Things You Need To Know About A Pandemic
Difference between Outbreak, Epidemic and a Pandemic
The outbreak is usually small but unusual. When COVID19 first started in Wuhan, China, it was just an outbreak of a new type of coronavirus that caused pneumonia. A small but unusual number of pneumonia cases were reported and later it spread across the whole of China.
When an outbreak starts to spread across a much larger geographical area, it is an epidemic. When the pneumonia cases caused by a new type of coronavirus, later named as SARS-CoV-2, were found outside Wuhan, it is no longer an outbreak but COVID19 epidemic.
When the epidemic starts to spread to different countries and different parts of the world, it is called a pandemic, which is international and out of control. The World Health Organization (WHO) declared COVID19 a pandemic on 11 March 2020. When a small outbreak grew up to a pandemic level, it spreads throughout the world exponentially.
The Exponential Growth of a Pandemic
If you are unaware of what is exponential growth, let me explain it to you by a simple example. Imagine you are sitting on a seat in the highest level of the conference hall of BMICH. Suddenly, a water pipe running on the roof starts to leak a drop. In the next minute, 2 drops fall. In the next minute, 4 drops fall and so on. How much time do you think you will have until the water gets filled to your level (seat)? Hours? Days? Weeks? You will have nearly thirty minutes. And that is exponential growth. When something bad grows exponentially, it is worst. Remember, the first 100,000 global COVID19 confirmed cases took 67 days, second 100,000 cases took 11 days, third 100,000 days took 4 days and fourth 100,000 days took only 2 days. However, we may not able to stop or change the exponential behaviour of a pandemic, but we can flatten the curve!
What is ‘flatten the curve’?
Any pandemic grows exponentially, reaches to a peak and dies gradually.
Both red and blue curves above show the behaviour of a pandemic. The red-curve indicates a much higher number of infected patients at a given time. When a pandemic reaches its peak, the number of patients becomes overwhelmed. Whereas blue-curve shows a much flattened and controlled behaviour of a pandemic which may lie for a longer period but the number of patients at a given time does not exceed the finite health resources (dotted line). In the case of COVID19, social distancing, washing hands, staying at homes, working from homes, avoiding public gatherings, many other various health-protective measures and also any government interventions such as airport and schools closures, curfews, lock-downs etc. may help to get red-curve to a blue-curve which will give health officials, front-line medics, police, government etc. a much longer time to prepare and respond. More prepared and timed responses cause a lower case fatality rate.
Case Fatality Rate (CFR)
In epidemiology, Case Fatality Rate (CFR) is a measure of the severity of a disease that causes death. It is expressed as a ratio of death due to a particular disease to the total number of infected persons from the same disease.
CFR is usually a moving target with the pandemic getting spread. As of 1st April 2020, global CFR of COVID19 stands at 4.92%, i.e. nearly 5 of every 100 infected people die due to COVID19.
However, CFR does not necessarily reflect the severity of death due to a disease, because the denominator represents the number of confirmed cases but not the total cases. The number of total cases in a population is always greater than that of confirmed cases because everybody who got infected with the virus has not been tested.
Incubation Period
The incubation period of a virus is the period between the time of exposure to the virus and beginning to show symptoms of the disease. A study shows, the most probable incubation period of COVID-19 is around 5 days but it can range between 5 to 14 days. For some people, this period could be longer than 14 days; for a 70-year-old Chinese man, it had taken 27 days to show symptoms of COVID-19 after exposure to the virus.
When compared with recent pandemics, COVID-19 shows a much longer incubation period which is why it is rapidly spreading across the world. A case study shows that, during the incubation period of 14 days, COVID-19 can get spread from one to another (asymptotic transmission).
Reproduction Number (R0)
Epidemiologists and scientists use a special number known as reproduction number (R-naught) to measure how contagious a virus is. Different studies show COVID-19 has an R0 value of about 2.5, i.e. an infected person can give the virus to at least another 2 persons in the population. Each of 2 persons spread the virus to another 4 persons and so on.
When compared to diseases like Measles which has an R0 value of 16, COVID-19 is not high contagious but if no interventions are made it can spread very rapidly.
