The importance of testing for virus

Dear Sir,

In response to your plea for content in last week's Chronicle, I am happy to share my thoughts on the importance of testing in the context of the coronavirus pandemic.

I am no specialist and will gladly retract this letter in response to those more recently and closely involved in the virology and immunology of the infection.

There are two types of testing, that of isolating the virus or its products from the throat and nose, and testing for antibodies to the virus.

The first confirms that the person was, at the time of testing, carrying the virus and in the presence of relevant symptoms it is reasonable to assume that it is responsible for them in the context of the present pandemic.

The second shows that the person has been exposed to the virus and mounted an antibody response.

As the virus is a recent intruder into our human domain there does not seem to be a need for a second test that is usually needed to confirm a recent infection.

Usually a reasonable titre of antibodies implies that the person is no longer infectious and is immune, though this would need verifying for this particular virus.

If this is true, it becomes obvious how important testing is of people at risk and suspicion of carrying the virus to confirm the diagnosis and reassure those testing negative.

A positive antibody test would imply that the person is not able to transmit or receive the infection for a period, allowing them to resume normal activities.

There is also the epidemiological importance of measuring antibodies in the wider population that will give guidance as to how many in it have been exposed and are no longer infectious.

All tests have a variety of possible errors so might need repeating or confirming with another test as well as errors in assigning the test to the person along the route from collection to explaining the result.

Yours faithfully,

(DR) PETER HIRST