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Abstract
Human coronaviruses, first characterized in the 1960s, are responsible for a substantial proportion of upper respiratory tract infections in children. Since 2003, at least 5 new human coronaviruses
HISTORY
The history of human coronaviruses began in 1965 when Tyrrell and Bynoe1 found that they could passage a virus named B814. It was found in human embryonic tracheal organ cultures obtained from the respiratory tract of an adult with a common cold. The presence of an infectious agent was demonstrated by inoculating the medium from these cultures intranasally in human volunteers; colds were produced in a significant proportion of subjects, but Tyrrell and Bynoe were unable to grow the agent in tissue culture at that time. At about the same time, Hamre and Procknow2 were able to grow a virus with unusual properties in tissue culture from samples obtained from medical students with colds. Both B814 and Hamre's virus, which she called 229E, were ether-sensitive and therefore presumably required a lipid-containing coat for infectivity, but these 2 viruses were not related to any known myxo- or paramyxoviruses. While working in the laboratory of Robert Chanock at the National Institutes of Health, McIntosh et al3 reported the recovery of multiple strains of ether-sensitive agents from the human respiratory tract by using a technique similar to that of Tyrrell and Bynoe. These viruses were termed “OC” to designate that they were grown in organ cultures.
Within the same time frame, Almeida and Tyrrell4 performed electron microscopy on fluids from organ cultures infected with B814 and found particles that resembled the infectious bronchitis virus of chickens. The particles were medium sized (80–150 nm), pleomorphic, membrane-coated, and covered with widely spaced club-shaped surface projections. The 229E agent identified by Hamre and Procknow2 and the previous OC viruses identified by McIntosh et al3 had a similar morphology
In the late 1960s, Tyrrell was leading a group of virologists working with the human strains and a number of animal viruses. These included infectious bronchitis virus, mouse hepatitis virus and transmissible gastroenteritis virus of swine, all of which had been demonstrated to be morphologically the same as seen through electron microscopy.5,6 This new group of viruses was named coronavirus (corona denoting the crown-like appearance of the surface projections) and was later officially accepted as a new genus of viruses.7
CORONAVIRUS GENOME AND STRUCTURE
Coronaviruses are medium-sized RNA viruses with a very characteristic appearance in electron micrographs of negatively stained preparations (Fig. 1). The nucleic acid is about 30 kb long, positive in sense, single stranded and polyadenylated. The RNA is the largest known viral RNA and codes for a large polyprotein. This polyprotein is cleaved by viral-encoded proteases to form the following: an RNA-dependent RNA polymerase and an ATPase helicase; a surface hemagglutinin-esterase protein present on OC43 and several other group II coronaviruses; the large surface glycoprotein (S protein) that forms the petal-shaped surface projections; a small envelope protein (E protein); a membrane glycoprotein (M protein); and a nucleocapsid protein (N protein) that forms a complex with the RNA. The coding functions of several other ORFs are not clear. The strategy of replication of coronaviruses involves a nested set of messenger RNAs with common polyadenylated 3-ends. Only the unique portion of the 5-end is translated.21 Mutations are common in nature. In addition, coronaviruses are capable of genetic recombination if 2 viruses infect the same cell at the same time.
All coronaviruses develop in the cytoplasm of infected cells (Fig. 2), budding into cytoplasmic vesicles from the endoplasmic reticulum. These vesicles are either extruded or released from the cell within the same time frame, and then the cell is destroyed.
All group I coronaviruses, including 229E, use human aminopeptidase N as their cellular receptor.27 Mouse hepatitis virus, a group II coronavirus, uses a member of the carcinoembryonic antigen family as its receptor.28 The receptor for OC43 is not known, but it may be 1 of several cell surface molecules, including 9-O-acetylated neuraminic acid and the HLA-I molecule.29 The SARS coronavirus uses angiotensin-converting enzyme II as its cellular receptor.30,31
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Answer:
An outbreak of the coronavirus (now called COVID-19) in China is causing global concern. It came from a seafood and meat market in Wuhan, China, in December. It has since spread to other countries, including the United States.
Despite Wuhan and other Chinese cities being quarantined, the COVID-19 has spread to almost 70 locations internationally. In the U.S., COVID-19 cases have been confirmed and deaths have been reported.
What is a coronavirus?
A coronavirus is a virus that is found in animals and, rarely, can be transmitted from animals to humans and then spread person to person. In addition to COVID-19, other human coronaviruses have included:
- The MERS virus, or Middle East respiratory syndrome.
- The SARS virus, or severe acute respiratory syndrome, which first occurred in the Guangdong province in southern China.
What are the symptoms of a coronavirus?
COVID-19 symptoms range from mild to severe. It takes 2-14 days after exposure for symptoms to develop. Symptoms may include:
- fever
- cough
- shortness of breath
Those with weakened immune systems may develop more serious symptoms, like pneumonia or bronchitis. You may never develop symptoms after being exposed to COVID-19. So far, most confirmed cases are in adults, but some children have been infected. There is no evidence that children are at greater risk for getting the virus.
What causes a coronavirus infection?
Humans first get a coronavirus from contact with animals. Then, it can spread from human to human. Health officials do not know what animal caused COVID-19.
The COVID-19 virus can be spread through contact with certain bodily fluids, such as droplets in a cough. It might also be caused by touching something an infected person has touched and then touching your hand to your mouth, nose, or eyes.
How is a coronavirus diagnosed?
If you believe you have COVID-19, you should contact your family doctor immediately. Before going to the doctor’s office, call with your concerns. This will allow the office to collect information and offer you guidance on next steps. To diagnose you, your doctor may run tests to rule out other common infections. In some cases, your doctor may suggest you self-isolate to prevent the spread of infection. The FDA has also seen unauthorized fraudulent test kits for COVID-19 being sold online. Currently, the only way to be tested for COVID-19 is to talk to your family doctor.
Can a coronavirus be prevented or avoided?
Practice social distancing. Avoid people who are sick or meeting in large groups. Stay home if you are sick. Cover your cough with a tissue or cough into your upper sleeve or elbow. Do not cough into your hands.
Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom, before eating, and after blowing your nose, coughing, or sneezing. If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol. Always wash hands with soap and water if hands are visibly dirty. Avoid touching your mouth, nose, or eyes.
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