CORONA VIRUS, A BRIEF PRESENTATION

Coronaviruses are a gaggle of related RNA viruses that cause diseases in mammals and birds. In humans, these viruses cause tract infections which will range from mild to lethal. Mild illnesses include some cases of the cold, while more lethal varieties can cause SARS, MERS, and COVID-19.

 

MORPHOLOGY

• Coronaviruses are enveloped carrying petal or club shaped or crownlike peplomer spikes giving appearance of solar corona.

• They are spherical or pleomorphic medium sized about 120-160nm.

• They posses linear positive-sense SSRNA of 26 to 32 Kbp size ,largest among the non-segmented RNA viruses.

CLASSIFICATION

They belongs to family coronaviridae. Coronaviridae family contains two sub families :

• Corona virinae    • Toro virinae

The former has been grouped into 4 genera : alpha coronaviruses and beta coronaviruses which infects mammals and gamma coronaviruses and delta coronaviruses which primarily infects birds.

HUMAN CORONA VIRUSES

There are seven recognised coronaviruses that are known to cause human infections .

They are :

1. Human coronavirus 229E

2. Human coronavirus NL63

3. Human coronavirus OC43

4. Human coronavirus HKU1

5. SARS-CoV ( Severe Acute Respiratory Syndrome Coronaviruses)

6. MERS-CoV (Middle East Respiratory Syndrome)

7. COVID-19

Incubation period varies from 2 to 5 days but in newly recognized coronavirus the incubation period can be as long as 14 days.

Mortality rate of different coronaviruses.

• COVID-19 :- ~ 2-4 %

• MERS-CoV :- ~ 34.4%

• SARS-CoV :- ~ 9.6%

RESERVOIR AND TRANSMISSION OF COVID-19

• The original animal reservoir of COVID-19 is Bats

• The risk of being infected by a patient with coronavirus disease 2019 can occur in both symptomatic and non symptomatic phases.

• Coronaviruses are most commonly spread from an infected person by:

1. Coughing and sneezing

2. Close personal contact such as touching or shaking hands.

3. Touching a surface or object with the virus on it and then touching your mouth ,nose or eyes before washing the hands.

4. Foecal contamination.

• Cell Reservoir for COVID-19 – A recent study showed that severe acute respiratory syndrome coronavirus 2 (SARS-CO2) targets the alveolar epithelia type II cells ,which would hence function as a reservoir for viral invasion in the lung tissue.

SIGN AND SYMPTOMS

• Fever

• Cough

• Shortness of breath or difficulty in breathing

• Chills

• Muscle pains

• Headache

• Sore throat

• Loss of taste or smell

HISTOLOGICAL FINDINGS

1. Cellular fibromyxoid exudates

2. Pneumocytes desquamation

3. Formation of hyaline membrane

EXAGGERATING FACTORS

Clinical and demograohic factors that may promote the progression towards severe form of covid-19

• Underlying malignance

• Presence of cardiovascular disease

• Geriatric citizens

LABORATORY DIAGNOSIS

1. SPECIMEN COLLECTION

– Nasopharyngeal swab

– Oropharyngeal swab

2. STORAGE

Place collected swabs into separate steriled tubes containing 2-3ml of viral transport media , refrigerated at 2-8°C

3. POLYMERASE CHAIN REACTION RT-

PCR enables the diagnosis of acute infection of virus. A typical RT-PCR procedure for detecting COVID-19 infection typically encompases in sequence,the following steps :

• RNA isolates from upper and lower respiratory specimen.

• RNA purification

• Reverse transcriptase of RNA to CDNA.

• CDNA amplification with real time PCR instrunment.

• Fluorescent signal detection.

Laboratory abnormalities predicting severe covid-19

• Increase in following:

1. Neutrophil count 2. Lactate dehydrogenase(LDH)

3. Alanine aminotransferase(ALT)

4. Aspartate aminotransferase(AST)

5. Total bilirubin

6. Creatinine

7. Cardiac biomarkers

8. D-dimer

9. Prothrombin time

10. Procalcitonin

11. C-reactive protein(CRP)

• Decreased in following :

1. Lymphocyte count

2. Albumin

PREVENTION AND CONTROL

There are no specific drugs or vaccine available for covid-19 infection till now. Though some control measures are there which are as follows:

• Isolation of patients.

• The virus exposed people should be quarantined.

• Travel restriction is mandatory but if it is needed then it should be done with proper precautionary measures.

• Uses of steriled gloves ,gowns , googles and face masks and respirators is must by health care workers.

• Thorough and frequent sanitising and handwash must be practiced .

• Avoid personal contact with each other . Isolate yourself and be far from crowded places.

 

Originally written by :

VIKRANT ADHIKARI

( BSC MLT 3RD YEAR , DR.BR AMBEDKAR MEDICAL COLLEGE )

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