Virus Spreading

Virus Spreading

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NIAID Rocky Mountain Laboratories (RML), U.S. NIH , CC BY-SA

What is a virus? How do they spread? How do they make us sick?

Published: March 13, 2020 3.42am GMT

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Molecular biology

Coronavirus

Viruses

COVID-19

Associate Professor, Genomics and Molecular Biology; Biomedical Sciences., Bond University

Associate Professor Lotti Tajouri is affiliated with Dubai Police Scientist Council.
Bond University provides funding as a member of The Conversation AU.
Viruses are the most common biological entities on Earth. Experts estimate there are around 10,000,000,000,000,000,000,000,000,000,000 of them, and if they were all lined up they would stretch from one side of the galaxy to the other .
You can think of them as nature’s own nanotechnology: molecular machines with sizes on the nanometre scale, equipped to invade the cells of other organisms and hijack them to reproduce themselves. While the great majority are harmless to humans, some can make you sick and some can even be deadly.
Viruses rely on the cells of other organisms to survive and reproduce, because they can’t capture or store energy themselves. In other words they cannot function outside a host organism, which is why they are often regarded as non-living .
Outside a cell, a virus wraps itself up into an independent particle called a virion. The virion can “survive” in the environment for a certain period of time, which means it remains structurally intact and is capable of infecting a suitable organism if one comes into contact.
When a virion attaches to a suitable host cell – this depends on the protein molecules on the surfaces of the virion and the cell – it is able to penetrate the cell. Once inside, the virus “hacks” the cell to produce more virions. The virions make their way out of the cell, usually destroying it in the process, and then head off to infect more cells.
Does this “life cycle” make viruses alive? It’s a philosophical question, but we can agree that either way they can have a huge impact on living things.
At the core of a virus particle is the genome, the long molecule made of DNA or RNA that contains the genetic instructions for reproducing the virus. This is wrapped up in a coat made of protein molecules called a capsid, which protects the genetic material.
Some viruses also have an outer envelope made of lipids, which are fatty organic molecules. The coronavirus that causes COVID-19 is one of these these “enveloped” viruses. Soap can dissolve this fatty envelope, leading to the destruction of the whole virus particle. That’s one reason washing your hands with soap is so effective!
Viruses are like predators with a specific prey they can recognise and attack. Viruses that do not recognise our cells will be harmless, and some others will infect us but will have no consequences for our health.
Many animal and plant species have their own viruses. Cats have the feline immunodeficiency virus or FIV, a cat version of HIV, which causes AIDS in humans. Bats host many different kinds of coronavirus, one of which is believed to be the source of the novel coronavirus that causes COVID-19.
Bacteria also have unique viruses called bacteriophages, which in some cases can be used to fight bacterial infections .
Viruses can mutate and combine with one another. Sometimes, as in the case of COVID-19, that means they can switch species.
The most important ones to humans are the ones that infect us. Some families of viruses, such as herpes viruses, can stay dormant in the body for long periods of time without causing negative effects.
How much harm a virus or other pathogen can do is often described as its virulence. This depends not only on how much harm it does to an infected person, but also on how well the virus can avoid the body’s defences, replicate itself and spread to other carriers.
In evolutionary terms, there is often a trade-off for a virus between replicating and doing harm to the host. A virus that replicates like crazy and kills its host very quickly may not have an opportunity to spread to a new host. On the other hand, a virus that replicates slowly and causes little harm may have plenty of time to spread.
Once a person is infected with a virus, their body becomes a reservoir of virus particles which can be released in bodily fluids – such as by coughing and sneezing – or by shedding skin or in some cases even touching surfaces.
The virus particles may then either end up on a new potential host or an inanimate object. These contaminated objects are known as fomites, and can play an important role in the spread of disease.
The coronavirus COVID-19 is a member of the virus family coronaviridae , or coronaviruses. The name comes from the appearance of the virus particles under a microscope: tiny protein protrusions on their surfaces mean they appear surrounded by a halo-like corona.
Other coronaviruses were responsible for deadly outbreaks of Serious Acute Respiratory Syndrome (SARS) in China in 2003 and Middle East Respiratory Syndrome (MERS) from 2012. These viruses mutate relatively often in ways that allow them to be transmitted to humans.
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People with flu can spread it to others up to about 6 feet away. Most experts think that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.
People with flu are most contagious in the first three to four days after their illness begins. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Children and some people with weakened immune systems may pass the virus for longer than 7 days.
Symptoms can begin about 2 days (but can range from 1 to 4 days) after the virus enters the body. That means that you may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Some people can be infected with a flu virus but have no symptoms. During this time, those people may still spread the virus to others.
You may be able to pass on flu to someone else before you know you are sick, as well as while you are sick.
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SCIENTISTS are creating “super-infectious” viruses that could have “irreversible consequences” for the planet, experts have warned.
The “risky virology” sees scientists tweak viruses in labs to make them spread easily between hosts, in the hope of developing viral vaccines, according to a new paper penned by top academics at King’s College London.
These scientists create super-infections which are “self-spreading” so that they can be released into the environment or exposed to a population.
The idea is the virus can be used to protect a population quickly and will spread on its own - vaccinating humans or protecting crops.
However, experts now warn that this approach goes against the long-established view that such viruses are too unstable to be safe.
Dr Filippa Lentzos, from the Department of War Studies and the Department of Global Health & Social Medicine, has called it “risky virology”.
She said: “Developing self-spreading viruses for environmental release is another example of risky virology research, like virus hunting in bat caves or deliberately making dangerous pathogens even more dangerous in the lab, all in the name of pandemic preparedness, but where it is far from clear that the anticipated benefits outweigh the very clear risks.”
The authors of the paper are now calling for greater regulation and discussion of the risks and benefits of such viruses.
They said: “Only a concerted, global governance effort with coherent regional, national and local implementation can tackle the challenges of self-spreading viruses that have the potential to radically transform both wildlife and human communities."
It is not the first time scientists have looked at the concept of self-spreading viruses.
In the 1980s in Australia in the 1980s a research programme was looking at using them to sterilise or kill pests.
And in the 1990s in Spain a similar approach was considered to protect native wild rabbits.
However, both were abandoned over warnings that the potential consequences were too serious.
In 2016 interest reignited in the idea, and currently the European Union, the US National Institutes of Health and the US Defense Advanced Research Projects Agency are funding proposals around using such viruses for wildlife immunisations.
It comes as the origins of the devastating Covid pandemic remain a mystery as China refuses to cooperate with a full-scale probe into the source of the deadly virus.
And evidence of a lab leak has been piling up over the last year as scientists, researchers and governments hunt for answers.
Dozens of scientists have suggested Covid could have escaped from the Wuhan Institute of Virology in China through an infected researcher, improper disposal of waste, or potential breaches in the security at the site.
The high security facility specalising in coronaviruses has been in the eye of the storm as questions rage over whether Covid could have escaped from its lab.
One bombshell book said the virus appeared to have been "tailor made for carnage" and may have escaped from the lab after a scientist was bitten by an infected monkey.
Both China and the lab have furiously denied any allegations, but top former intelligence bosses said the evidence of a lab "accident" is clear to see - and there has been a calculated cover up "from day one".
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There's another deadly virus brewing in the Northeastern United States.
Those words may be hard to hear, but there's some good news as well: you're extremely unlikely to catch it.
The eastern equine encephalitis (EEE) virus can cause a severe brain infection, and it can be transmitted through a mosquito bite, as OneZero reports .
As the virus' name suggests, horses are particularly susceptible to infection. There's a vaccine for horses — but no specific treatment plan or approved human vaccine.
Luckily, transmission and infection are both extremely rare. Since it was first discovered in humans in 1938, there have been less than 100 cases in the US, according to OneZero .
In 2019, for instance, there were only 38 human cases recorded and 15 deaths in the US, according to the US Centers for Disease Control and Prevention. About 95 percent of those bitten by EEE-carrying mosquitoes never end up developing an infection.
Those numbers couldn't be more different from the current coronavirus pandemic. The United States alone crossed the two million cases threshold this week, with over 1,000 people dying from COVID-19 related deaths every 24 hours.
But once infected, the EEE virus is deadly. Mortality rate is about 33 percent , according to the National Environmental Health Association. Those who survive will have to battle with sometimes crippling neurological impairments.
Scientists are also worried that with rising temperatures caused by global warming, the number of outbreaks of the virus appear to be on the rise — in large part due to growing mosquito populations during prolonged summer periods, according to OneZero .
At the end of the day, despite the risks, it's important not to take the EEE virus too far out of context.
"We try our best to make people aware of the risks without sensationalizing," Catherine Brown, state epidemiologist at the Massachusetts Department of Public Health, told OneZero . "But there are still people who are so fearful of EEE that they kind of forget that there are other things going on in the world."

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