The Coronavirus and MERS: Viral Infection and Prevention
Coronaviruses and Their Effects
Coronaviruses are interesting and sometimes dangerous viruses that infect humans and other animals. They often make us sick, but the severity of the illness varies. The infection may be deadly, as in the disease caused by the MERS virus, or minor, resulting in symptoms that are no more serious than the common cold.
Viruses can change over time as they gain, lose, or change genes. The genes are responsible for the characteristics of the virus. Every now and then a report appears announcing that a novel variety of coronavirus has been discovered. One type that is currently of concern is the MERS or Middle East Respiratory Syndrome virus. Although this causes mild symptoms in some people, it often produces a serious disease.
Health agencies around the world are tracking the spread of MERS carefully. In this age of frequent international travel, infections can easily spread from country to country. Luckily, there are things that we can do to greatly reduce our chance of catching a virus. There are also ways in which we can boost the activity of our immune system, which protects us from infections.
What Is a Biological Virus?
Viruses are very different from other living things. In fact, some scientists don't consider viruses to be alive. Unlike living organisms, they aren't made of cells. Instead, they consist of a core of nucleic acid (DNA or RNA) surrounded by a coat of protein. The protein coat is known as a capsid. Some viruses, including coronaviruses, have a lipid envelope surrounding their capsid.
Another difference between viruses and cellular organisms is that viruses can't reproduce on their own. They must enter a cell of a living organism in order to make new copies of themselves.
Although a virus has a simpler structure than a cell, it's still impressive. It has the amazing ability to trick the cells that it infects. It not only passes through the protective membrane surrounding a cell but also stimulates it to make virions (viral nucleic acid surrounded by a capsid, or individual virus particles) instead of its own products. The virions then destroy or damage the cell as they enter the outside world.
How Does a Virus Get into Cells?
The "goal" of a virus is to send its nucleic acid into a cell. The nucleic acid contains genes that encode the instructions for making new virions.
Viruses seem to have three ways of accomplishing their goal. Each method requires a virion to bind to receptor proteins on the cell membrane before an infection begins.
- Viruses that infect bacteria (bacteriophages) inject their nucleic acid into a bacterium while leaving their capsid outside.
- The lipid envelope of some viruses fuses with the cell membrane, which is also rich in lipids. The capsid and nucleic acid are then released into the cell.
- Some viruses enter cells by a process called endocytosis. The cell membrane forms an invagination or pocket that engulfs and surrounds a virion. The pocket then separates from the cell membrane, forming a sac with the virion inside. The virion later breaks out of the sac.
A coronavirus enters a cell by both membrane fusion and endocytosis. Researchers are studying the ways in which the virus attaches to the protein receptors of cell membranes and then enters the cells. If scientists can interfere with these processes they should be able to stop an infection.
Types of Endocytosis
Understanding Viral Entry
Viral Reproduction and Exit
Once inside the cell, the nucleic acid of the virus takes over the cell's equipment, causing the cell to make new viral nucleic acid molecules and new protein coats. The virions are then assembled.
The virions may burst out of the cell, destroying it in a process called lysis. In some types of virus, however, the virions are released through the cell membrane in a gentler process. These additional methods still damage the cell, however, and usually kill it.
One "gentler" method by which virions leave cells is called budding. In the budding process, a virion produces a bud-like swelling on the cell membrane. As the bud splits off, a bit of broken cell membrane surrounds the released virus particle. This is the method by which many viruses get their lipid envelope.
Another method of viral release is called exocytosis, which is the opposite process to endocytosis. A vesicle (sac) carrying the virion fuses with the cell membrane and releases its contents to the outside environment. Coronaviruses are released by exocytosis.
Viral entry, reproduction and exit are complex processes. More details of these processes need to be discovered. The benefits obtained from the discoveries could be wonderful, though, since viruses cause diseases in humans, animals and plants. Understanding viral behavior could lead to new treatments for diseases.
Structure of Coronaviruses
A coronavirus is named for its appearance under an electron microscope. The virions are covered by club-shaped projections or spikes made of protein. These reminded early observers of a crown or the rays of the sun's corona. "Corona" is the Latin word for crown.
A coronovirus virion has an irregular shape but is often roughly circular. It contains a single strand of RNA, or ribonucleic acid, which is helical and contains genes. The human body contains RNA too, but our genes are present in DNA, or deoxyribonucleic acid. The genes of other organisms and of many viruses are also present in DNA.
The RNA molecule of a coronavirus virion is large and is surrounded by a protein capsid. This is in turn surrounded by an envelope made of lipid. Protein molecules are present in the lipid envelope and on its surface.
A coronavirus is made of an RNA molecule (green in the diagram above) surrounded by a capsid made of protein (red). A lipid envelope (purple) surrounds the capsid. Protein molecules are present in the envelope and on its surface. The ones on the surface look like spikes.
A Coronavirus Infection
Coronaviruses are transmitted in droplets released from the respiratory system. We release these droplets as we sneeze, cough or speak. It's thought that the viruses are also transmitted though personal contact, such as by shaking hands. In addition, a person may become infected when they touch a contaminated surface.
Coronaviruses cause problems in the upper respiratory tract, but most of them don't produce a serious infection. The usual symptoms resemble those of the common cold and include a runny nose, sneezing, coughing, a sore throat, and a fever. Most people have been infected by a coronavirus at some time. There may be multiple incidences of infection in a person's life. The affected person usually recovers without help.
Coronoviruses may sometimes cause problems in the lower respiratory tract, such as pneumonia, but these problems generally occur in people who have a weakened immune system or in elderly people. In some cases - especially in children - the viruses cause problems in the digestive tract.
Antiviral drugs are available to treat some viral infections, but most can't be cured by drugs. Doctors have to treat the symptoms rather than the infection itself. They can prescribe medications to reduce fever, relieve pain and make breathing easier, for example. Although the body has to destroy the virus on its own, medical support can be very helpful.
While most coronaviruses cause relatively benign infections, some can cause serious symptoms and may be deadly. The SARS virus and the MERS virus are examples. Their full names are SARS-CoV and MERS-CoV, where CoV stands for coronavirus.
The SARS Virus, or SARS-CoV
The SARS coronavirus appeared in 2003. The last case was diagnosed in 2004. Like the MERS virus today, the SARS virus was called a "novel" coronavirus because it was a new variety that had never been observed in humans before. The first symptom of the infection was usually a high fever. This was often followed by a headache and body aches. Serious respiratory problems often developed, including pneumonia. Diarrhea was sometimes present, too. According to the World Health Organization, or WHO, 8,098 people were diagnosed with SARS and a total of 774 people died.
The MERS Virus, or MERS-CoV
The MERS coronavirus, or MERS-CoV, was first observed in 2012 in Saudi Arabia. Researchers know that it's potentially dangerous, but they still have much to learn about the virus.
According to WHO, as of the start of January 2017:
- 1,864 MERS cases had been reported to WHO.
- 659 people deaths from the infection had been reported to the organization.
- The MERS virus had been found in 27 countries.
The death rate from the infection is worrying. Health agencies say that the current risk of infection is low for residents of North America, however. They are aware of the potential for the virus to spread globally and are monitoring the situation closely. They also say that we should follow the recommended procedures for reducing the chance of a viral infection. These procedures are described below.
Trying to Understand MERS
Transmission of Disease
The transmission of the MERS virus is not well understood. It seems to pass from one person to another through close contact. It may be transmitted via camels as well. The virus has been discovered in camels and some people have become sick after handling the animals. ThIs doesn't prove that camels can transmit MERS to humans, though.
WHO recommends that people wash their hands before and after approaching camels and that they avoid animals who are obviously sick. They also recommend that people avoid eating or drinking raw or undercooked camel meat, milk or urine. (Yes, some people do drink camel urine!)
People who visit countries with MERS cases need to make sure that they take steps to avoid infections. The majority of these countries are located in or near the Arabian Peninsula. In 2015 an outbreak occurred in Korea, however. According to the CDC (Centers for Disease Control and Prevention), so far this has been the largest outbreak of the disease outside the peninsula. It originated from a traveller returning to Korea from an infected area. The WHO webpage mentioned in the "References" section below is useful for travellers because it contains the latest news about MERS outbreaks.
Middle East Respiratory Syndrome
Symptoms and Treatment
Like the SARS virus, the MERS virus produces symptoms beyond the respiratory system. In people who get sick from the infection, the patient generally has a fever, shortness of breath and a cough. The respiratory system symptoms may be severe. The patient may also experience diarrhea, nausea and vomiting. Possible complications include pneumonia and kidney problems.
Strangely, some people don't get sick when they're infected by the MERS virus or experience only mild symptoms that resemble those of a cold. According to the CDC, people with pre-existing medical conditions may be more likely to experience severe symptoms or to die from the infection.
At the moment, there is no specific treatment for MERS. Medical care is very important, though. Doctors can support the patient's recovery by relieving symptoms and protecting vital organs.
Preventing Viral Infections
There are a variety of ways in which people can greatly reduce the chance of getting sick from a viral or a bacterial infection and can also reduce the chance of infecting someone else. Here are ten suggestions that are recommended by health agencies.
- Wash hands frequently, especially before eating and after a high-risk event such as using a bathroom.
- Wash hands for at least twenty seconds per session. One common suggestion that may be helpful for children (and perhaps for adults too) is to wash the hands for as long as it takes to sing "Happy birthday to you" twice.
- Use soap and water to wash the hands, but if these aren't available, use an alcohol-based hand sanitizer instead.
- Wash or disinfect objects that are touched frequently, such as door knobs, faucet handles and toilet flushers.
- Flush toilets when the lids are down to avoid contact with the spray that's released and to prevent the germ-laden spray from spreading through the air.
- Consider using a towel with a different colour or pattern for each family member. This will reduce the chance of an infection passing from one person to another.
- Don't touch your mouth, nose or eyes unless you have just washed your hands.
- Avoid close contact with people if they are obviously sick.
- Cover your mouth or nose when you sneeze - but not with your hands, which can transfer the germs to other surfaces when you touch them. Use a tissue. If you don't have one, sneeze into your sleeve and wash the area or clothing as soon as possible.
- Stay home when you're sick.
How many of the ten suggestions do you follow to prevent viral infections?
Maintaining a Healthy Immune System
While it's important to follow steps to reduce the chance of catching a virus, the steps aren't foolproof. Therefore it's a good idea to keep the immune system functioning well. If the immune system is strong, it will be able to destroy many viruses.
A healthy lifestyle boosts immunity. A good diet that emphasizes a wide variety of whole, unprocessed foods and is low in sugar will be a big aid to improving and maintaining immunity. Moderate and regular exercise has been shown to boost the immune system, while smoking weakens it. Getting adequate sleep and taking steps to relieve stress can also help the immune system to function efficiently.
Although following a healthy lifestyle isn't a guarantee that we won't get sick, it can certainly improve the odds. It also increases the chance that any infection that we experience will be mild instead of serious. Since another of its benefits is to reduce the chance of other diseases besides infections, it's a good idea to follow a healthy lifestyle whenever possible.
© 2013 Linda Crampton