There are many evidences that prove that basic transmission mode of virus is human to human. Also the major routes of transmission of COVID 19 are droplet and close contact but other pathways like oral etc are not known. Also the presence of COVID 19 is detected in tear as similar to SARS-CoV. Reproductive number (R0) was estimated by some studies. Based on the clinical data of patients in COVID-19 early outbreak, the mean R0 was ranging from 2.20 to 3.58, meaning that each patient has been spreading infection to 2 or 3 other people. More research will be needed in future to check out the exact RO as this is early estimation of RO. The mean incubation period is about 5 days, ranging from 1-14 days and 95% of patients are likely to experience symptoms within 12.5 days of contact. Through this analysis we can suggest that at least 14 days quarantine period require checking any patient that have mild symptoms of COVID 19 disease. However, an asymptomatic carrier was reported and the incubation period was 19 days, suggesting the complicated challenge to contain the outbreak.

Coronavirus Covid-19 Look Inside
Iqra Rehman
Iqra Rehman

CORONAVIRUS COVID-19 LOOK INSIDE

In late December 2019, in Wuhan China a lot of unexpected pneumonia cases have been reported. After some days it is identified that it is a novel corona virus that is causative agent of this pneumonia. This virus has been temporarily named as sever acute respiratory syndrome corona virus 2(SARS-CoV-2). And the relevant infected disease has been named as Corona Virus disease 2019(COVID-19) by the world health organization. Epidemic that started from china now spread all over the world. According to an analytical data there were 9720 people in china that were infected and 213 death confirmed up to January 31, 2020. According to world health organization data there were 78630 cases and 2747 death were reported and also spread to 46 other countries in world up to February 27, 2020.

 

INTRODUCTION OF CORONAVIRUS COVID-19:

 

Corona virus is highly diversified, enveloped, positive-sense, single stranded RNA viruses. There are many diseases that cause by COVID 19, like respiratory, enteric, hepatic, and neurological disorders. And the level of severity is different among human to human and although human and animal. A low percentage of respiratory infection is caused by human CoV. A mild respiratory sickness also cause by HCoV-OC43, HCoV-229E, HCoV-NL63 and HCoV-HKU1 strains.

Over the past two decades, two novel coronaviruses, severe acute respiratory syndrome CoV (SARS-CoV) and Middle East respiratory syndrome CoV (MERS-CoV), have emerged and cause severe human diseases. . During the epidemic, SARS-CoV infects more than 8000 people worldwide with nearly 800 fatalities, representing its mortality rate around 10%. Whereas MERS-CoV infected over 857 official cases and 334 deaths, making its mortality rate approximately 35%. So far, SARS-CoV-2 is the seventh member of the family of coronaviruses that infects humans.  Symptoms of COVID 19 is similar to (MERS-CoV) and (SARS-CoV) like;

           Cough

           Fatigue

           Fever

           Dyspnea

           Shortness of breath

           Sore throat

These coronaviruses have some overlapping features like pathology and pathogenesis. All these viruses cause disease in human beings.

SARS-CoV-2 STRUCTURE:

This is a novel member of coronaviruses. Due to genetic similarity in coronaviruses members and with SARS-CoV-2, it is assume that this SARS-CoV-2 originate from bat. The intermediate host that provide pathway for the transfer of virus from bat to human still unknown. We cannot say that all coronaviruses members have same genetic makeup, instead they also have some different genetic sequences, which are the reason they have some unique qualities also. The analysis of samples from seven SARS-CoV-2 infected patients suggested that SARS-CoV-2 shares 79.5% sequence identity to SARS-CoV3. Simple analysis showed that SARS-CoV-2 share 96.2% overall genome sequence identity to RaTG13, which is a short RdRp region from a bat coronavirus3. Phylogenetic analysis revealed that SARS-CoV-2 falls into the subgenus Sarbecovirus of the genus Betacoronavirus and is distinct from SARS-CoV-2.

The envelope spike (S) protein is important for coronavirus. The S protein mediates receptor binding and membrane fusion and is crucial for determining host tropism and transmission capacity. Generally, the S protein is functionally divided into the S1 domain, responsible for receptor binding, and S2 domain, responsible for cell membrane fusion. Structure analysis suggested that receptor-binding domain was composed of a core and an external subdomain. Angiotensin converting enzyme II (ACE2) was known as cell receptor for SARS-CoV. Similar to SARS-CoV, SARS-CoV-2 also uses ACE2 as an entry. Receptor in the ACE2-expressing cells, indicating SARS-CoV-2 may share the same life cycle with SARS-CoV. The biophysical and structural analysis indicated that S protein of SARS-CoV-2 binds ACE2 with approximately10- to 20- fold higher affinity than S protein of SARS-CoV. The high affinity of S protein for human ACE2 may facilitate the spread of SARS-CoV-2 in human populations. Meanwhile, SARS-CoV-2 does not use other coronavirus receptors, such as amino peptidase N and dipeptidyl peptidase 4 (DPP4) to enter cells.

 

Coronavirus Covid-19 Look Inside 1

TRANSMISSION MODE:

There are many evidences that prove that basic transmission mode of virus is human to human. Also the major routes of transmission of COVID 19 are droplet and close contact but other pathways like oral etc are not known. Also the presence of COVID 19 is detected in tear as similar to SARS-CoV. Reproductive number (R0) was estimated by some studies. Based on the clinical data of patients in COVID-19 early outbreak, the mean R0 was ranging from 2.20 to 3.58, meaning that each patient has been spreading infection to 2 or 3 other people. More research will be needed in future to check out the exact RO as this is early estimation of RO. The mean incubation period is about 5 days, ranging from 1-14 days and 95% of patients are likely to experience symptoms within 12.5 days of contact. Through this analysis we can suggest that at least 14 days quarantine period require checking any patient that have mild symptoms of COVID 19 disease. However, an asymptomatic carrier was reported and the incubation period was 19 days, suggesting the complicated challenge to contain the outbreak.

CLINICAL FEATURE:

Most case patients were 30-79 years of age32. The median age is ranging from 49 to 59 years. There were few cases in children below 15 years of age. More than half the patients were male. Nearly half the cases had one or more coexisting medical conditions, such as hypertension, diabetes and cardiovascular disease. A large cases study indicated that the case-fatality rate was elevated among those patients with coexisting medical conditions. The spectrum of clinical presentations of COVID-19 has been reported ranging from asymptomatic infection to severe respiratory failure. There are some uncommon symptoms include sputum production, headache, hemoptysis and diarrhea. Although pneumonia is present in most SARS-CoV-2 infected patients, few cases complained of pleuritic chest pain. According to the severity of symptoms, patients can be classified as mild, severe, and critical types. Mild patients had no pneumonia or mild pneumonia. Severe patients had several clinical findings, including dyspnea, respiratory frequency ≥ 30/min, blood oxygen saturation ≤ 93%, partial pressure of arterial oxygen to fraction of inspired oxygen ratio < 300, and/or lung infiltrates >50% within 24 to 48 hours. Critical patients had severe conditions, such as respiratory.

Coronavirus Covid-19 Look Inside 2

PATHOLOGY:

The pathological findings of human SARS-CoV-2 infection have been limited due to the rare number of biopsies or autopsies. In a case reported by a 50-year old man died 14 days after admission due to respiratory failure and cardiac arrest. The primary finding of biopsy at autopsy was bilateral diffuse alveolar damage with cellular fibromyxoid exudates and interstitial mononuclear inflammatory infiltrates dominated by lymphocytes. Multinucleated syncytial cells with a typical enlarged pneumocystis characterized by large nuclei, amphophilic granular cytoplasm, and prominent nucleoli were identified in the intra alveolar spaces, showing viral cytopathic-like changes. No obvious intra nuclear or intra cytoplasmic viral inclusions were identified. These pathological features show great similarities to SARS-CoV and MERS-CoV infection. In addition, liver and heart were studied. There is moderate micro vascular steatosis and mild lobular and portal activity in the liver tissue and a few interstitial mononuclear inflammatory infiltrates in the heart tissue.

DIAGANOSIS:

Although a good contact history, systemic symptoms, and radiographic changes of pneumonia make the diagnosis likely, the laboratory diagnosis is more reliable. RT-PCR is routinely used to detect causative viruses from respiratory secretions. During COVID-19 transmission events, RT-PCR has served as the primary clinical laboratory diagnostic test. Successes of these tests are very important to understand the viral kinetics and tissue tropism found in COVID-19 cases. Several specific and sensitive assays targeting RdRP, N, and E genes of the SARS-CoV-2 genome were designed to detect viral RNA in clinical specimens. Lower respiratory tract samples provide the higher viral loads. The sampling source or operation may affect RT-PCR testing results. The positive rate of RT-PCR for throat swab samples was reported to be about 60% in early stage of COVID-19. These findings suggested that the result of RT-PCR should be interpreted with caution. One study investigated the diagnostic value and consistency of chest CT compared with RT-PCR test in 1014 patients with suspected SARS-CoV-2 infection. The results suggest that the sensitivity of chest CT in suspected patients was 97% based on positive RT-PCR result and 75% based on negative RT-PCR results. These findings indicated that chest CT is a sensitive modality to detect SARS-CoV-2 infection. During the COVID-19 epidemic in China, 10567 patients were diagnosed as clinical diagnosed cases. This designation is being used in Hubei Province, where is the worst affected area in China. In these cases, no RT-PCR test was performed but diagnosis was made based on typical symptoms, exposure history, and chest CT manifestations consistent with COVID-19 pneumonia. Under these criteria, 10567 cases were diagnosed and isolated. This strategy quarantined a large number of suspected people and protected the healthy people to the most extent. Based on the experiences above, we strongly recommend that the criteria of clinical diagnosed cases based on the symptoms, exposure history and typical manifestations on chest CT imaging should be used in COVID-19 affected areas that are in shortage of RT-PCR testing kits to control the COVID-19 epidemic.

TREATMENT:

Until the diagnosis is confirmed, SARS-CoV-2 infected patients are treated in single rooms. As SARS-CoV-2 is an emerging virus, an effective antiviral treatment has not been identified. The main treatment of COVID-19 is symptomatic treatment. The antiviral drugs, including oseltamivir, ribavirin, ganciclovir, lopinavir, and ritonavir have been used in attempts to reduce viral load and to prevent the likelihood of respiratory complications in several studies. Remdesivir was reported in the treatment of a patient with COVID-19 in the United States and got an effective result. However, the efficacy of these antiviral drugs for COVID-19 needs to be verified by randomized, controlled clinical trials. The antibiotics used generally covered common pathogens and some a typical pathogens. When secondary bacterial infection occurred, medication was administered according to the results of bacterial culture and drug sensitivity. Current evidence in patients with SARS and MERS suggests that receiving corticosteroids did not have a survival benefit, but rather delayed viral clearance. Therefore, routine corticosteroids should be avoided unless they are indicated for other reason. Arbidol is used empirically in China because of its direct antiviral effect on SARS-CoV in cell culture. Chinese herbal medicine formulae are used to prevent SARS-CoV-2 infection in 23 provinces in China.

Coronavirus Covid-19 Look Inside 3
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