The festive season is in full swing, and all the while, the COVID-19 pandemic still looms in the background, threatening to dominate conversation over the Christmas period.
There has never been a better time to brush up on the correct epidemiology and pathology terms. Using the right terminology and having a firm grasp of the science behind the pandemic will only further your cause of having more educated and well-read dinner conversations that are sure to impress everyone at Christmas lunch.
This short guide to discussing pandemics during the festive season will work to define the biology of viruses, explore the emergence of coronaviruses and focus on the novel coronavirus SARS-CoV-2. It will explore how pandemics are created, what communicable diseases are, the meaning of the basic and effective reproduction numbers (R0 and R), how mutations occur and what on earth spike proteins are. Lastly, described will be the basics of rapid antigen tests, antibody tests and PCR tests, as well as genomic sequencing.
In this article we discuss:
2. Coronaviruses as their own kind
5. How fast a disease can spread
6. Mutations and spike proteins
7. How we can detect viral infections
Viruses are infectious agents that are considered neither living nor dead, as they cannot replicate on their own, unlike bacteria and other disease-causing nasties. They are too small to be seen through a microscope and vary between 20 and 250 nanometres in diameter – smaller than the cells in your body.
Coronaviruses are a group of RNA viruses that can be responsible for many respiratory tract infections in mammals and birds. The first human coronavirus was identified in 1965 and caused an illness regarded as the common cold. In 2003, the coronavirus SARS-CoV caused the first 21st century pandemic with the illness of severe acute respiratory syndrome (SARS), followed by a MERS outbreak in 2012 in the Middle East caused by the MERS-CoV virus. Later, COVID-19 was the name given to the illness caused by the SARS-CoV-2 virus, which first emerged in December of 2019.
Evidence suggests that SARS-CoV-2 is a zoonotic disease, meaning that it is an infectious agent that has jumped from animal to human hosts. In this instance, the animal is believed to have been a bat. Bats are considered high-risk viral reservoirs, meaning that they are more likely to carry dangerous viruses than other animals.
COVID-19 is a communicable disease, meaning that it is an illness that can spread from one person to another at a rapid pace. Viruses such can SARS-CoV-2 are able to manifest as respiratory diseases by existing in tiny water or mucous droplets which are spread through the air when someone sneezes or coughs. Hence, small outbreaks of communicable disease can quickly turn into epidemics, and in turn, pandemics. An epidemic is defined as a sudden outbreak of a disease in a certain location, whereas a pandemic is the sudden outbreak of a disease in several different countries or continents. As a consequence of international air travel, the COVID-19 outbreak grew so quickly that it was declared a global pandemic on the 11th of March 2020.
What determines how fast an outbreak can grow is the virus’ basic reproductive number R0, as well as its effective reproductive number R. Both these numbers reflect how many individuals one person with the SARS-CoV-2 virus can spread COVID-19 to during their infectious period, with a slight difference. R0 is the number when there is no immunity, vaccination or deliberate interventions to disease transmission in the population. R on the other hand is how many people the virus can spread to when there is some level of immunity and disease prevention actions, such as implementing social distancing and wearing face masks, in the population.
Like other viruses, SARS-CoV-2 can mutate. This occurs when the virus is being replicated in its host cells and a piece of RNA is changed in the process. Mutations occur by chance, and although often minor can work in the virus’ favour by allowing it to be more infectious or deadly. Spike proteins are tools that viruses, including the SARS-CoV-2 virus, use to enter host cells. These proteins can mutate, which may allow them to better evade our immune system’s defences.
Currently, there are two ways to test for the presence of a SARS-CoV-2 infection in an individual. These are called rapid antigen tests and polymerase chain reaction (PCR) tests.
Rapid antigen tests work by detecting specific proteins of the virus but are less accurate than PCR tests, which detect the presence of nucleic acids of the SARS-CoV-2 virus. Both involve the insertion of a swab into both nostrils (and in the case of a PCR test, the back of the throat). These are regions that contain mucus membranes where the virus may be residing or has been coughed up to.
In contrast, an antibody test is a blood test that can determine whether someone has been previously exposed to or vaccinated against the SARS-CoV-2 virus by identifying antibodies produced in an immune response against the COVID-19 disease. Finally, genome sequencing allows for the comparison of viral genomic sequences between cases to identify the source of infection as the virus slightly alters its RNA sequence when it moves from person to person.
This short guide for discussing the pandemic during the festive season gives a refreshing, simple take on the basics of the science behind the rise of SARS-CoV-2. Understanding how viruses function, how communicable diseases spread and how we test for them is essential in providing context for topical everyday conversations, news articles and policy changes, for instance, and more broadly for how we live our day-to-day lives in the world, we find ourselves in today.
by Sophie Sjostrom, study for a Master of Public Health, University of Melbourne and London Agency’s newest team member.
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