Taipei European School
A non-living infectious agent that typically consists of a nucleic acid molecule (DNA or RNA) in a (fatty) protein coat. It is too small to be seen by a normal microscope. It is able to multiply only when it is in a living cell of a host (meaning that it does not replicate on food like bacteria do).
For a full description of how viruses work try: https://www.livescience.com/53272-what-is-a-virus.html
Or a video
For COVID-19 facts and tips try:
BBC Horizon programme on current research
Important thing to notice is that viruses are really small and much smaller than bacteria. They ‘infect’ all life forms, both plants and animals, and have been around for a very, very long time. Humanity took a long time to discover them because they could not be seen under an optical microscope. We can visualise them now by ‘looking’ at them using an electron microscope.
They cannot be treated by antibiotics (which attack microscopic living organisms). We can only treat the symptoms like reducing temperature when we are attacked. We can protect against them by vaccinating which trains the body to stop them spreading. The Smallpox virus was eradicated in 1980 by a worldwide vaccination programme. If viruses are stopped from spreading then they will disappear. This happened with the SARS virus but sadly it is clear that we were not able to manage this for the COVID-19 virus. The virus has been called Sars-Cov-2, COVID-19 is the disease (COrona VIrus Disease 2019).
They are generally specialists in attacking cells in one species. Unfortunately humans, pigs and birds are all susceptible to similar flu viruses and it is easily possible for a virus to change slightly during the replication process (mutation) and they can cross species. Recently a tiger in the New York zoo was infected. Some groups of people are saying that it isn’t natural for humans and animals to be living so closely together and so more viruses are likely to cross species and be problematic.
This crossing of species only happens when they are in close contact for long periods of time. The theory about the COVID-19 virus is that it came from bats because it has so many similarities with bat viruses but then the move to humans is still being debated because bats are not normally in contact with humans so they think that there is an animal linking bats to humans. Currently the thought is Pangolins but there is no firm evidence for that.
COVID-19 is a respiratory tract infection (airways and lungs) that spreads mainly through coughs, sneezes and talking. Between 20,000 and 40,000 particles are given out in a sneeze, less for a cough or talking but certainly enough to pass on the virus. This is why social distancing is really important. At more than 1.5 m away you are unlikely to be infected. Surfaces are only infected if someone gets fluid from inside the airways onto that surface, that is why not sneezing, coughing or talking without mouth and nose covering is important. A mask doesn’t offer much protection from receiving the virus (it can access the body through the eyes) but is a major protection if the virus carrier wears one. To protect the eyes normal glasses or goggles help but in hospital they will wear a full face visor. Remember virus carriers do not always have symptoms. The virus is not spread through the digestive tract (unlike Norovirus) and does not come out in sweat and so it is only particles that come from the nose and mouth.
The corona virus ‘particles’ break down when they are not in cells but can survive in water droplets for a long time. When the water evaporates or is removed they quickly break down leaving traces of DNA or RNA (COVID-19 is and RNA type). There was a story in the press about the virus being found on one of the cruise ships 17 days after it had been cleaned. It was not virus particles that were found but the RNA evidence that it had been there. It was not infectious.
A virus remains active for different periods of time depending on the surface and the virus ‘coat’. COVID-19 virus appears to last about 6 hours as droplets in the air (keep air moving indoors), 24 hours on cardboard, 2 to 3 days on steel and plastic (clean frequently used surfaces). The route of infection from a surface is droplets from a carrier deposited on the surface, someone else touches the surface with the hand. The hand goes to the face (eyes, nose or mouth) and then the virus gets into the system, attacks cells and multiplies. Frequent hand cleansing, keeping hands away from the face or wearing a mask to stop you touching your face will all help.
There is a general trend for flu and cold viruses to be seasonal with colds being more common in October, November and December and flu viruses in January, February and March. Not enough research has been done in this area but suppositions about people being outdoors more in summer and the environmental changes (temperature, humidity and UV penetration from the sun). These are some of the things that may cause differences:- High humidity could help the virus be viable for longer (less evaporation). UV light also breaks down many chemicals, industrial UV cleaning would require quite large doses of high energy UV-C which fortunately does not get through our atmosphere because it would also destroy our skin. UV-B affects skin and probably has an effect on the virus but we don’t know how big an effect and UV-A (the lowest energy UV) will have a lesser impact. Temperature could affect the chemical breakdown, generally higher temperature causes faster changes. A lot more research needs to be done in this area and will probably now get funding because of this outbreak.
The number of cases and deaths shown in the news, or more reputably by Johns Hopkins University, Baltimore (https://coronavirus.jhu.edu/map.html) are really quite poor indicators of what is really happening. Many deaths are not reported as COVID-19 deaths and reported cases are mainly indications of how many suspected cases have been tested. Some countries have not done many tests because the suspects were not ill enough and there was a shortage of tests. Some countries have deliberately underreported in order to keep the country working. Any figures have to be questioned. (but I still look at them!)
Source: Modified for Scarlett Middle School from NPR by Christopher Thomas. Original work: A comic for Kids exploring the New Coronavirus by NPR (English), There is also a Simplified Chinese edition.