[First circulated 25th February 2020]
What is the virus?
CoVid 19 is one of the family of viruses, the corona virus, that causes the common cold and is not, for example, part of the influenza virus group
How is it spread?
It seems that it is mainly spread from person to person and not via droplets hanging around in the air. Although it can be spread direct into your nose, the hands can be a major source of infection: ie if you touch your face after your hands have had contact with the virus from an infected person
How infectious is it?
Experts probably don’t know exactly. There are two meanings of “how infectious”?
- How many individuals can one person infect? On average this appears to be quite small and a figure of 2-3 people get the infection from any one other affected person seems to be the major conclusion. But this is obviously influenced by how much contact such an individual has. The idea of a ‘super infectious person’ is probably a myth
- If you are not immune and you are sufficiently exposed to the virus, how likely is it you will get the infection? Again, this is not clear, but seemingly the risk is very high as few people will be naturally immune and the virus is quite effective
Are people infectious before they know they have the virus?
This appears to be the big problem and say differs from other corona viruses-if you have a cold you are only infectious when you have symptoms and are shedding the virus. CoVid-19 has a particular property of fooling the body’s first line of immune defence when it enters the nasal airway. The body’s first line defence is thus not activated and the virus multiplies and sheds. So, for around 3 days after contracting the virus, the infected individual, who will be feeling fine, will be shedding virus into the air to those who are in close contact
Are masks effective at preventing spread (should I wear one?)
Masks are now ubiquitous in China and other countries in South East Asia. Obviously, carers and close family members of affected people should wear masks. There is now a world shortage of effective masks (most are made in China). Indeed, the NHS is worried that there may not be enough for its own workers should a major epidemic take hold. Experts say for low risk countries, such as the UK, it is unnecessary for normal healthy people to wear a mask to prevent them getting infected All websites emphasise the importance of proper hand washing (with soap and water) and not touching the face especially when having been in contact with a person with symptoms.
What are the consequences of getting an infection?
As the newspapers and other media report, the mortality rate is around 2% which is similar to that for normal seasonal flu. Indeed, it might be lower than 2% as many mild cases are not reported. But what about the other 98%. For most, the symptoms will be like a mild cold and chest infection. But, the problem is that the virus, not stopped by the body’s fist line of defence, then penetrates deep into the lungs and can cause pneumonia and other chest infections. This virus particularly likes the cells that line the lungs and sticks to them. The data from China suggest that perhaps 1 in 7 will have significant pneumonia. Again, most such people will recover from a viral pneumonia. There are a few people who then mount an exaggerated immune response to the infection in their lungs and then there is a massive battle between the virus and the immune response which can be very serious and probably explains the young deaths reported
Are any people specifically at risk of having a bad time?
As you might expect, elderly people, especially those over 80, with pre-existing lung disease and who have weakened immune systems are more likely to have complications and not be able to mount a good if delayed immune response. But what about ‘normal healthy people? The short answer is that the experts do not know why most previously healthy people have a mild disease while others can get a significant pneumonia. Interestingly, men seem to have worse disease (twice as likely to get complications – but this has been seen in other epidemics in the past eg SARS and MERS). There may be a genetic risk, but what these are is not known
Why don’t some of the existing anti-viral drugs work?
Sadly, the drugs that were tested for treating other influenza outbreaks such as Relenza (Zanamivir)and Tamiflu (Oseltamivir) are not likely to be effective against CoVid 19. Indeed, despite government’s stockpiling millions of doses following the 2004 outbreak, the clinical trial evidence was even very weak for that and related epidemic.
An Israeli company has started an urgent clinical trial to see if they have an effective drug for the small number of people with acute severe pneumonia, but that is based on stopping the fight between the immune system and the virus and would not be used for ordinary infection
Why can’t they get a vaccine quickly?
There is now a vaccine in trial against MERs, a related corona virus, which does seem to be safe and effective but will need to be tested on many more people. The technology used to develop and test the CoVid-19 vaccine will be similar but honestly, it will be at least a year before large scale trials can begin I would imagine. And remember, in a disease that for most people is very mild, if the vaccine has significant side effects in anything more than a tiny minority then its risks will outweigh its benefits
If people get infected are they then immune from further corona viruses
Again, not known, but based on SARS, probably some immunity but not life long
Making sense of CoVid-19 with Silman 