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Novel Coronavirus (COVID-19)
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- A new strain of the coronavirus that has not been identified previously is called a novel coronavirus (nCov).
- Coronavirus disease 2019 is an infectious disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), a virus closely related to the SARS virus.
- The 2019-nCov has been given the official name COVID-19.
- WHO declared COVID-19 infections a public health emergency of international concern and later called it a pandemic.
- Though the novel coronavirus is highly infectious and spreads rapidly, the death rate is low – only about 3.7%.
- However, because of the possibility of a global-scale infection, all possible steps should be taken to prevent the fast spreading of the outbreak. Most people recover from the COVID-19 infection within 28 days, when proper supportive care is given.
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Viruses and Viral Infections
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- Viruses are found everywhere and their origins are unclear.
- Viruses are neither dead nor alive, but to be considered inhabiting ‘the edge of life’.
- They have a simple structure – a genetic material, DNA or RNA, surrounded by a protein called the capsid. Although viruses have genes, they don’t have a cellular structure and hence viruses cannot reproduce without infecting a cell.
- Once inside, they assemble inside the cell, and using the machinery of the host cell they produce copies of themselves.
- Release of the virus from the host cell causes the bursting of its membrane and cell wall, thus killing the cell.
Broadly viruses can be classified as DNA viruses and RNA viruses based on the genetic material within them.
- A DNA virus enters the nucleus of the host cell and using the cell’s enzymes, it’ll replicate the viral DNA.
- An RNA virus will inject the RNA into the cytoplasm (the material inside a living cell excluding the nucleus) to synthesize proteins and form replica viruses. Alternatively the RNA can be converted to DNA using a process called reverse transcription. This DNA will be integrated with that of the host DNA in a process similar to a DNA virus.
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Coronavirus Genome
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- Coronavirus consists of an RNA genome and is one of the largest in the RNA family.
- Coronaviruses are enveloped and contain single-stranded positive-sense RNA. The RNA attaches to the host cell’s ribosome for translation. Positive sense RNA can function as messenger RNA, meaning that viral RNA sequence may be directly translated into the desired viral proteins.
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Coronavirus (COVID-19) – Origin and Transmission
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- Coronaviruses originate in animals like camels and bats and are zoonotic diseases as it passes from animals to humans occasionally.
- The source of a zoonotic disease is called reservoir species. (For SARS, the reservoir species was identified as bats).
- The first known case of COVID-19 was reported in the Chinese city of Wuhan in December 2019 and was traced to an animal market in the city.
- Research is ongoing on how COVID-19 spreads. However, as per WHO, the disease spreads in humans via exposure to respiratory secretions – the small droplets from the nose or mouth of an infected person – either directly or indirectly.
- The basic reproduction number (R_0) is a measure of transmissibility that aims to describe the average number of people a new case will infect. For COVID-19, WHO estimates R_0 = 1.4 to 2.5. However, many researchers think this figure is under-estimated.
- Compared to earlier outbreaks of SARS and MERS, COVID-19 has a greater global spread and researchers think that mutation in the virus strain is enabling it to be more efficiently transmitted.
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Coronavirus (COVID-19) – Clinical Manifestations
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- In humans, it affects the upper respiratory tract with varying severity.
- Respiratory infections range from the common cold to bronchiolitis. Pneumonia, gastroenteritis and neurological disorders can also occur.
- Other symptoms are headache, chills, sore throat, and cough.
- The incubation period is from 2 to 5 days and symptoms have a range of 3 to 18 days.
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Coronavirus (COVID-19) – Prevention and Treatment
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- No vaccine is currently available to prevent COVID-19.
- Avoiding exposure is the only way to prevention. Preventive actions include:
- Avoiding close contact with infected people.
- Avoiding touching eyes, nose, and mouth.
- Staying home when infected and using a facemask.
- Covering while coughing or sneezing.
- Disinfecting frequently touched objects and surfaces.
- No specific antiviral treatment is recommended for COVID-19. Infected people should receive supportive care based on symptoms and for severe cases, treatment should support vital organ functions.
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Other Human Coronaviruses
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Two other human coronaviruses, MERS-CoV and SARS-CoV were previously identified.
- Middle East Respiratory Syndrome (MERS): MERS cases were reported mainly in the Arabian Peninsula. Symptoms usually include fever, cough, and shortness of breath which often progress to pneumonia. About 3 or 4 out of every 10 patients reported with MERS have died.
- Severe acute respiratory syndrome (SARS): It is believed that the 2003 SARS epidemic started when the virus spread from small mammals in China. SARS symptoms often included fever, chills and body aches which usually progressed to severe pneumonia and breathing difficulty. SARS is more deadly but much less infectious than COVID-19. There have been no outbreaks of SARS anywhere in the world since 2003.
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Know the difference: Outbreak, Epidemic, and Pandemic
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- An outbreak is the occurrence of disease cases in excess of what’s normally expected. An epidemic is when there is a sudden increase in reports of a particular disease in a particular area (say a state or country). When an epidemic spreads over several countries or continents it is called a pandemic.
- When Coronavirus was limited to Wuhan, it was an outbreak. It became an epidemic when it spread across China. It is now a pandemic as it spreads worldwide.
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