Last week (June 11) in the first of a three part series on the coronavirus crisis Dr Andrew Bamji set out the history of the event to date, and this week and next week he answers some of the most frequently asked questions.
Can you get SARS-CoV-2 without symptoms?
Yes. That means that you might be able to spread it because you didn’t know you had it.
How do you catch it?
From someone else’s cough droplets. That’s why masks are a sensible idea; you can’t cough over someone else, and if they cough over you, you have some protection. However, a contact tracing exercise in Singapore showed that a church congregation picked it up directly from an infected couple (who didn’t know they were infected) but also that the couple who sat in the same seats for a later service also acquired it. This shows that the virus can hang about on surfaces for a while. That’s why handwashing is important too. And gloves.
What symptoms does SARS-CoV-2 cause?
Dry cough, fever and loss of smell (anosmia) are important ones. You won’t know that your blood oxygen levels are falling due to lung involvement until very late, because (unusually for this problem) it doesn’t make you breathless to begin with. However a low blood oxygen is highly important in terms of seeking medical advice. The blood oxygen level can be measured with a simple and inexpensive device called a pulse oximeter. Every surgery and care home should have one or more; you can get your own on the internet.
How do you test for Covid-19?
If you think you might have the illness acutely, you get a test showing you have active infection. This is the antigen test. However, there are false negatives, so it is not entirely reliable. If you think you have had it already and recovered, an antibody test may prove this, but again a negative test is inconclusive. This is why social distancing measures are important; whether you have it or not, you won’t spread it if you are far enough apart.
Why are some groups more likely to die than others?
As yet we don’t know. The elderly are at high risk, as are the obese, those with diabetes or underlying lung or heart disease, and some ethnic groups are at high risk too. This may be a combination of changes in the immune system as one ages or from hormonal effects, or genetic differences that allow the virus to infect cells more easily. It’s also possible that close social interactions (for example, within large family groups or religious services) may play a part in worsening transmission, but probably doesn’t explain the higher death rate.
The BAME issue has become a hot potato, but a breakdown of risk indicates that the highest risk is in people from Bangladesh and Pakistan, but not India. The risk in people of African origin is high, but not as high as the Bangladeshi group. We don’t know enough yet to understand all of this. It may take years of analysis.
Can children get sick from SARS-CoV-2?
Yes, but it’s very rare. It causes a condition similar to one seen in paediatric rheumatology clinics, called Kawasaki disease, which is due to blood vessel inflammation (vasculitis) which is treatable. It also appears that children do not transmit SARS-CoV-2. Why not? We don’t know yet.
What actually happens in Covid-19 disease?
The virus latches onto a cell receptor called ACE-2. These receptors are found widely in many surface cells, or epithelial cells. The virus then gets into these cells, and makes them leak, rather like popping a water-filled balloon. The cells lose fluid and cannot function properly. In the nose the smell receptors go. In the lungs fluid leaks into the air spaces. The body’s immune system then goes into overdrive and releases large amounts of inflammatory chemicals, called cytokines, setting off a chain reaction throughout the body which results in abnormal blood clotting, heart muscle damage, gut leakage and kidney failure.
Why do so many people who go onto ventilators die?
The lung damage caused by the virus and the cytokine storm means the lung lining cells cannot transfer oxygen to the blood; also the red blood cells cannot pick it up, because they too are damaged. Forcing more oxygen in, when a patient is very severely affected, simply does not work. Patients bad enough to need ventilation in an ICU are the very sickest; even without having Covid-19, the mortality in ventilated ICU patients is high.
So why was there this rush to have more ventilators?
We didn’t understand what was happening in the lungs. It’s different from most infections and blood clots, but initially it was thought to be similar. And better safe than sorry. On the positive side it shows what can be done quickly in a crisis.
Next week Andrew continues to answer your questions and may have some up to date comments on where we have now got to with the crisis.
