This new paper by Björkman-Nyqvist, Svensson, and Yanagizawa-Drott (August 2012) says:
We collect drug samples from a large set of local markets in Uganda using covert shoppers and employ Raman spectroscopy to test for drug quality. We find that 37 percent of the local outlets sell fake antimalarial drugs.What to do about it? [The World Health Organization estimates that they account for 30% of all medicines on sale, and kill up to 2,000 people daily worldwide].
. . . [T]he entry of high quality sellers [such as NGOs] decreased the share of fake drugs sold by the incumbents by approximately 50 percent.
Currently some people wrongly believe that malaria can be transmitted by interacting with infected people, or by eating fruits contaminated with mosquito eggs. This leads to misdiagnosis and to take fake medicine. Education can help eliminate the mistaken views.See here a social entrepreneur facing the problem.
[I can recognize the fake one?] Let's see:
The picture is taken from the paper.