Squiz Shortcuts – Infectious Diseases
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As the world braces for the impact of COVID-19, we’re going to take a look back at some of the big infectious disease outbreaks of the past. Where they started, their devastating mortality rate, and how they were eventually contained.
What’s the difference between an epidemic and a pandemic?
That really comes down to size. An epidemic is an outbreak of disease that registers a rise in the number of cases beyond what is normally expected in a geographical area. That becomes a pandemic when it has spread across many countries. And with COVID-19 now in 200 countries and territories around the world, it’s officially a pandemic.
Can any type of disease become a pandemic?
Pandemic outbreaks can be bacterial like cholera and the bubonic plague, or viral like influenza or a severe acute respiratory syndrome-associated coronavirus, like COVID-19. And they start and spread in different ways.
What makes an infection, or disease reach that point where it starts to spread globally?
A perfect storm of conditions: it’s something that is highly infectious, it spreads easily from human to human, and has a comparably high mortality rate. Add that to delays in recognising an outbreak, especially if it’s something we haven’t seen before, problems with testing for the disease, and delays in adequately isolating infected patients – and there isn’t a vaccine. Put together, a global outbreak can happen with devastating health, economic and social impacts.
SECTION 2 – Examples
What was smallpox?
Smallpox holds the record as the world’s most deadly infectious disease. It was characterised by a pretty nasty rash of fluid-filled bumps all over the body. The first cases of smallpox are thought to date back to the Egyptian Empire in the 3rd century BC. And before it officials said it was eradicated in 1980, it was estimated to have killed around 500 million people in the last 100 years of its existence. Throughout history it’s had both epidemic outbreaks and pandemic outbreaks, and it’s mortality rate was around 20-30% at times. The last naturally occurring case of Smallpox was diagnosed in October 1977. There was a huge concerted vaccination push from the World Health Organisation that started in the 1960s. Its thought that the first vaccine against it was actually developed in 1796… over 160 years earlier. Dr Edward Jenner in the UK discovered that immunity to smallpox could be brought about by inoculating a person with material from a cowpox lesion. He called the material used for inoculation ‘vaccine’ which comes from the root word ‘vacca’, which is Latin for cow.
What was the Spanish flu?
The Spanish flu infected about a quarter of the world’s population in the years between 1918 and 1920. It’s a bit unfair on Spain, this one. The first cases were actually reported among US troops towards the end of WWI. Their mass movement is believed to have spread of the disease. Wartime censors suppressed reporting of deaths from this flu in Germany, the UK, France and the US in an attempt to keep morale high. However, Spain, which remained neutral during the war, reported deaths there and that saw the outbreak become known as the ‘Spanish Flu’ because it appear as if it came from there.
How lethal was the Spanish flu?
It had a mortality rate of around 2.5%, and the estimated total death toll is between 17 million and 100 million. It spread around the world and was a further devastating blow to many countries struggling to come out of the trauma of WWI.
And what eventually caused it to stop? Did they develop a vaccine for this one too?
After striking the world’s populations in two big waves, new cases of the Spanish Flu dropped off significantly. There are various theories to why this was the case – but a commonly accepted explanation is that during the second wave in 1918, the virus mutated into a less lethal strain – which is a common trait in influenza viruses after a long period of time.
What is HIV/AIDS?
Human immunodeficiency viruses, or HIV, are best known as the strain of viruses that cause acquired immunodeficiency syndrome, or AIDS. Between the time that AIDS was first identified in the early 1980s and now, the disease has caused an estimated 35 million deaths around the world.
And it’s still considered a pandemic?
Yep, and that’s because it continues to spread around the world, with current infections largely concentrated in Sub-Saharan Africa. While there are records of early cases of HIV cases throughout the mid-20th century, known cases didn’t spike until the 1980s, when it spread to the West, where it became an epidemic as it spread largely throughout gay communities in the US, as well as intravenous drug users. The fact that HIV/AIDS disproportionately hit marginalised communities at first meant that authorities were slow to act.
SECTION 3 – Coronaviruses
What is a coronavirus?
Coronavirus is a group of viruses – ranging from the common cold to more severe respiratory illnesses. The term originates from the corona, or crown, of surface proteins that the virus uses to penetrate the cells of infected people.
How did Severe Acute Respiratory Syndrome, or SARS, start?
SARS is a similar virus to COVID-19. It originated in China in the early 2000s, and was thought to have originated in bats, and then made its way to being passed onto humans. There were just over 8,000 cases diagnosed between late 2002 and mid-2003 and 774 people died, and it had a particularly high mortality rate of 9.6%. It was considered an epidemic, not a pandemic. There wasn’t a global spread – the majority of cases were in mainland China and Hong Kong in people aged over 65yo. It did however, have a mortality rate of 9.6%. While there were issues with China not alerting the WHO of the outbreak for the first three months, once they did, a global threat was announced, travel restrictions were put in place, and the outbreak contained.
What about MERS?
Middle East respiratory syndrome was also known as camel flu, although it is a coronavirus that was first reported in 2012. It was also believed to have started with bats but the transmission to humans was believed to have happened via camels. Just under 2000 cases have been reported in the last three years and it’s mortality is about one-third of diagnosed cases.
What about COVID-19?
To start with COVID-19 is the name designated to this virus by the World Health Organisation. The COV in the name is shorthand for coronavirus, and it’s ID number is 19 from the year it started. On the 31st December the World Health Organisation was notified by Chinese officials of a new illness, fast forward to the 11th of March, and it was declared a pandemic. What we’ve seen with Covid-19 is all the hallmarks of a pandemic – the struggle at the start to identify it, and then test for it as it took hold in Wuhan in China and surrounding cities. And then there are the issues with testing for it, which is now happening quite efficiently and the development of a vaccine, which will take until the start of 2021 at the earliest. Iin the meantime, it’s spread to almost every corner of the planet. The US and Australia were two of the first nations to start screening people coming off flights from Wuhan. Travel bans were then put in place, and now our border is closed to all foreign travellers. The pace of the spread of COVID-19 has been concerning to experts. And there’s a long way to go to handle the cases of people with cases of the virus, stop the spread and pick up the pieces of badly damaged economies around the world. Officials are calling it a once-in-a-hundred-years event.