Alone you are strong, together you are stronger (you believe or not, COVID19 does)

Dr. Jubayer Rahman, USA

This is true that COVID19 virus follows same theory to infect millions and millions of people around the globe. COVID19 is extremely different from other COVIDs which people might have experienced at least at the level of transmission from human to human. 

People experience normal flu-like symptoms with other COVIDs and still can go for work. However, when COVID19 emerged (does not mean other COVIDs are gone), immediately took the lead and surpassed all the previous records in the rate of transmission. 

Second, elderly people or people with some underlying conditions get seriously ill by COVID19. Because of our curiosity, one question centered ‘why the transmission is so fast’? and ‘why only a group of people (elderly) heavily hit by this virus?

A group of scientists from Germany and UK performed this recent study among 9 patients of COVID19 cases to understand one key question why this virus is so different than other COVIDs in terms of infection, pathogenicity and transmission. All 9 patients had mild symptoms and didn’t develop severe lung pneumonia-like symptoms. This is just published in NATURE (https://doi.org/10.1038/s41586-020-2196-x).

Unlike other COVIDs, COVID19 virus particles don’t need to go deeper into the respiratory tract to cause infection. Other COVIDs need to go to the lower respiratory tract to be able to cause infection. However, COVID19 colonize at a high density in the upper respiratory tract even before going to the lower respiratory tract. On top of that COVID19 replication 4-7 fold more than other COVIDs. 

So, two key factors: extremely higher rate of replication and ability to colonize in the upper respiratory area explain why person infected with COVID-19 can be easily shedding this virus into the environment or to another person coming in close contact. It is just million times more doses people are exposed, therefore either carrying it to the next person or develop disease symptoms. 

This research highlighted one unexpected observation in one patient who got two different COVID19 as shown in samples from two different places from the body. They observed one mutation in the COVID19 isolated from the same person as well as original COVID19 like other patients had. This is also alarming how fast this virus may acquire mutation. 

To be able to establish disease in a person, virus needs to be won against human defense system, which is very delicate and organized at different layers. COVID19 has been successful in breaking this defense because of the power of replication. When the doses of viral particle are so high human immune system especially people with suboptimal immunity get breached and virus gain full control over the general immunity. 

This study also checked antibody against COVID-19 in those patients and only found detectable levels 7-14 days post-infection. Because of higher replication rate in the upper respiratory tract, nasal swab is so successful for the diagnosis of COVID19. So the simple math that you can obviously imagine, when virus multiplication is so rapid, shedding of virus particle would be also higher. Everything you could multiply by a factor of millions (x106). Due to this nature, millions and millions of people are getting this virus. So this is really the fact ‘alone you are strong but together you are stronger’.

Reference: Virological assessment of hospitalized patients with COVID-2019, Roman Wolfel et al, Nature (2020).