ESR scientist Dr Wendy Williamson describes some of the difficulties she has to overcome in developing a method for detecting viruses in our waterways. Detecting viruses in the environment is very difficult because there are so many different types of viruses present and they are often in very low numbers.
DR WENDY WILLIAMSON
In general, when you are looking at viruses from medical samples, they… the diversity of viruses – that is, the different types of viruses you are likely to find in a sample – are relatively small. If the person has an infection, they are likely to have only one or two types of viruses – likely to have – but the number of viruses that they have are likely to be really high. So the biodiversity is low, but the actual numbers are likely to be high. That means that your detection ability is greatly increased, because you have lots and lots of viruses, and they are likely to be of only a few different types. When you move into the environment, you have exactly the reverse, the biodiversity of viruses is extremely high, because you have viruses there from humans, animals, plants, bacteria, but the actual numbers of viruses are extremely low. So diversity high, numbers low, which means, in order to actually detect a virus, you have to take it from the sample and get it into a test tube in the laboratory. And that is the real problem we have with viruses is actually getting them concentrated enough to be able to detect them. And that means we have to filter or sample very, very large volumes of water in order to concentrate our viruses, to such an extent that we can then have a good probability of actually getting it into our tube. So you could have a bathful with only a teaspoon of viruses in, so to speak, and you have to get that whole teaspoon of viruses into your test tube to be able to quantify them. And you have to filter the whole bath water, because if you only filtered a little wee bit of the bath water, you would only have one virus in there and that may be below the ability of our assays to actually detect it.
Lassa, Influenza, and Coronavirus virus micrographs from F.A. Murphy, School of Veterinary Medicine, University of California, Davis.