Coronavirus overview

# Overview
Coronavirus is a genus of animal virus belonging to the family Coronaviridae. Coronavirus, named due to the "crown" like appearance of its surface projections, was first isolated from chickens in 1937. In 1965, Tyrrell and Bynoe used cultures of human ciliated embryonal trachea to propagate the first human coronavirus (HCoV) in vitro. There are now approximately 15 species in this family, which infect not only humans but cattle, pigs, rodents, cats, dogs and birds (some are serious veterinary pathogens, especially chickens). Coronavirus gained international popularity after the deadly SARS epidemic caused by SARS-CoV in 2002 - 2003. A novel coronavirus known as the MERS-CoV was the highlight of the year 2012 when it caused the Middle East respiratory syndrome (MERS) epidemic. 2019 Novel Coronavirus (2019-nCoV) is a virus identified as the cause of an outbreak of respiratory illness first detected in Wuhan, China. Based on the grouping, coronavirus can be classified into three groups. It can also be classified into families based on the genome and the method of replication. The virus can also be classified based on human infectivity. Coronavirus infection is very common and occurs worldwide. The incidence of infection is strongly seasonal, with the greatest incidence in children in winter. Adult infections are less common. The number of coronavirus serotypes and the extent of antigenic variation is unknown. Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak. Due to the lack of data, the exact incidence rate of coronavirus infections can not be approximated. With 8,098 confirmed cases, the case fatality-rate of SARS was 9.6%. With 2465 laboratory-confirmed cases, the case fatality-rate of MERS was 34.4%. The case fatality-rate of 2019-nCoV in the first 99 patients at a Wuhan hospital (the epicenter of the outbreak) has been found to be 11%. Diagnosis of coronaviruses causing infection in humans is based on combination of clinical and epidemiological criteria. Close contact with infected individuals, travel to endemic area and detection of viral RNA in the patient's serum are the most important criteria for confirmation of diagnosis. The history of coronavirus infection includes exposure to an infected animal or human. Patients report flu like symptoms in the initial stages. Infected people can also report upper respiratory symptoms. Common symptoms of coronavirus infection include fever, cough, and shortness of breath. The incubation period can vary depending on the infection. The mean incubation period for 2019-nCoV has been set to be 5.2 days. The pathognomonic physical examination findings in patients infected with coronavirus include fever, flu-like-symptoms, cough, and body aches. General appearance of the patient infected with coronavirus depends on the incubation period of the illness. The chest x ray findings in a suspected case of coronavirus infection can mimic the findings in pneumonia. There are no specific ECG findings associated with coronavirus infection. Non specific findings can include sinus tachycardia and diffuse T wave inversion. Chest CT scan findings in patients infected with coronavirus can include unilateral or bilateral pneumonia, mottling and ground glass opacity, focal or multifocal opacities, consolidation, and septal thickening with subpleural and lower lobe involvement more likely. Treatment should be supportive. No specific treatment available. Most people with coronavirus illness will recover on their own.

# Historical Perspective
Coronaviruses were first isolated from chickens in 1937. In 1965, Tyrrell and Bynoe used cultures of human ciliated embryonal trachea to propagate the first human coronavirus (HCoV) in vitro. There are now approximately 15 species in this family, which infect not only man but cattle, pigs, rodents, cats, dogs and birds (some are serious veterinary pathogens, especially chickens). Coronavirus gained international popularity after the deadly SARS epidemic caused by SARS-CoV in 2002 - 2003. A novel coronavirus known as the MERS-CoV was the highlight of the year 2012 when it caused the Middle East respiratory syndrome (MERS) epidemic. 2019 Novel Coronavirus (2019-nCoV) is a virus identified as the cause of an outbreak of respiratory illness first detected in Wuhan, China.

# Classification
Based on the grouping, coronavirus can be classified into three groups. It can also be classified into families based on the genome and the method of replication. The virus can also be classified based on human infectivity.

# Epidemiology and Demographics
Coronaviruses have a worldwide distribution, causing 10-15% of common cold cases. Infections show a seasonal pattern with most cases occurring in the winter months. Coronavirus infection is very common and occurs worldwide. The incidence of infection is strongly seasonal, with the greatest incidence in children in winter. Adult infections are less common. The number of coronavirus serotypes and the extent of antigenic variation is unknown. Re-infections appear to occur throughout life, implying multiple serotypes (at least four are known) and/or antigenic variation, hence the prospects for immunization appear bleak. Due to the lack of data, the exact incidence rate of coronavirus infections can not be approximated. With 8,098 confirmed cases, the case fatality-rate of SARS was 9.6%. With 2465 laboratory-confirmed cases, the case fatality-rate of MERS was 34.4%. The case fatality-rate of 2019-nCoV in the first 99 patients at a Wuhan hospital (the epicenter of the outbreak) has been found to be 11%.

# Risk Factors
The most significant risk factor for coronavirus infection is exposure. to infected animals or humans.

# Screening
There is insufficient evidence to recommend routine screening for coronavirus infection.

# Natural History, Complications and Prognosis
Coronavirus infection can have a highly variable disease course. The infection can range from being subclinical to being an overt clinical condition. Coronavirus infection is most commonly complicated by respiratory distress indicating mechanical ventilation and ICU care. The prognosis of the coronovirus infection is highly dependent on the type of the virus involved and the disease presentation. It has been noted that young children, elderly, immunocompromised, and individuals with comorbid conditions are at the highest risk for worse prognosis.

# Diagnosis

## Diagnostic criteria
Diagnosis of coronaviruses causing infection in humans is based on combination of clinical and epidemiological criteria. Close contact with infected individuals, travel to endemic area and detection of viral RNA in the patient's serum are the most important criteria for confirmation of diagnosis.

## History and Symptoms
The history of coronavirus infection includes exposure to an infected animal or human. Patients report flu like symptoms in the initial stages. Infected people can also report upper respiratory symptoms. Common symptoms of coronavirus infection include fever, cough, and shortness of breath. The incubation period can vary depending on the infection. The mean incubation period for 2019-nCoV has been set to be 5.2 days.

## Physical Examination
The pathognomonic physical examination findings in patients infected with coronavirus include fever, flu-like-symptoms, cough, and body aches. General appearance of the patient infected with coronavirus depends on the incubation period of the illness.

## Laboratory Findings
Laboratory tests can be done to confirm whether illness may be caused by human coronaviruses. However, these tests are not used very often because people usually have mild illness. Also, testing may be limited to a few specialized laboratories. Laboratory tests include serology for viral antigen, molecular testing and viral culture. All these tests can be used to confirm infection with coronavirus.

## Chest X-Ray
The chest x ray findings in a suspected case of coronavirus infection can mimic the findings in pneumonia.

## Electrocardiogram
There are no specific ECG findings associated with coronavirus infection. Non specific findings can include sinus tachycardia and diffuse T wave inversion.

## Echocardiography and Ultrasound
There are no specific echocardiography/ultrasound findings associated with coronavirus infection. Non specific echocardiographic findings can include left ventricular systolic dysfunction and pericardial effusion.

## CT Scan
Chest CT scan findings in patients infected with coronavirus can include unilateral or bilateral pneumonia, mottling and ground glass opacity, focal or multifocal opacities, consolidation, and septal thickening with subpleural and lower lobe involvement more likely.

## MRI
There are no specific MRI findings associated with coronavirus infection. MRI can aide in making the diagnosis on the basis of exclusion.

## Other Diagnostic Studies
Research laboratories have used isolation methods, electron microscopy, serology and PCR-based assays to diagnose coronavirus infections for surveillance studies.

# Treatment

## Medical Therapy
Treatment should be supportive. No specific treatment available. Most people with coronavirus illness will recover on their own.