the 19th century. Cholera was, and still is, endemic in much of Asia. However, on at least seven separate occasions new strains have spread along trade routes causing worldwide pandemics.

20th Century Pandemics: Viruses

The medical and sanitary advancements of the 19th and 20th centuries reduced the risk of bacterial pandemics. A viral pandemic is now our greatest threat, in particular a highly infectious virus that is prone to mutations and capable of transspecies infection; specifically influenza. Influenza viruses are classified into three types: A, B and C. All influenza viruses change gradually through random mutation resulting in an epidemic every few years. Influenza A viruses may also change abruptly leading to a new subtype which may have the potential to cause a pandemic.

There have been three major influenza pandemics in the 20th century. The first, and worst, started in 1918; the ‘Spanish Flu’ pandemic. The disease had a very high mortality rate and spread across the world with breathtaking speed infecting a fifth of the world’s population and killing more than World War 1. Spanish Flu is unlikely to have originated in Spain, it simply received greater attention there than other European nations involved in World War 1. While the origin of Spanish Flu is unknown, the virus has been identified as H1N1, a variant of which was responsible for the 2009 swine flu pandemic.

Are we all going to die of a horrible disease?

Medicine continues to make advancements at breathtaking speeds and diseases which were once feared are now all but eradicated through vaccination. However, there are aspects of modern life which can exacerbate the spread of pandemics. We exist in global times and the world is more interconnected than ever before. As was apparent with swine flu, when a pandemic emerges, its spread is now exceptionally rapid.  This globalisation can go some way to protect us; immunity can now exist at the worldwide level. Zoonosis, where a disease gains the ability to infect more than its original host species, is now a great concern. Animal to human zoonosis is thought to have been responsible for the recent outbreaks of avian flu and swine flu.

Influenza is, at present, the most likely candidate for the next pandemic however there is also worry of a resurgence of bacterial pandemics as antibiotic resistance increases. The World Health Organisation (WHO) estimates that a new pandemic could result in 7.4 million deaths. If the pandemic became severe we could also expect shortage of vaccines, antivirals and antibiotics; strained and overcrowded medical facilities; and significant shortages of personnel resulting in reduced community services and economic instability.

If that all sounds a little bleak, at least ‘unusual’ strains will be detected immediately by WHO global surveillance. Or you might take comfort in the government’s preparedness strategy. Reassured? I’m not sure I am, but after the false starts of SARS and swine flu a real pandemic might give the media something to look forward to.