Coronavirus: Introduction, mode of transmission, symptoms, treatment and prevention

coronavirus

Introduction

Coronavirus is a group of spherical or pleomorphic medium sized (100-150 nm), enveloped RNA virus, containing pectal or club shaped peplomers on the surface as shown above picture. Their name  coronavirus  is due to crown shape, corona meaning crown. These viruses belong to family Coronaviridiae and there are four genera Alphacoronavirus, Betacoronavirus, Gammacoronavirus and Deltacoronavirus. These viruses infect mammals and birds causing diseases of the respiratory tract , gastrointestinal tract, liver, kidneys and nervous system while there are seven strains of human coronaviruses:

  1. Human coronavirus 229E (HCoV-229E)
  2. Human coronavirus OC43 (HCoV-OC43)
  3. SARS-CoV
  4. Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus)
  5. Human coronavirus HKU1
  6. Middle East respiratory syndrome coronavirus (MERS-CoV), previously known as novel coronavirus 2012 and HCoV-EMC.
  7. Novel coronavirus (2019-nCoV) also known as Wuhan pneumonia or Wuhan coronavirus.(‘Novel’ in this case means newly discovered, or newly originated, and is a placeholder name.) Note -The coronaviruses HCoV-229E, -NL63, -OC43, and -HKU1 continually circulate in the human population and cause respiratory infections in adults and children world-wide but  not important as other resting strains like SARS-CoV, MERS-CoV and 2019-nCoV.

Severe Acute Respiratory Syndrome (SARS)

In November 2002, South China had an outbreak of an unusual respiratory infection, with many deaths. In February 2003, a physician from China  visited Hong Kong , fell ill and died after infecting twelve people. Theses twelve people went to their countries to fall ill and also initiated outbreaks there. In February in Hanoi , Vietnam, an unusual case of pneumonia was reported by a hospital which sought the help of  a WHO office in this connection. Dr. Carlo Urbani , the WHO infectious disease specialist advised for the quarantine but by then outbreaks had involved many countries including USA, Canada, Ireland, Hong Kong, China, Taiwan, some European countries  and many countries in South East Asia . This new disease was  named ‘Severe Acute Respiratory Syndrome'(SARS). It  affected over 30 countries, with many thousand cases and about 800 deaths. India escaped the SARS outbreak. Dr. Carlo Urbani , who identified this new epidemic participated in its control and died of the disease. A coronavirus was found in the repiratory secrections of these patients by electron microscopy and conformed by growth in Vero cell culture , cloning , sequencing and animal inoculation. This coronavurus appeared to be a new virus different from other coronaviruses and this strain is SARS-CoV.

Middle East respiratory syndrome

In September 2012, a new type of coronavirus was identified, initially called Novel Coronavirus 2012, and now officially named Middle East respiratory syndrome coronavirus (MERS-CoV).The World Health Organization issued a global alert soon after.The WHO update on 28 September 2012 stated that the virus did not seem to pass easily from person to person.However, on 12 May 2013, a case of human-to-human transmission in France was confirmed by the French Ministry of Social Affairs and Health. In addition, cases of human-to-human transmission have been reported by the Ministry of Health in Tunisia. Two confirmed cases involved people who seemed to have caught the disease from their late father, who became ill after a visit to Qatar and Saudi Arabia. Despite this, it appears that the virus has trouble spreading from human to human, as most individuals who are infected do not transmit the virus. By 30 October 2013, there were 124 cases and 52 deaths in Saudi Arabia. After the Dutch Erasmus Medical Centre sequenced the virus, the virus was given a new name, Human Coronavirus–Erasmus Medical Centre (HCoV-EMC). The final name for the virus is Middle East respiratory syndrome coronavirus (MERS-CoV). In May 2014, the only two United States cases of MERS-CoV infection were recorded, both occurring in healthcare workers who worked in Saudi Arabia and then traveled to the U.S. One was treated in Indiana and one in Florida. Both of these individuals were hospitalized temporarily and then discharged. In May 2015, an outbreak of MERS-CoV occurred in the Republic of Korea, when a man who had traveled to the Middle East, visited 4 different hospitals in the Seoul area to treat his illness. This caused one of the largest outbreaks of MERS-CoV outside of the Middle East. As of December 2019, 2,468 cases of MERS-CoV infection had been confirmed by laboratory tests, 851 of which were fatal, a mortality rate of approximately 34.5%.

Novel coronavirus (2019-nCoV)

In December 2019, a pneumonia outbreak was reported in Wuhan, China. On 31 December 2019, the outbreak was traced to a novel strain of coronavirus,which was labeled as 2019-nCoV by the World Health Organization (WHO)According to Daniel Lucey at Georgetown University, the first human infections must have occurred in November 2019 or earlier.As of 30 January 2020, there have been 214 confirmed deaths and more than 8,230 confirmed cases in the coronavirus pneumonia outbreak.The Wuhan strain has been identified as a new strain of Betacoronavirus from group 2B with an ~70% genetic similarity to the SARS-CoV.The virus was suspected to have originated in snakes, but many leading researchers disagree with this conclusion.Daniel Lucey, an infectious disease specialist at Georgetown University, stated that “Now it seems clear that the seafood market is not the only origin of the virus”. Now in details about Novel coronavirus (2019-nCoV).

Mode of transmission

Coughs or sneezes from infected person or touching contaminated objects.

Symptoms of Novel coronavirus (2019-nCoV)

Symptoms are divided into common and severe symptoms.

Common symptoms includes-

  1. Fever
  2. after 2 to 7 days , develop a dry cough
  3. Mild breathing difficulties at the outset
  4. Gastrointestinal issues
  5. Diarrhoea
  6. General body aches

while severe symptoms includes-

  • High fever ( 100.4°F or higher)
  • Pneumonia
  • Kidney failure
  • Death

Laboratory Diagnosis 

  1. Polymerase Chain Reaction (PCR): Reverse transcriptase PCR (RT-PCR) has been used for early diagnosis.
  2. Isolation of virus: Nasopharyngeal washings are used for the isolation of virus. Human coronaviruses can be cultured in human foetal tracheal organ culture. Some strains may grow on momolayers of diploid human embryonic fibrolasts, with minimal cytopathic effects.
  3. Demonstration of antigen: Coronavirus antigens can be detected in respiratory secretions by ELISA test.
  4. Antibody detection: The rise in titres of antibodies in paired serum samples can be demonstrated by the ELISA  or indirect immunofluorescent test.

Treatment and prophylaxis

There is lacking proper antiviral drugs and vaccine and therefore, no specific treatment or prophylaxis is available . The virus is highly mutable, hence vaccine may not be easy to prepare however preparation in trial. In this period, strict isolation and quarantine are the only ways to control the disease.

Prevention

Novel coronavirus has just been declared a public health emergency of international concern by the World Health Organization (WHO). Here are few ways to protect yourself, your childen and your community:

  1. Wash your hands frequently using alcohol-based sanitizer or soap and water.
  2. When coughing and sneezing , cover your mouth and nose with your flexed elbow or a tissue -then throw away the tissue immediately and wash your hands.
  3. Avoid close contact with anyone who has a fever and cough .
  4. Seek medical care early if you have a fever , cough and difficulty breathing, and tell your doctor about your travel history.
  5. If you visit  a live market in an area with reported cases of coronavirus , avoid direct unprotected contact with live animals and surfaces they have touched.
  6. Don’t consume raw or under -cooked animal products. Handle raw meat , milk or animal organs with care to avoid cross -contamination with uncooked foods.
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