There's an interesting article published in Science: "Permissive Secondary Mutations Enable the Evolution of Influenza Oseltamivir Resistance" (Science 328:1272, 2010). Oseltamivir is the flu antiviral drug that is also known as Tamiflu. What's interesting about this article is that the resistance to Tamiflu partly became prevalent in the seasonal H1N1 influenza strain because two other mutations allowed the Tamiflu-resistant virus to effectively infect cells. A lot of times, antiviral mutations often make the viruses less potent. The drugs target an important enzyme for the virus and the mutations need to occur at the site in the enzyme that interacts with the drug for resistance to develop - and this is often the same site that the enzyme needs to function properly - and hence the mutations will make the enzyme not work as well. Even more interesting is that the resistance to Tamiflu came about in the absence of widespread use of the drug and therefore there was little selection for drug-resistant viruses.
Now this is a bit more scientific than what I have written here; what brought this post about is a statement in an accompanying article in the same issue of Science. Science will often solicit short reviews (called Perspectives) of papers published in this journal. The reviews are written so that a wider audience can understand and appreciate the research published in the journal. And these reviews are often very well written. I have even used them in my classes to give students a view of research that is on-going on the topics they are studying in class.
But what was puzzling was this statement in the accompanying review to the paper above: "More puzzling, drug resistance can occur in the absence of the main agent of selection". This is a common misperception of a lot of people - and surprising to be written by a prof at Penn State. Mutations occur all the time – and agents of selection (antivirals and antibiotics) don’t cause mutations – but SELECT the mutants that have arisen! This is how drug resistance in viruses occurs - first there is the mutation and then in the presence of the antiviral (which is killing all the non-resistant viruses) the resistant virus becomes the predominant virus. I think the point that the author was trying to make was the fact that the antiviral resistant virus has become the predominant virus in the absence of drug selection. But this isn't what was stated in the sentence above - the author did come around to his conclusion - but he did so after making an erroneous statement.
Now a few people might think - so what? Well I have a little pet peeve about good writing and proper grammar (heck I've gone through my previously published blog posts and corrected myself!). I tell my students that using the correct words (I work with a lot of undergrads) and speaking and writing clearly are the only way to make sure people understand what you are talking (or writing) about. And this is a good example of how - what looks like a well written sentence - is actually wrong information!
Just my 2 cents. :)