Corona viruses are a family of viruses that range from the common cold to MERS corona virus: A Review

 

Mr. Mayur S. Jain*, Dr. Shashikant D. Barhate

Shree Sureshadada Jain Institutes of Pharmaceutical Education and Research,

Jammer- 424206, Maharashtra (India).

 

ABSTRACT:

A corona virus is a kind of common virus that causes an infection in your nose, sinuses, or upper throat. Most corona viruses aren't dangerous. COVID-19 is a disease that can cause what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs). It's caused by a corona virus named SARS-CoV-2. It spreads the same way other corona viruses do, mainly through person-to-person contact. Infections range from mild to serious. SARS-CoV-2 is one of seven types of corona virus, including the ones that cause severe diseases like Middle East respiratory syndrome (MERS) and sudden acute respiratory syndrome (SARS). The other corona viruses cause most of the colds that affect us during the year but aren’t a serious threat for otherwise healthy people. In early 2020, after a December 2019 outbreak in China, the World Health Organization identified SARS-CoV-2 as a new type of corona virus. The outbreak quickly spread around the world. ^{[1], [2]}

 

 

 

INTRODUCTION:

Corona viruses are a group of related viruses that cause diseases in mammals and birds. In humans, corona viruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses include some cases of the common cold (which is caused also by certain other viruses, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS, and COVID-19. Symptoms in other species vary: in chickens, they cause an upper respiratory tract disease, while in cows and pigs they cause diarrhea. There are as yet no vaccines or antiviral drugs to prevent or treat human corona virus infections.

 

Corona viruses constitute the subfamily Orthocoronavirinae, in the family Coronaviridae, order Nidovirales, and realm Riboviria^[1],[2]. They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry. The genome size of corona viruses ranges from approximately 26 to 32 kilobases, one of the largest among RNA viruses. They have characteristic club-shaped spikes that project from their surface, which in electron micrographs create an image reminiscent of the solar corona, from which their name derives.

 

A corona virus is a kind of common virus that causes an infection in your nose, sinuses, or upper throat. Most corona viruses aren't dangerous. COVID-19 is a disease that can cause what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs). It's caused by a corona virus named SARS-CoV-2. It spreads the same way other corona viruses do, mainly through person-to-person contact. Infections range from mild to serious. SARS-CoV-2 is one of seven types of corona virus, including the ones that cause severe diseases like Middle East respiratory syndrome (MERS) and sudden acute respiratory syndrome (SARS). The other corona viruses cause most of the colds that affect us during the year but aren’t a serious threat for otherwise healthy people. In early 2020, after a December 2019 outbreak in China, the World Health Organization identified SARS-CoV-2 as a new type of corona virus. The outbreak quickly spread around the world.^[1],[3]

 

Is there more than one strain of SARS-CoV-2?

It’s normal for a virus to change, or mutate, as it infects people. A Chinese study of 103 COVID-19 cases suggests the virus that causes it has done just that. They found two strains, which they named L and S. The S type is older, but the L type was more common in early stages of the outbreak. They think one may cause more cases of the disease than the other, but they’re still working on what it all means.

 

How long will the corona virus last?

 

It’s too soon to tell how long the pandemic will continue. It depends on many things, including researchers’ work to learn more about the virus, their search for a treatment, and the public’s efforts to slow the spread.

 

HISTORY:

Corona viruses were first discovered in the 1930s when an acute respiratory infection of domesticated chickens was shown to be caused by infectious bronchitis virus (IBV).

 

Human corona viruses were discovered in the 1960s. They were isolated using two different methods in the United Kingdom and the United States. E.C. Kendall, Malcom Byone, and David Tyrrell working at the Common Cold Unit of the British Medical Research Council in 1960 isolated from a boy a novel common cold virus B814. The virus was not able to be cultivated using standard techniques which had successfully cultivated rhinoviruses, adenoviruses and other known common cold viruses. In 1965, Tyrrell and Byone successfully cultivated the novel virus by serially passing it through organ culture of human embryonic trachea. The new cultivating method was introduced to the lab by Bertil Hoorn. The isolated virus when intranasally inoculated into volunteers caused a cold and was inactivated by ether which indicated it had a lipid envelope. Around the same time, Dorothy Hamre and John Procknow at the University of Chicago isolated a novel cold virus 229E from medical students, which they grew in kidney tissue culture. The novel virus 229E, like the virus strain B814, when inoculated into volunteers caused a cold and was inactivated by ether.

 

Other human corona viruses have since been identified, including SARS-CoV in 2003, HCoV NL63 in 2004, HCoV HKU1 in 2005, MERS-CoV in 2012, and SARS-CoV-2 in 2019. There have also been a large number of animal corona viruses identified since the 1960s.^[3],[4]

 

MICROBIOLOGY:

STRUCTURE:

Corona viruses are large pleomorphic spherical particles with bulbous surface projections. The average diameter of the virus particles is around 120nm (.12μm). The diameter of the envelope is ~80nm (.08μm) and the spikes are ~20nm (.02μm) long. The envelope of the virus in electron micrographs appears as a distinct pair of electron dense shells.

 

The viral envelope consists of a lipid bilayer where the membrane (M), envelope (E) and spike (S) structural proteins are anchored. A subset of corona viruses (specifically the members of betacorona virus subgroup A) also have a shorter spike-like surface protein called hemagglutinin esterase.

 

Cross-sectional model of a corona virus:

 

GENOME:

Corona viruses contain a positive-sense, single-stranded RNA genome. The genome size for corona viruses ranges from 26.4 to 31.7 kilobases. The genome size is one of the largest among RNA viruses. The genome has a 5′ methylated cap and a 3′ polyadenylated tail.^[3],[4]

 

The genome organization for a corona virus is 5′-leader-UTR-replicase/transcriptase-spike (S)-envelope (E)-membrane (M)-nucleocapsid (N)-3′UTR-poly (A) tail. The open reading frames 1a and 1b, which occupy the first two-thirds of the genome, encode the replicase/transcriptase polyprotein. The replicase/transcriptase polyprotein self cleaves to form nonstructural proteins.

 

Schematic representation of the genome organization and functional domains of S protein for SARS-CoV and MERS-CoV

 

 

REPLICATION CYCLE:

ENTRY:

Infection begins when the viral spike (S) glycoprotein attaches to its complementary host cell receptor. After attachment, a protease of the host cell cleaves and activates the receptor-attached spike protein. Depending on the host cell protease available, cleavage and activation allows the virus to enter the host cell by endocytosis or direct fusion of the viral envelop with the host membrane.

 

On entry into the host cell, the virus particle is uncoated, and its genome enters the cell cytoplasm. The corona virus RNA genome has a 5′ methylated cap and a 3′ polyadenylated tail, which allows the RNA to attach to the host cell's ribosome for translation. The host ribosome translates the initial overlapping open reading frame of the virus genome and forms a long polyprotein. The polyprotein has its own proteases which cleave the polyprotein into multiple nonstructural proteins.^[5],[6]

 

REPLICATION:

A number of the nonstructural proteins coalesce to form a multi-protein replicase-transcriptase complex (RTC). The main replicase-transcriptase protein is the RNA-dependent RNA polymerase (RdRp). It is directly involved in the replication and transcription of RNA from an RNA strand. The other nonstructural proteins in the complex assist in the replication and transcription process. The exoribonuclease nonstructural protein, for instance, provides extra fidelity to replication by providing a proofreading function which the RNA-dependent RNA polymerase lacks.

 

One of the main functions of the complex is to replicate the viral genome. RdRp directly mediates the synthesis of negative-sense genomic RNA from the positive-sense genomic RNA. This is followed by the replication of positive-sense genomic RNA from the negative-sense genomic RNA.^[41] The other important function of the complex is to transcribe the viral genome. RdRp directly mediates the synthesis of negative-sense subgenomic RNA molecules from the positive-sense genomic RNA. This is followed by the transcription of these negative-sense subgenomic RNA molecules to their corresponding positive-sense mRNAs

 

RELEASE:

The replicated positive-sense genomic RNA becomes the genome of the progeny viruses. The mRNAs are gene transcripts of the last third of the virus genome after the initial overlapping reading frame. These mRNAs are translated by the host's ribosomes into the structural proteins and a number of accessory proteins. RNA translation occurs inside the endoplasmic reticulum. The viral structural proteins S, E, and M move along the secretory pathway into the Golgi intermediate compartment. There, the M proteins direct most protein-protein interactions required for assembly of viruses following its binding to the nucleocapsid. Progeny viruses are then released from the host cell by exocytosis through secretory vesicles.

 

TRANSMISSION:

The interaction of the corona virus spike protein with its complement host cell receptor is central in determining the tissue tropism, infectivity, and species range of the virus. The SARS corona virus, for example, infects human cells by attaching to the angiotensin-converting enzyme 2 (ACE2) receptor. ^{[5], [6]}

 

CLASSIFICATION:

Corona viruses (and toroviruses) are classified together on the basis of the crown or halo-like appearance of the envelope glycoproteins, and on characteristic features of chemistry and replication. Most human corona viruses fall into one of two serotypes: OC43-like and 229E-like. These differ in both antigenic determinants and culturing requirements: 229E-like corona viruses can usually be isolated in human embryonic fibroblast cultures; OC43-like viruses can be isolated, or adapted to growth, in suckling mouse brain. There is little antigenic cross-reaction between these two types. They cause independent epidemics of indistinguishable disease.

 

 

The life cycle of a corona virus

 

ORIGIN:

Many human corona virus have their origin in bats. The human corona virus NL63 shared a common ancestor with a bat corona virus (ARCoV.2) between 1190–1449 CE. The human corona virus 229E shared a common ancestor with bat corona virus (GhanaGrp1 Bt CoV) between 1686–1800 CE. More recently, alpaca corona virus and human corona virus 229E diverged sometime before 1960. MERS-CoV emerged in humans from bats through the intermediate host of camels. MERS-CoV, although related to several bat corona virus species, appears to have diverged from these several centuries ago. The most closely related bat corona virus and SARS-CoV diverged in 1986.^[62] A possible path of evolution, of SARS corona virus and keen bat corona viruses, suggests that SARS related corona viruses coevolved in bats for a long time. The ancestors of SARS-CoV first infected leaf-nose bats of the genus Hipposideridae; subsequently, they spread to horseshoe bats in the species Rhinolophidae, and then to civets, and finally to humans ^{[6], [7]}

 

Origins of human corona viruses with possible intermediate hosts

SYMPTOMS OF COVID-19:

Early symptoms include:

·       Fever

·       Dry cough

·       Fatigue

 

The virus can lead to pneumonia, respiratory failure, septic shock, and death. Many COVID-19 complications may be caused by a condition known as cytokine release syndrome or a cytokine storm. This is when an infection triggers your immune system to flood your bloodstream with inflammatory proteins called cytokines. They can kill tissue and damage your organs.

 

If you notice the following severe symptoms in yourself or a loved one, get medical help right away:

·       Trouble breathing or shortness of breath

·       Ongoing chest pain or pressure

·       New confusion

·       Can’t wake up fully

·       Bluish lips or face

 

If you’re infected, symptoms can show up in as few as 2 days or as many as 14. It varies from person to person.

 

According to researchers in China, these were the most common symptoms among people who had COVID-19:

·       Fever 83%-99%

·       Cough 59%-82%

·       Fatigue 44%-70%

·       Lack of appetite 40%-84%

·       Shortness of breath 31%-40%

·       Mucus/phlegm 28%-33%

·       Body aches 11%-35%

 

Some people who are hospitalized for COVID-19 have also have dangerous blood clots, including in their legs, lungs, and arteries. ^{[6], [8]}

 

What to do if you think you have it:

If you live in or have traveled to an area where COVID-19 is spreading:

·       If you don’t feel well, stay home. Even if you have mild symptoms like a headache and runny nose, stay in until you’re better. This lets doctors focus on people who are more seriously ill and protects health care workers and people you might meet along the way. You might hear this called self-quarantine.

·       Call the doctor if you have a fever, cough, and trouble breathing. You need to get medical help as soon as possible. Calling ahead (rather than showing up) will let the doctor direct you to the proper place, which may not be your doctor’s office. If you don’t have a regular doctor, call your local board of health. They can tell you where to go for testing and treatment.

·       Follow your doctor’s advice and keep up with the news on COVID-19. Between your doctor and health care authorities, you’ll get the care you need and information on how to prevent the virus from spreading.

 

COLD VS. FLU VS.

Symptoms	Cold	Flu
Fever	Rare	High (100-102 F), Can last 3-4 days
Headache	Rare	Intense
General aches, pains	Slight	Usual, often severe
Fatigue, weakness	Mild	Intense, can last up to 2-3 weeks
Extreme exhaustion	Never	Usual (starts early)
Stuffy/runny nose	Common	Sometimes
Sneezing	Usual	Sometimes
Sore throat	Common	Common
Cough	Mild to moderate	Common, can become severe
Shortness of breath	Rare	Rare

 

ALLERGIES VS. COVID-19

Symptoms	Allergies	COVID-19 (can range from moderate to severe)
Fever	Never	Common
Headache	Uncommon	Can be present
General aches, pains	Never	Can be present
Fatigue, weakness	Sometimes	Can be present
Extreme exhaustion	Never	Can be present
Stuffy/runny nose	Common	Has been reported
Sneezing	Usual	Has been reported
Sore throat	Sometimes	Has been reported
Cough	Sometimes	Common
Shortness of breath	Rare, except for those with allergic asthma	In more serious infections

 

CAUSES OF THE NEW CORONA VIRUS:

Researchers aren’t sure what caused it. There’s more than one corona virus. They’re common in people and in animals including bats, camels, cats, and cattle. SARS-CoV-2, the virus that causes COVID-19, is similar to MERS and SARS. They all came from bats. Many people who got the disease early on were linked to a large live seafood and animal market in China - you might hear it called a “wet market.” The first cases may have come from animals sold in the market, then spread from person to person.^[6],[8]

 

CORONA VIRUS RISK FACTORS:

Anyone can get COVID-19, and most infections are usually mild, especially in children and young adults. But if you aren’t in an area where COVID-19 is spreading, haven’t traveled from an area where it’s spreading, and haven’t been in contact with someone who has it, your risk of infection is low.

 

People over 65 are most likely to get a serious illness, as are those who live in nursing homes or long-term care facilities, who have weakened immune systems, or who have medical conditions including:

·       Moderate to severe asthma

·       Heart, lung, or liver disease

·       Kidney disease that needs dialysis

·       Severe obesity

·       Diabetes

 

HOW DOES THE CORONA VIRUS SPREAD?

SARS-CoV-2, the virus, mainly spreads from person to person.

 

Most of the time, it spreads when a sick person coughs or sneezes. They can spray droplets as far as 6 feet away. If you breathe them in or swallow them, the virus can get into your body. Some people who have the virus don't have symptoms, but they can still spread the virus.

 

You can also get the virus from touching a surface or object the virus is on, then touching your mouth, nose, or possibly your eyes. Most viruses can live for several hours on a surface that they land on. A study shows that SARS-CoV-2 can last for several hours on various types of surfaces:

·       Copper: 4 hours

·       Cardboard: up to 24 hours

·       Plastic or stainless steel: 2 to 3 days

 

That’s why it’s important to disinfect surfaces to get rid of the virus.

 

CAN CORONA VIRUS BE TRANSMITTED THROUGH GROCERIES, PACKAGES, OR FOOD?

You’re much more likely to get COVID-19 from another person than from packages, groceries, or food. If you’re in a high-risk group, stay home and use a delivery service or have a friend shop for you. Have them leave the items outside your front door, if you can. If you do your own shopping, try to stay at least 6 feet away from other shoppers. That isn’t always possible, so wear a cloth face mask, too.

 

Wash your hands for at least 20 seconds before and after bringing things into your home. The corona virus can linger on hard surfaces, so clean and disinfect countertops and anything else your bags have touched. You can wipe down plastic, metal, or glass packaging with soap and water if you want.

 

There’s no evidence that anyone has gotten COVID-19 from food or food containers. ^{[8], [9]}

 

CORONA VIRUS DIAGNOSIS:

Call your doctor or local health department if you think you’ve been exposed and have symptoms like:

·       Fever of 100 F or higher

·       Cough

·       Trouble breathing

 

In most states, decisions about who gets tested for COVID-19 are made at the state or local level.

 

A swab test looks for signs of the virus in your upper respiratory tract. The person giving the test puts a swab up your nose to get a sample from the back of your nose and throat. That sample goes to a lab that looks for viral material. If it’s there, the test is positive. A negative test could mean there is no virus or there wasn’t enough to measure. That can happen early in an infection. It usually takes 24 hours to get results, but the tests must be collected, stored, shipped to a lab, and processed.

 

The FDA is working with laboratories nationwide to develop more tests.

 

The agency is also granting emergency use authorizations to let doctors use tests it has yet to approve. These include tests that check your blood for things called antibodies. Your immune system makes antibodies in response to an infection.

 

A swab test can only tell whether you have the virus in your body at that moment. But an antibody test can show whether you’ve ever been exposed to the virus, even if you didn’t have symptoms. This is important in officials’ efforts to learn how widespread COVID-19 is. In time, it might also help them figure out who’s immune to the virus.

 

There’s no home test kit for COVID-19. The FDA is cracking down on these bogus products.

 

CORONA VIRUS PREVENTION:

Take these steps:

·       Wash your hands often with soap and water or clean them with an alcohol-based sanitizer. This kills viruses on your hands.

·       Practice social distancing. Because you can have and spread the virus without knowing it, you should stay home as much as possible. If you do have to go out, stay at least 6 feet away from others.

·       Cover your nose and mouth in public. If you have COVID-19, you can spread it even if you don’t feel sick. Wear a cloth face covering to protect others. This isn’t a replacement for social distancing. You still need to keep a 6-foot distance between yourself and those around you. Don’t use a face mask meant for health care workers. And don’t put a face covering on anyone who is:

·       Under 2 years old

·       Having trouble breathing

·       Unconscious or can’t remove the mask on their own for other reasons

·       Don’t touch your face. Corona viruses can live on surfaces you touch for several hours. If they get on your hands and you touch your eyes, nose, or mouth, they can get into your body.

·       Clean and disinfect. You can clean first with soap and water, but disinfect surfaces you touch often, like tables, doorknobs, light switches, toilets, faucets, and sinks. Use a mix of household bleach and water (1/3 cup bleach per gallon of water, or 4 teaspoons bleach per quart of water) or a household cleaner that’s approved to treat SARS-CoV-2. You can check the Environmental Protection Agency (EPA) website to see if yours made the list. Wear gloves when you clean and throw them away when you’re done. ^{[8], [9]}

 

COVID-19 preparation tips:

In addition to practicing the prevention tips listed above, you can:

·       Meet as a household or larger family to talk about who needs what.

·       If you have people at a higher risk, ask their doctor what to do.

·       Talk to your neighbors about emergency planning. Join your neighborhood chat group or website to stay in touch.

·       Find community aid organizations that can help with health care, food delivery, and other supplies.

·       Make an emergency contact list. Include family, friends, neighbors, carpool drivers, doctors, teachers, employers, and the local health department.

·       Choose a room (or rooms) where you can keep someone who’s sick or who’s been exposed separate from the rest of you.

·       Talk to your child’s school about keeping up with assignments.

·       Set yourself up to work from home if your office is closed.

·       Reach out friends or family if you live alone. Make plans for them to check on you by phone or email.

 

CORONA VIRUS TREATMENT:

There’s no specific treatment for COVID-19. People who get a mild case need care to ease their symptoms, like rest, fluids, and fever control. Take over-the-counter medicine for a sore throat, body aches, and fever. But don't give aspirin to children or teens younger than 19. You might have heard that you shouldn't take ibuprofen to treat COVID-19 symptoms -- the World Health Organization made that statement in March 2020. But they reversed it soon after and said there's no proof that taking it causes any harm.

 

Antibiotics won’t help because they treat bacteria, not viruses. If you hear about people with COVID-19 getting antibiotics, it’s for an infection that came along with the disease.

 

People with severe symptoms need to be cared for in the hospital.

 

Many clinical trials are under way to explore treatments used for other conditions that could fight COVID-19 and to develop new ones.

 

Several studies are focused on an antiviral medication called remdesivir, which was created to fight Ebola.

 

An emergency FDA ruling lets doctors use hydroxychloroquine and chloroquine for people hospitalized with COVID-19 and in clinical trials to study them further. The medications are approved to treat malaria and autoimmune conditions like rheumatoid arthritis and lupus.

 

Clinical trials are also under way for tocilizumab, another medication used to treat autoimmune conditions. And the FDA is also allowing clinical trials and hospital use of blood plasma from people who’ve had COVID-19 and recovered to help others build immunity. You’ll hear this called convalescent plasma.^[9],[10]

 

CONCLUSION:

A corona virus is a kind of common virus that causes an infection in your nose, sinuses, or upper throat. Most corona viruses aren't dangerous. COVID-19 is a disease that can cause what doctors call a respiratory tract infection. It can affect your upper respiratory tract (sinuses, nose, and throat) or lower respiratory tract (windpipe and lungs). It's caused by a corona virus named SARS-CoV-2. It spreads the same way other corona viruses do, mainly through person-to-person contact. Infections range from mild to serious. SARS-CoV-2 is one of seven types of corona virus, including the ones that cause severe diseases like Middle East respiratory syndrome (MERS) and sudden acute respiratory syndrome (SARS).

 

ACKNOWLEDGEMENT:

The authors would like to thanks Shree. Sureshadada Jain Institutes of Pharmaceutical Education and Research, Jamner Maharashtra (India) for supporting the fulfillment of this work.

 

CONFLICT OF INTEREST:

Declared none

 

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8.     Myint S, Johnstone S, Sanderson G, Simpson H. An evaluation of ‘nested’ RT-PCR methods for the detection of human corona viruses 229E and OC43 in clinical specimens. Mol Cell Probes. 1994;8: 357–364. [PMC free article] [PubMed].

9.     Sanchez CM, Jimenez G, Laviada MD. et al. Antigenic homology among corona viruses related to transmissible gastroenteritis virus. Virology. 1990; 174:410. [PMC free article] [PubMed].

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Accepted on 12.06.2020      ©Asian Pharma Press All Right Reserved