What you need to know about viruses
GP and mother of three
It is hard to open a newspaper or switch on the radio at the moment without being exposed to increasingly concerning updates about the coronavirus outbreak. This World Health Organisation-declared global health emergency had infected almost 10,000 people by last Friday, and killed more than 200, and is spreading far more quickly than Sars (severe acute respiratory syndrome) did in the early 2000s.
There are heaps of unknowns about the novel coronavirus, including exactly where it originated, but each day that passes will no doubt bring new information that should ultimately lead to a better understanding as to how we can stop the spread and treat those infected.
As alarming as this outbreak is, what we do have on our side is a wealth of information about viruses in general, collated over many decades, and this can inform our approach to this outbreak:
■ The name virus comes from Latin and means ‘‘poison’’.
■ The first virus identified that could infect humans was the yellow fever virus, and was discovered by a man named Walter Reed in 1901.
■ Viruses are very unusual entities, being neither truly alive, nor dead, and are not actually classified as a living organism. This is because they cannot survive on their own – they need a host organism to reproduce. Depending on the type of virus, effective hosts can be plants, animals, fungi, birds or humans. Viruses are the most abundant biological entity on the planet.
■ Viruses are tiny – so small that they cannot be detected with a normal microscope, and you could fit tens of millions of viruses on to the head of a pin. An average virus is 20-300 nanometres in diameter, compared with an E coli bacteria that is about
1000nm across.
■ They are basic structures, made up of some nucleic acid (genetic material) that can be DNA or RNA depending on the virus type, housed in a protective shell made of protein called the capsid. The capsids of varying virus types have very different shapes, allowing them to be easily differentiated by scientists. Some viruses also have a membrane outside the capsid called the envelope.
■ The coronavirus is an RNA-virus and has an envelope. Its name comes from the Latin word for crown, as its particles have a characteristic shape reminiscent of a royal crown.
■ When viruses infect their host (whether a plant, animal, bird or human), they effectively hijack their cells, become activated and start to reproduce, invading more cells as they go. This is the process that makes the host unwell.
■ Bacteria differ from viruses in that they can survive on their own and do not need a host to activate them. They can also be effectively inactivated, or even killed, by antibiotics which sadly have absolutely no effect on viruses.
Viruses can cause a huge range of diseases – from well-known ones such as measles, the common cold and influenza, to rarer ones that you are likely to never encounter (think monkeypox or Kyasanur Forest disease).
The symptoms caused by the infection will depend on the type of virus involved. Some viruses, such as Ebola, lead to infections that have huge mortality rates, while others will trigger an illness that is barely noticeable to its host.
Viruses can also have one effect on one type of host but a very different one on another (for example, some viruses can be lethal to cats but hardly cause any symptoms for a dog even though they may still use it as a host).
A virus’s only purpose is to reproduce. Once it has achieved that in a host, the offspring of the original virus can invade new cells and new hosts – this is how viral infections spread to cause outbreaks. There are many ways viruses can spread but the exact mechanism will depend on the type of virus: some viruses can be transmitted from mother to unborn child, others are spread through infected faeces or blood, touch, or via sexual contact.
Other types will require a ‘‘transmitter’’ or vector to enable them to spread, usually insects as is the case with dengue fever.
Coronaviruses are actually a group of viruses, rather than just the ‘‘novel-type’’ (named
2019-nCoV) that is causing the current outbreak. In humans, coronaviruses typically cause respiratory infections (so illnesses affecting the lungs or airways, including our nasal passages, throats, sinuses and ears), and most of the time these are mild – the virus that causes your average winter cold is a type of coronavirus.
However, some coronaviruses, such as the novel-type we are seeing today and the Sars virus from 18 years ago, can be far more dangerous. Some coronaviruses can also affect chickens, leading to respiratory issues, and cows and pigs, where they can lead to diarrhoea.
The newly identified novel coronavirus seems able to spread from human to human, which is not the case for all viruses – it is possible that it has mutated or changed its form, as viruses tend to do, to enable this to happen.
At this stage, we do not fully understand everything about this virus but it appears to be spread by infected droplets, for example when breathing, sneezing or coughing. It is also possible
that you could be exposed to the virus by touching an object that has an infected droplet on it – we know that some viruses, such as the flu virus, can remain active and potentially infectious for days on inanimate objects or surfaces such as furniture or books, and it is likely that 2019-nCoV has the same capability.
As viruses are not inactivated by antibiotics, treatment options are limited. Some drugs, known as antivirals, have been developed that can halt or slow down the reproduction cycle of the virus, and these are widely used to treat diseases like HIV and hepatitis.
At this stage there is no antiviral agent known to be effective against the novel coronavirus, though testing is happening around the world to try to identify one that will have some impact.
The most effective way to manage virus outbreaks is vaccination.
Vaccination programmes have had enormous impacts on morbidity and mortality around the world (the recent measles outbreak in Samoa being a stark example of what can happen when rates of immunisation drop below a certain threshold). It is likely a vaccine can be developed that will protect people from infection with coronavirus but there is none in existence at present. Based on how long it takes to develop and ensure the efficacy and safety of a new vaccine, we are likely looking at 12 months minimum before one could be widely available.
Until vaccination is available, there are some simple things we can do to reduce the likelihood of spread, should cases appear in New Zealand. The most important is to recognise potential symptoms and isolate anyone thought to be carrying the virus – this is crucial but recent reports indicate coronavirus can potentially spread in the 10 days or so before any symptoms appear, so this will make effective ‘‘quarantine’’ difficult to achieve.
For all of us, maintaining really good hygiene, particularly when it comes to hand washing is important, and this applies to limiting the spread of any infection, not just coronavirus.
Focusing on our general health and resilience is important too – the fitter and stronger we are, the more able we will be to fight off a virus.
So ensuring our bodies get good nutrition, plenty of vitamins, enough sleep, and minimising the ‘‘baddies’’ including alcohol and smoking, is at this stage the best way to keep ourselves well.
The virus that causes your average winter cold is a type of coronavirus.