• Question: How does Corona Virus spread soo fast

    Asked by anon-253206 on 6 May 2020. This question was also asked by anon-253475, anon-253662, anon-256951.
    • Photo: Nicole Wheeler

      Nicole Wheeler answered on 6 May 2020:


      Before the Covid-19 pandemic, 40 million flights, carrying almost 5 billion people were predicted to operate globally in 2020! This number is growing year upon year, meaning that if a new infectious strain of a disease emerges, it can spread locally and internationally at a speed and scale not seen in the past.

      On top of this, coronavirus appears to be contagious before people show symptoms, meaning that even if people are very careful about staying isolated when they’re sick, the infection will still pass between people who appear to be well.

      Every infectious disease has what we call an R0 (r-nought), which is the average number of people that one person with the virus will infect. This number is influenced by human behaviour, how many virus particles need to reach a host to cause infection, how the virus interacts with our immune systems, how well it binds to our cells, and many other things.

      The R0 of the virus, combined with the ability to cause infections before a host shows symptoms has helped this virus spread, but lots of other cold and flu viruses also spread quickly across the world. It’s the severity of the symptoms in some infected people that has drawn everybody’s attention to this virus in particular.

    • Photo: Laura Durrant

      Laura Durrant answered on 7 May 2020:


      Great question! It’s most likely due to crowded conditions and hygiene standards. This is why social distancing and hand washing regulations were put in place – and they seem to be working so far! In terms of the biology of the virus, it has been discovered that some people can catch the virus and not show any symptoms. Without sufficient testing, this makes it difficult to identify everyone who may be positive for the virus. This is why it is important to follow the government guidelines even if we don’t feel unwell.
      I hope this answers your question 🙂 Here’s a link to a website with what some useful info about public health, how viruses spread and the status of COVID-19 vaccinations.
      https://coronavirusexplained.ukri.org/en/

    • Photo: Sandra Greive

      Sandra Greive answered on 11 May 2020:


      This is a fantastic question. SARS-CoV2 (as the virus is called) spreads so rapidly for several reasons. It replicates extremely well in humans, meaning that a single person can make millions of new virus particles. This coronavirus (compared with previous outbreaks of SARS and MERS) has evolved new characteristics that allow it to easily infect human cells so that each individual virus has a really good chance to infect new cells. Many people can be infected but don’t develop disease (called COVID-19), feel ill or show any symptoms. Until we have widespread testing for the virus genome and for antibodies that we make to protect us against the virus, it is hard to tell for sure how many people are affected this way. So far the evidence suggests that these silent infections occur in a significant portion of the people who get infected. Asymtomatic (without symptoms) people can still make many millions of virus particles and because they don’t feel sick, will continue with normal life – travelling, working etc, all the while potentially spreading virus particles through the tiny tiny droplets that can be aerosolised and passed out into the air by coughing and sneezing and less efficiently during normal speech and breathing. Additionally studies have shown that the virus can still be detected (and is likely to be infectious) for up to three days on different surfaces (like door handles and taps etc). This is why good hygiene, such as washing hands thoroughly, covering coughs and sneezes, routine cleaning and physical distancing is so important for all of us to practice even if we don’t feel sick. This significantly reduces the spread of the virus and eventually, because it needs a host survive, it will hopefully die out. We can all play our part!

    • Photo: Hugo Lewkowicz

      Hugo Lewkowicz answered on 11 May 2020:


      Actually, confusingly it’s the fact that it’s slow that has meant that it has spread so fast! A person who gets it might well take over a week to develop symptoms, if they develop symptoms at all. In that time they may have met loads of people and spread it on. If people got sicker quicker we may have been able to get a better handle on it as they could have quarantined themselves earlier, but with loads of people with no symptoms walking around it was able to spread fast.

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