Covid-19 is the condition caused by the current coronavirus outbreak; a virus more properly called SARS-CoV-2. A coronavirus is a type of virus that can cause disease in mammals and birds. These are usually mild respiratory tract infections such as the common cold. There are currently no vaccines to prevent human coronavirus infections. They can also cause much rarer conditions such as SARS or Covid-19 which can be lethal.
As of Friday the 21st February 2020 there have been 76,769 confirmed cases of SARS-CoV-2 infection, of which 75,569 have been in China with 2,239 deaths. There are currently 1,200 confirmed cases outside China (spread over 26 countries) with 8 deaths.
Another type of virus is the influenza (flu) virus which causes regular, seasonal outbreaks throughout the world. In a typical year it will infect anywhere from 3 to 5 million people, resulting in between 250,000 and 500,000 deaths. Although that is a very speculative figure – I have heard ‘infectious disease’ doctors saying that they have never heard of anyone dying from the flu. It turns out that some of the published data are estimates and possibly not very good ones at that.
Every year vaccines are produced to protect people against flu. The influenza virus mutates rapidly so every year a new vaccine needs to be produced. The World Health Organisation predicts which of the various strains of flu are most likely to take hold on the population and then the vaccine manufacturers have six months to produce the millions of vaccines required. The vaccine is usually an inactive form of the virus that encourages your immune system to produce antibodies so that if you ever encounter the real virus your body can suppress it before it makes you ill. It normally takes two weeks from having the vaccination until your immunity has built up. It is possible to catch the flu during this period which is why some people claim “the vaccine gave me the flu”.
Viruses are not considered to be alive because they are not able to reproduce outside a host cell. They add their genetic material (usually RNA) into the DNA within the cell and then the host makes copies of the virus. Often this happens with no ill effect to the host but sometimes this is associated with disease.
One of the main ways in which viruses are spread is by touching a surface with your hand and picking up some virus particles then touching your eyes, nose or mouth. That is why thorough washing of your hands is often cited as the best thing we can all do to combat the spread of viral diseases.
Questions…
- What characteristic do birds and mammals share, that other chordates do not?
- What makes up the respiratory tract?
- Why are viruses not considered to be alive?
- Name another groups of disease causing organisms and the group of chemicals that doctors use to combat them.
- [Harder] How does RNA differ from DNA?
Comments