Virus Rules of Engagement
Viruses are biological entities that can only thrive and multiply in a host, which is a living organism such as a plant, an animal or a human. The first virus, identified in 1892, was the Tobacco Mosaic Virus. A few million different viruses have been discovered since then, although only a few thousand have been fully characterised.
All viruses have common behaviours, characteristics and common strategies they employ when interacting with their hosts. They have particular ways or methods of infecting their hosts, akin to “rules of engagement” which determine when, where, how they go about wrecking havoc in their targets.
Viruses are not living organisms
Viruses aren’t actually alive — they don’t grow or move themselves, or eat or use energy, and they can’t reproduce on their own.
Viruses have Diversity
There is more diversity among viruses than among all groups of living organisms combined. New viruses are constantly being described. It would be nearly impossible to describe all of the groups of viruses and their characteristics. They do, however, share certain characteristics such as their basic structure and general replicative cycle. This diversity extends to different modes of transmission and different ways that viruses invade and take over a cell.
Not all viruses cause disease
Yes, viruses are mostly known for their aggressive and infectious nature against their hosts and the diseases they cause, from a mild cold to the serious conditions like severe acute respiratory syndrome (SARS) and HIV. But they’re not all bad. Some viruses can actually kill bacteria, while others can fight against more dangerous viruses. Just as we have good bacteria in our gut such as probiotics which are protective, we also have several protective viruses in our body. Bacteriophages are viruses that infect and destroy specific bacteria. They’re found in the mucus membrane lining in the digestive, respiratory and reproductive tracts.
Viruses are hijackers
Once inside another cell, viruses become hijackers, using the cells’ machinery to produce more viruses. All viruses must gain entry into target cells and usurp the host cellular machinery to propagate and to produce progeny viruses.
Infection MO: Get in, multiply, release, repeat
Though the details of virus infection and replication vary greatly with host type, all viruses share 6 basic steps in their replication cycles. These are: 1) attachment; 2) penetration; 3) uncoating; 4) replication; 5) assembly; 6)release. A virus enters the cell and, using different mechanisms, takes over the cellular protein synthesis machinery to generate the proteins it needs for itself to reproduce. Once all of the necessary parts have been replicated, individual virus particles are assembled and released. Release often takes place in a destructive manner, bursting and killing the host cell. “Like an unwanted guest who eats everything in the refrigerator, uses every clean towel in the house, and on leaving reduces your house to a pile of rubble”.
Some can jump from one species to another
Every animal species hosts unique viruses. Over time some of these have jumped to humans. These are known as zoonotic viruses. In many parts of the world, bush meat and some exotic animals are a source of protein. But the contact with these animals while capturing, cleaning and preparing them for food exposes humans to blood and other bodily fluids that transmit any number of different viruses to humans. Bats are known to harbour exotic viruses that don’t kill the bats but can be transmitted to humans or other animals. We see these market situations in Asia and we have seen this in Africa with Ebola virus. The 1918/19 H1N1 flu likely “jumped” from birds to people (or via pigs), while the much less virulent 2009 H1N1 strain clearly originated in pigs to cause the first human pandemic of the 21st century.
Virus transmission
Viral diseases are transmitted from person to person by direct or indirect contact. Indirect contact infections spread when an infected person sneezes or coughs, sending infectious droplets into the air. If healthy people inhale the infectious droplets, or if the contaminated droplets land directly in their eyes, nose or mouth, they risk becoming ill. This is how coronavirus virus spreads. As does SARS, MERS, the common cold and the flu viruses.
Some viruses may spread through direct contact with a person that has the virus. The human papillomavirus (HPV) can spread via direct contact with the skin. The Epstein-Barr virus, which causes mononucleosis (mono), can spread through saliva, such as while kissing. HIV passes from one person to another through bodily fluids (from sex or sharing needles, syringes). Noroviruses are one type of virus involved in foodborne infections. Insects such as mosquitoes carry the virus that causes Zika from one person to another.
Viruses often change over time
All viruses mutate. When a virus replicates it doesn’t always manage to produce an exact copy of itself. Copying errors and genetic changes naturally occur. This means that, over time, the virus may start to differ slightly in terms of its genetic sequence. Most mutations are harmless and do not affect the properties of the virus. However, some mutations give the virus a selective advantage. Significant changes can make a virus more transmissible as has been the case with the variants of SARS-CoV-2. They may also help the virus evade the immune system or existing treatments.
Viruses are very stable. There is no evidence that a virus can mutate itself away
While the Coronavirus, SARS-CoV-2 is changing genetically over time, experts consider it a relatively stable virus. This is the reason why we have to place our hope on vaccinations. There is no chance it will miraculously disappear. There is no evidence that a virus can mutate itself away. We have no reason to think that will happen. Nothing in our past history suggests it will suddenly disappear and die off. We have lived with many viruses for hundreds of years.
During a pandemic a virus will spread in peaks and troughs of infection
The influenza virus has caused more than 10 pandemics in the last 150 years. In all instances there is a wave that lasts several months then it seems to disappear. After a few months it comes back with a second wave and it tends to be much more severe each time it comes back. This was the case with the 1918 flu pandemic and the 2009 H1N1pandemic. The same thing happens even with less severe pandemics. Viruses continue to transmit until a large part of the population is infected.
Viruses are hard to treat
Viruses are not susceptible to antibiotics. The discovery of antibiotics for treating bacterial infections revolutionized medicine. Antibiotics are the reason we can survive infections that people frequently died from in the past. No “miracle” drugs have been discovered for the treatment of viruses. Drugs exist that can block the replication of certain viruses, for example, but to date, no truly effective virus killing drugs exist. In most instances, treatment of viral infections involves prevention (vaccines) or helping the body to help itself through the restorative powers of sleep, drinking plenty of fluids, taking supplements and consuming vast quantities of chicken soup.
Viruses will continue to be with us
Ebola, Zika, SARS, MERS each took the world by surprise. New viruses and virus strains are constantly emerging. It’s predicted that a more lethal and catastrophic influenza virus will affect the world in the future. Coronaviruses are going to keep being a huge challenge. We have to learn how to live with SARS-CoV-2 virus, but it doesn’t have to overtake us.
