Your Guide to COVID-19

ORIGIN

The consensus after studying the spread and the genome of the virus COVID-2019(Coronavirus diseases) is that it likely originated in a live animal market, in Wuhan, China. However, the animal reservoir of the COVID-2019 is not known, but is assumed to be bats.

SPREAD

The virus is mainly thought to spread from person to person. It is important to note that it is carried by droplets and is not airborne, thus a person can only contract the virus when he/she is in close proximity of an already affected person( about 6-feet). This makes the disease little less contagious as compared to other viral diseases. Measles is an excellent example of airborne disease. You can contract measles by inhaling the infectious virus, and being very tiny it can remain suspended in the air for a long time making it highly contagious. COVID-19 can also affect a person if he/she touches their own eyes, nose, or mouth after touching a contaminated surface.

The virus seems to be spreading in a sustained fashion and the type of spread is community spread(people have been infected with the virus in an area, including some who are not sure how or where they became infected).

From the map above, it is clear that almost all countries are affected by COVID-19 and the number of affected people keeps on increasing significantly every day. WHO has announced it to be a pandemic(worldwide spread of an infectious disease).

FATALITY

The infographic above shows that the virus is more fatal than seasonal flu and almost as deadly as measles although it is less contagious than that. As of March 3, the mortality rate of COVID-19 is 3.4% as estimated by WHO. The mortality rate is way more than seasonal flu( 0.1% or less).

Another reason for it to be so dangerous is that an increasing number of cases are taking a toll on health care systems and it is getting difficult to maintain the supplies. Secondly, we do not have any innate immunity against this strain of the virus as it is new.

The incubation period of novel coronavirus may range from 2-14 days, while the average incubation period is 5 days. This large incubation period makes the disease more dangerous, as people might be carrying the virus and spreading it to others without showing any symptoms.

The graph above shows that people above the age of 60 have a higher mortality rate. Although children can be affected by the novel coronavirus, the mortality rate is very low. This makes the biggest risk factor group to be the elderly. Moreover, according to WHO, people who are affected by coronavirus are mostly above the age of 40 or are immunocompromised individuals. Data also suggests that in 82% of cases the symptoms are relatively mild.

EFFECT

The virus has positive-strand of RNA enclosed in an envelope. On the surface of this envelope are present spikes of glycoproteins which act as keys to locks present on the cell membrane called receptors. After entering your body, the virus looks for the cell which has a compatible receptor. This makes the virus target specific as different types of cells have different receptors. For the novel coronavirus, the compatible receptors are present on the ciliary cells and goblet cells of the respiratory system. Goblet cells secrete mucus which keeps the lungs moist and protects it from pathogens, while cilia on ciliary cells beat the mucus towards the exterior of the mouth.

After entering the cell, they use cells machinery to replicate and produce new viruses of their kind, eventually leading to the cells death. The death of these cell affects our first line of defence-filling our lungs with pathogens, debris and fluid.

A case study was conducted on the effects of non-severe COVID-19, and intensity of immunological response prior to the patient's recovery. The findings were as follows.

i) Both ASCs(source of mesenchymal stem cells which are multipotent making them capable of differentiating into various cell types) and cTFH(circulating T Follicular Helper Cells- are subsets of immune cells and play an important role in pathogenesis) were found in the patient's blood before the resolution of symptoms.

ii) The emergence and rapid increase in activated CD38+HLA-DR+ T cells(exhibit a higher functional response by suppressing viral replication) before the resolution of symptoms.

iii) Lower frequency of CD16+CD14+ monocytes( associated with phagocytosis, antigen presentation, and cytokine production). Probably due to the migration of these cells from blood to the infected site.

iv) Minimal levels of cytokines and chemokines were found in this patient even in the symptomatic stage. These are signalling molecules that mediate immunological response. Excess secretion of cytokinin is termed as a cytokinin storm.

GENERAL QUESTIONS

PREVENTION

BIBLIOGRAPHY

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Francis, Matthew R. “Just How Contagious Is COVID-19? This Chart Puts It in Perspective.” Popular Science, Popular Science, 20 Feb. 2020, www.popsci.com/story/health/how-diseases-spread/.

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“Home.” World Health Organization, World Health Organization, www.who.int/.

“Infectious Diseases A-Z: Why the Measles Virus Is so Contagious.” Mayo Clinic, Mayo Foundation for Medical Education and Research, newsnetwork.mayoclinic.org/discussion/infectious-diseases-a-z-why-the-measles-virus-is-so-contagious/.

McCandless, David. “COVID-19 #CoronaVirus Infographic Datapack.” Information Is Beautiful, Information Is Beautiful, 17 Mar. 2020, informationisbeautiful.net/visualizations/covid-19-coronavirus-infographic-datapack/.

Thevarajan, Irani, et al. “Breadth of Concomitant Immune Responses Prior to Patient Recovery: a Case Report of Non-Severe COVID-19.” Nature News, Nature Publishing Group, 16 Mar. 2020, www.nature.com/articles/s41591-020-0819-2.

“Transmission of Coronavirus Disease 2019 (COVID-19).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 4 Mar. 2020, www.cdc.gov/coronavirus/2019-ncov/prepare/transmission.html.