By Michael Le Page
Hospitals have set up testing areas for covid-19
Michael Cooper/PA Wire/PA Images
Think you might be infected with coronavirus? Here’s what to do and how the test works.
Because infected people may have anything from severe pneumonia to no symptoms at all, the only way to confirm that someone is infected is to test them for the virus.
If you suspect that you are infected, current official advice is that you shouldn’t go to a hospital or to a doctor. You could infect other people including much-needed healthcare workers. Contact your local health authority and follow their advice. In the UK, call 111 or go to this website.
Several countries including the UK are testing only people who have symptoms of covid-19 and have either been in close contact with someone confirmed to have the disease, or have been to an area with a widespread covid-19 outbreak.
These criteria can lead to cases being missed, because people don’t always know if, say, they have been in contact with a confirmed case. The US has said it wants testing to be more widely available, and some are calling for it to be free, as it already is in many countries including the UK.
But testing based on symptoms alone would be too broad, given covid-19 has similar symptoms to many common respiratory illness. “I am not sure what other criteria you could use,” says Mark Woolhouse of the University of Edinburgh, UK. “The symptoms are too non-specific; we’d end up testing millions of people.”
Based on 55,000 confirmed cases in China, 90 per cent of people with covid-19 develop a fever, 70 per cent have a dry cough, 40 per cent feel very tired and 30 per cent cough up sputum. Rarer symptoms include shortness of breath, sore throat, headache, muscle or joint pains, nausea or vomiting, blocked nose and diarrhoea.
Testing involves taking a swab of the nose or throat and samples of sputum if you are coughing it up. You may also have blood drawn and tested. This may be done at your home or in a drive-through site.
In the lab, technicians look for genetic sequences specific to the coronavirus. Because the virus’s genome is made of RNA, this involves first turning the RNA into DNA. Some labs say they have developed tests that can produce results in a little as three hours, but it will usually take longer to get results.
These tests are not entirely reliable. “One or more negative results do not rule out the possibility of covid-19 virus infection,” says the WHO guidance on lab testing.
This can be due to technical problems, such as not keeping samples refrigerated, but it also has to do with the nature of viral infections. Someone who has only just been infected may not yet be shedding the virus into the throat, while someone at a late stage may have stopped doing so, while still having an active infection in other parts of the body.
Looking for genetic sequences also cannot identify people who have been infected and fully recovered. Many labs are trying to develop tests for the antibodies our immune system produce to defend against the coronavirus, which our bodies keep making even after the virus is eliminated.
An antibody test could reveal whether or not lots of people get very mild infections that are going unnoticed. That would mean the case fatality rate could be significantly lower than the current estimate of around 1 or 2 per cent.
Finally, even if you think you only have a cold or flu, health providers often recommend that it is best to self-isolate if you can. Reducing the spread of other respiratory viruses will help ease the burden on health services, and make it easier to identify those who do have covid-19.
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By Michael Le Page