What is coronavirus| History|Types |Stages| Prevention

Corona: Corona was named by a group of virologists in 1960s. This word Coronavirus is taken from the Latin language corona, meaning “crown” or “halo”. Under two-dimensional transmission electron microscope, characteristic appearance resembling crown or a solar corona around the virions (virus particles) is seen, because surface is covered with club-shaped protein spikes. Mammals and birds are affected by this.

History: Human coronaviruses such as Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS) coronavirus, endemic human coronaviruses (HCoV) can survive on inanimate surfaces like metal, plastic or glass till 9 days.

Coronavirus disease: Coronavirus disease (COVID-19) is a contagious disease caused by a recently discovered coronavirus. The virus is of the size 125 nm and is bigger than influenza, MERS and SARS viruses.

Symptoms: Symptoms include- dry cough, fever, fatigue, sore throat, nasal congestion and diarrhoea. They can be mild to moderate.  Most vulnerable ones are- People having old age or those with underlying medical problems such as diabetes, cardiovascular disease, , chronic respiratory disease or cancer.

Recent study showed that (SARS-CoV-2) targets the alveolar epithelial type II cells which would function as a reservoir for viral invasion in the lung tissue.

Types:

The family of Coronaviruses is Coronaviridae and subfamily is Coronavirinae.

Different types of human coronaviruses, presently seven, have potential to infect humans which can result in different severity and also its spread.

Common types include:

NL63 (alpha coronavirus)

229E (alpha coronavirus)

HKU1 (beta coronavirus)

OC43 (beta coronavirus)

There are four stages of coronavirus:

Stage 1- This stage is imported cases.  These cases are the people who have travelled abroad where there were confirmed cases of the virus and have returned back. First stage is in single or double digits in 1^st week.

Stage 2- This stage is local transmission and cases are found in few hundreds. If a person gets infected with coronavirus we can trace the person who passed the infection. They can be someone who have travelled aboard or came in contact with someone else who has a positive travel history. The person most likely got infected and then pass it on. This tracing of the infection is called contact tracing and is very helpful to stop its spread.

Stage 3- Third stage is community spread. Due to infected people coming in contact with local people and others. This results in 100s to 1000s of cases. This stage should be avoided beacuse virus cannot be traced back to a certain person.

Stage 4- In fourth stage these numbers increase in geometric progression in several thousands, it results in huge positive cases and large fatalities.  The losses are much in 4^th stage and also 3^rd stage.  The chain needs to be broken and it should be seen that the curve does not progress and it flattens.

This is the pattern which is observed in China, Italy and Spain etc. Focus should be there on lockdown, curfew, more testing.

What to do if symptomatic:

The best way is to be well informed about this disease.

• Stay home when you are sick
• Wash hands or use an alcohol based rub frequently and do not touch your face.  
• It can also be spread by touching something an infected person has touched. The infection spreads primarily by droplets of saliva or discharge from nose by coughing or sneezing, so precautions should be taken (e.g. by coughing into a flexed elbow).
• Movement should be limited in the community
• Limit visitors

Dr. Asma Naz

She is Ph.D. holder in Agriculture (Plant Pathology and Nematology).