At least a million people die of malaria every year.  And one problem with treating the disease may be…treating the disease.  The current dosages of drugs used to fight malaria may sometimes make the problem worse—by allowing the malaria-causing parasites to become drug resistant faster.  That’s what evolutionary biologists said recently in the Proceedings of the National Academy of Sciences.

Various strains of malaria parasites compete with each other in an infected patient.  So parasites that are easier to kill actually help keep down the populations of hardier parasites.  But a big dose of drugs wipes out the weak players, leaving the field open to the resistant bugs.  Working with infected mice, the researchers found that more drugs and longer treatments tended to actually worsen the situation.  Current public health policies try to kill every last parasite.  But if the condition in people acts like it has in mice, a better idea may be to try to use the amount of medicine that will keep the person healthy—but will also let the parasites continue to duke it out with each other.

—Steve Mirsky