As winter draws in, the threat of flu looms large. But getting a preventative shot might not be the best line of defence any more — because new research suggests a small dose of crystal meth might be effective, too.

Researchers, from the National Health Research Institutes in Taiwan and the University of Regensburg in Germany, have been working together to investigate how methamphetamine interacts with different viral infections. Meth is a widely abused drug and there's a wealth of evidence which suggests chronic use can dramatically increase the risk of picking up viruses, because it suppresses the immune response of the body.

The researchers guessed the same would be true for influenza but, like all good scientists, they had to prove their hypothesis — so they set to testing it out. First, they took human lung cells and nurtured them in the lab, before exposing some of them to cystal meth. They then exposed the cells to the H1N1 influenza virus.

What they observed surprised them. Instead of increasing the rate of development and spread of the virus, meth seems to reduce susceptibility to flu. The results are published in PLoS One.

It's worth pointing out some major caveats here, of course. First, this is an experiment performed using just one strain of flu — we have no idea if meth would be protective against other types in he same way. Second, and perhaps most important, this in an entirely lab-based test: the experiments were performed in a Petri dishes of cells, not on real patients or animal models. And if you're looking for a third caveat, well, just watch Breaking Bad.

The fact remains, though, that the counter-intuitive finding is an interesting one. It certainly suggests that meth users may, weirdly, be at a lower risk of contracting flu than the rest of us. But more interestingly, it could be that compounds similar to meth could be used as effective anti-influenza treatments. Just don't self-prescribe yet, please. [PLoS One]

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