What is a coronavirus?
According to the World Health Organization (WHO), coronaviruses are a family of viruses that cause illnesses ranging from the common cold to more severe diseases such as severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS).
These viruses were originally transmitted from animals to people. SARS, for instance, transmitted from civet cats to humans while MERS moved to humans from a type of camel. Several known coronaviruses are circulating in animals that have not yet infected humans. The name coronavirus comes from the Latin word corona, meaning crown or halo. Under an electron microscope, the virus looks like it is surrounded by a solar corona.
The novel coronavirus, identified by Chinese authorities on January 7 and since named SARS-CoV-2, is a new strain that had not been previously identified in humans. On 11 February 2020, the World Health Organization (WHO) announced a new name for the epidemic disease caused by 2019-nCoV: coronavirus disease (COVID-19). Regarding the virus itself, the International Committee on Taxonomy of Viruses has renamed the previously provisionally named 2019-nCoV as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2.
Coronavirus disease 2019 (COVID-19)
It is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was first identified in December 2019 in Wuhan, the capital of China’s Hubei province, and has since spread globally, resulting in the ongoing 2019–20 coronavirus pandemic. Based on the evidence of a rapidly increasing incidence of infections and the possibility of transmission by asymptomatic carriers, SARS-CoV-2 can be transmitted effectively among humans and exhibits high potential for a pandemic.
Coronaviruses are naturally hosted by bats and it is believed that most human coronaviruses are derived from the bat reservoir. Genomic sequence studies of COVID-19 have identified nearly 50%, 79% and 96% similarity to MERS-CoV, SARS-CoV-1, and bat SARS-related coronavirus, respectively. The specific route of transmission to humans from natural reservoirs is still yet to be known, however, some of the studies suggest pangolin could be the intermediate mammalian hosts. Since the spike protein of SAR-CoV-2 is nearly identical to one virus isolated from pangolin, it is believed that pangolins could have provided a partial spike gene to SARS-CoV-2, to infect mammals. A recent study has also shown the development of new variations at the functional sites in the receptor-binding domain of the spike of SARS-CoV-2 and viruses from pangolin, likely caused due to either a natural selection or mutations or recombination or both. Nevertheless, once a human is infected, the virus could also be transmitted from human-to-human through the respiratory droplets and aerosols from coughing and sneezing, like other respiratory pathogens, including SARS-CoV. SARS-CoV-2 also uses the angiotensin-converting enzyme II (ACE2) receptors like the SARS-CoV. The incubation period of COVID-19 could vary from 3 days to 14 days.
Signs and symptoms of COVID-19 may appear two to 14 days after exposure and can include:
- Shortness of breath or difficulty breathing
Other symptoms can include:
- Runny nose
- Sore throat
Some people have experienced the loss of smell or taste.
The severity of COVID-19 symptoms can range from very mild to severe. Some people may have no symptoms at all. People who are older or who have existing chronic medical conditions, such as heart disease, lung disease or diabetes, or who have compromised immune systems may be at higher risk of serious illness. This is similar to what is seen with other respiratory illnesses, such as influenza.
Depending on the clinical features of COVID-19, patients are generally divided as mild, moderate, severe and critical.
Mild COVID-19: low-grade fever, cough, malaise, rhinorrhea, sore throat with or without hemoptysis, nausea, vomiting, diarrhea, but without any radiological features of pneumonia and absence of mental changes.
Moderate COVID-19: fever, respiratory symptoms including dry cough and shortness of breath that may emerge along with the radiological features.
Severe COVID-19: dyspnea, respiratory frequency ≥30/minute, blood oxygen saturation ≤93%, PaO2/FiO2 ratio <300, and/or lung infiltrates >50% of the lung field within 24-48 hours.
Critical COVID-19: usually develops after 7 days in patients with mild/ moderate/severe COVID-19 with features of Acute respiratory distress syndrome (ARDS) requiring mechanical ventilation along with the presence of multiorgan dysfunction failure, metabolic acidosis, and coagulation dysfunction. Source: World Health Organization (WHO)
Although most people with COVID-19 have mild to moderate symptoms, the disease can cause severe medical complications and lead to death in some people. Older adults or people with existing chronic medical conditions are at greater risk of becoming seriously ill with COVID-19.
Complications can include:
- Pneumonia in both lungs
- Organ failure in several organs
Global is facing a terrible virus with greater infectivity than the SARS-CoV pandemic of 2003. There is presently no vaccine or documented specific anti-SARS-CoV-2 drug regimen to treat critically ill patients. Most of the potential drugs for the treatment of COVID-19 are being investigated for safety and efficacy against SARS-CoV-2. Remdesivir is the most promising agent. Also, favipiravir and combination therapy with hydroxychloroquine plus azithromycin appear to be acceptable alternatives for the treatment of COVID-19 patients. For patients with SARS-CoV-2 infection, ACE inhibitor and ARB need to be prescribed with caution. Compared with nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen might be a safer agent for treating fever in COVID-19 patients. Finally, low-dose steroids (hydrocortisone) might be prescribed for the treatment of refractory shock in patients with COVID-19.
Hemogram: leukopenia especially lymphopenia (in 80% of cases), mild thrombocytopenia. However, leukocytosis has also been reported. Some researchers suggested neutrophil-to-lymphocyte ratio (NLR) as an independent risk factor for severe illness and NLR ≥ 3.13 was considered as the threshold for progression to severe illness in COVID-19 patients.
Inflammatory Markers: serum procalcitonin is normal initially, may increase with severity. Increase in C-Reactive Protein (CRP), lactate dehydrogenase (LDH), SGOT, troponin, D-dimer, ferritin, Creatine kinase, and ESR. CRP may be used to track the severity of the disease. Severe and critically ill patients may have very high levels of other inflammatory markers, interleukin (IL)-6, IL-4, IL-10, and tumor necrosis factor (TNF)-α. Poor laboratory prognostic factors include high D-Dimer, lymphopenia, thrombocytopenia, CRP.
Serology: Blood sampling is much easier than swab sampling from oropharynx or nasopharynx.
Two kinds of serological test can detect COVID-19 –
Enzyme-linked immune-sorbent assay (ELISA) and
Immuno chromatography (Card test).
RT-PCR and genomic sequencing (wherever available) is the gold standard and confirmatory test for COVID-19.
Recommendations and advice for the public
During previous outbreaks due to other coronaviruses (Middle-East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), human-to-human transmission occurred through droplets, contact, and fomites, suggesting that the transmission mode of the 2019-nCoV can be similar. The basic principles to reduce the general risk of transmission of acute respiratory infections include the following:
- Avoiding close contact with people suffering from acute respiratory infections.
- Frequent hand-washing, especially after direct contact with ill people or their environment.
- Avoiding unprotected contact with farm or wild animals.
- People with symptoms of acute respiratory infection should practice cough etiquette (maintain distance, cover coughs and sneezes with disposable tissues or clothing, and wash hands).
- Within health care facilities, enhance standard infection prevention and control practices in hospitals, especially in emergency departments.