Covid-19 at a glance

Covid-19

Overview:
Corona Virus Disease (Covid-19) is an infectious disease highly contagious in nature caused by newly emerged member of coronal virus family. Previously corona virus known to cause common cold, SARS and MERS disease. It was believed to originated from wholesale Sea food market of Wuhan , capital city Hubei province in the People's Republic of China. First case was reported in 31st December 2019.

Timeline of disease:
Dec 31, 2019: WHO is informed of cases of pneumonia of unknown etiology detected in Wuhan city China.
Jan 11, 2020: Report of first known death due to an illness caused by novel coronavirus.
Jan 30, 2020: the WHO declares "Public health emergency of international concern".
Feb 7, 2020: Chinese medic who tried to warn about the virus, dies from Novel corona virus disease.

Feb11, 2020: WHO announced a name for new coronavirus disease COVID-19.
Feb 29, 2020: US reports its first Covid-19 death.
Mar 3, 2020: WHO warns of severe and mounting disruption of global supply of PPEs.
Mar 11, 2020: WHO declares Covid-19 a pandemic.
Mar 23, 2020: WHO's director general says Covid-19 pandemic is accelerating.
Mar 24, 2020: After a week with almost no new cases, China announes that Wuhan lockdown will be partially lifted, April 8th Tokyo olympics and paralympics postponed until 2021.


Incubation Period: generally disease forecast within 2-14 days(5- 6 days avg. )

Spread by: Droplet infection (cough and sneeze), surfaces (table, desk etc), hand shaking.

Symptoms :
Covid-19 affects different people in different ways. Most infected people will develop mild to moderate illness and recover without hospitalization.
Most common symptoms:

• Fever
• Dry cough
• Tiredness

Less common symptoms:

• Aches and pains
• Sore throat 
• Diarrhea
• Conjunctivitis 
• Headache
• Loss of taste or smell
• A rash on skin, or discoloration of finger or toes.

Serious symptoms:

• Difficulty breathing or shortness of breath
• Chest pain or pressure
• Loss of speech or movement

Population at risk:

• Recent contact of covid-19 confirmed case
• Immunocompromised patients
• Patient with chronic disorders bronchial asthama, diabetes, cardiovascular disorders
• Elderly (60+age)
• Health care personnel treating covid-19 confirmed cases

Prevention:

• Wash your hand frequently by using soaps or alcohol base hand sanitizer.
• Avoid touching your eyes, nose and mouth
• Avoid Crowded place public gathering
• maintain social distance of at least 1 metre.
• Cover your mouth cough/ sneeze with tissue/ bend of elbow 
• Contact by call to  nearest hospital if you have any symptoms don't go without call to any hospital.
• wearing mask while travelling (better to avoid international travelling)
• No handshake, use touchless greeting(Namaste)
• Say no to panic , say yes to precaution

Isolation and Quarantine:

Quarantine: The limitation of freedom of movement of such well persons or domestic animals exposed to communicable disease for a period of time not longer than the longest usual incubation period of the disease, in such manner as to prevent effective contact with those not so exposed.

purpose of quarantine is to prevent the transport of infection across national boundaries.

Duration of quarantine is 14 days (may be extend to 21 days in some cases)

Isolation: Separation, for the period of communicability of infected persons or animals from others in such places and under such conditions, as to prevent or limit the direct or indirect transmission of the infectious agent from those infected to those who are susceptible, or who may spread the agent to others.

Purpose of isolation is to limit the spread of the disease in the community

Duration of isolation is as long as the disease remains communicable i.e. it may be short, same or more than of incubation period.

When and how to wear medical masks to protect against coronavirus?

·         If you are healthy, you only need to wear a mask if you are taking care of a person with COVID-19.

·         Wear a mask if you are coughing or sneezing.

·         Masks are effective only when used in combination with frequent hand-cleaning with alcohol-based hand rub or soap and water.

·         If you wear a mask, then you must know how to use it and dispose of it properly.

Methods of Using mask:

·         Before putting on a mask, clean hands with alcohol-based hand rub or soap and water.

·         Cover mouth and nose with mask and make sure there are no gaps between your face and the mask.

·         Avoid touching the mask while using it; if you do, clean your hands with alcohol-based hand rub or soap and water.

·         Replace the mask with a new one as soon as it is damp and do not re-use single-use masks.

·         To remove the mask: remove it from behind (do not touch the front of mask); discard immediately in a closed bin; clean hands with alcohol-based hand rub or soap and water.

Precaution only for Health care personnel : 

use Personal Protective Equipment as per WHO or Medical Council guidelines.

About Virus: Evolution

Seven strains of corona virus(CoV) that infect humans have been identified. These cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV).

Harmless strain: Serotype229E, Serotype OC43,Serotype NL63, Serotype HUK1 ,these cause symptoms of the common cold,and rarely causes pneumonia.

Dangerous strain: these are known to cause more severe disease.These are:
1.SARS-CoV which causes Severe Respiratory Syndrome(SARS)
2.MERS-CoV was that causes Middle East Respiratory Sundrome (MERS)
3.SARS-CoV2 that  causes corona virus disease (Covid19)

SARS-CoV2 is closely related( with 88% identity ) to two bat derived SARS-like corona viruses (bat-SL-CoV-2C45 and bat-SL-CoVZXC21) collected in 2018 in Zhoushan, eastern China.
It has 79% genetic affinity with SARS-CoV, 50% with MERS-CoV.
The SARS-CoV2 receptor-binding domain structure which allows a virus to latch on to and enter a cell is similar to SARS-CoV, despite of amino acid variation atsome key residues.
Little is known about SARS-CoV provide clues to its behaviour and abiltiy to infect.

Zoonotic origin: mutated strain might came from Bats, Snake, Pangolin, civet cats, camels

Structure of Corona Virus:

It is a single stranded  positive (SS+) sense  RNA virus. Virus has outer Spike Glycoproteins (Protein gai), M-Protein, Hemagglutinin- esterase dimer(HE), an envelope, RNA and N Protein and E protein.

fig: structure of Corona virus(Sars-CoV2)

Pathogenesis: 

Unique feature is that this virus causes both upper respiratory tract infection and lower respiratory tract infection.

Virus attaches to specific cellular receptor via the Spike protein to ACE-II receptor of Type-2 pneumocytes. 

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Transformational change, leading to fusion between the viral and cell membrane

                                                ↑

Release of nucleocapsid into the cell then transcription and translation occur

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Alternation of host cell DNA and production of protein and enzymes(RNA dependent RNA polymerase)  leads to alternation of cell function of respiratory tract

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Sudden release of excess immune mediators like cytokines and chemokines (IL-1, IL-6, IL-7, IL-8, IL-9, IL-10 and TNF-alfa)

Increased Acute Phase reactants (ESR, CRP, Procalcitonin)

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 May lead to death due to complications caused by "cytokine storm syndrome". Such as Severe Acute Respiratory Syndrome) or Fulminant Myocarditis.

Investigation :
Principle:
Since it is a viral disease, Nucleotide sequence can be detected by PCR method. and antibodies against virus can be detected by RDT. Virus culture is not done for precaution purpose. several other clinical investigation are done beside virological tests. 

Specimen collection: Nasopharyngeal and throat swab for PCR

And blood sample from finger pulp for RDT

A. Virological test. 

1. Real time  reverse transcription Polymerase Chain Reaction (rRT-PCR): confirmatory test
2. Rapid diagnostic test (RDT): screening test

B. Radiology and imaging:

1. CT-chest: Ground glass opacity with or without consolidation, bilateral peripheral involvement especially lower lobe. These findings can be found even before onset of symptoms but  not specific for covid-19.
2. Chest x-ray: for any sign of consolidation and secondary bacterial infection. 

C. Others test: for treatment purpose and to support the diagnosis.

1. WBC count: shows leukopenia (<4000/mm³  ) more common / leukocytosis
2. Lymphocyte count : shows lymphopenia (most common findings)
3. Serum LDH level:  Increased S. LDH , due to affinity of cytokines for cardiac tissue and hepatic tissue.
4. Ferritin level: Increased, an early finding
5. Liver enzymes(aminotransferase) : Increased ALT and AST
6. Acute phase Reactant: ↑ ESR, ↑D-dimer, ↑Procalcitonin

Treatment:
No vaccine is available at present. many vaccines are under clinical trials.
There is no certain Protocol  postulated by WHO for the treatment of Covid-19 cases.
 . So  only symptomatic treatment is given till date.

 Doctors, nurses and hospital staff who are directly handling the patient must use PPE as per guidelines.

• Isolate the patient to prevent infection to others
• Only supporting treatment.
• Maintain airway breathing, circulation
• Antipyretic for temperature control.
• Oxygenation for shortness of breath
• Ventilation is required if (pCo2<50%)
• correction of electrolyte imbalance
• Beside these some antivirals like Remdesivir is approved by US FDA. ivermectin+ doxycycline combination therapy in Bangladesh. WHO banned on clinical trial upon Antimalarial anti-inflammatory  Hydroxychloroquine and antiviral Ritonavir. But there is no strong clinical trials to support those regimen till now. Because those research has small  sample size. 
• For moderate to severe COVID-19 cases: 
• Plasma therapy: plasma extracted form the cured covid-19 patient has being showing some sucess in treatment  for the severe covid-19 cases. 1 bag FFP (200ml)Stat @20 drops per min
• Inj. Remdesivir -200mg stat over 2 hr stat & Inj remdesivir -100 mg over 1 hr daily for 4 days.
  
• Factor Xa inhibitors- like rivaroxaban and Apixaban : These agents prevents thromboembolism and hence decreases the mortality in critically ill covid-19 patients. 
• Inj. Dexomethasone to treat severe covid-19 patients, this drug showing better outcone.

Discharge criteria of Covid-19 patient:

Clinical:

• Afebrile >72 hours without antipyretics
• Improvement in respiratiory symptoms/signs
• More than 7 days since the onset of symptoms

Laboratory:

• Negative RT-PCR from at least two specimens collected ≤ 24 hrs apart

REFERENCES:

• World Health Organization ,who.int
• Nepal Medical Council, nmc.org.np
• Parks textbook of preventive and social medicine 23rd edition
• Review of medical microbiology and immunology 12 edition by Warren Levinson 
• Medescape.com
• Director General Health service of Bangladesh, Www. Dghs.gov.bd/national COVID guidline