-- and other pharmaceuticals -- in the developing world. If you go to the Karaikoo neighbourhood in Dar es Salaam, you'll find streets packed with tens of thousands of shoppers from across central Africa. Women wearing brightly-patterned skirts stuff cars full of jeans, shoe polish, and cell phones. Boys push carts loaded with boxes of sunglasses, purses, and radios.

Many of these shoppers stop at one of Karaikoo's dozens of mom-and-pop pharmacies. They load up on the imported pharmaceuticals inside –- drugs for pain relief, AIDS … and malaria. Shoppers will sell these drugs at a profit back in their home villages in Uganda, Rwanda, and Burundi.

As I stood in a pharmacy in Karaikoo, I realized this port city is actually a clearinghouse for dangerous fake drugs, pumping the illicit goods into the heart of Africa. And what struck me was that somewhere, there are people who are deliberately making these worthless pills, syrups and capsules. And they know their profits come at the expense of poverty, human suffering and death.

I interviewed the owners of five of Karaikoo's pharmacies. Each showed me paperwork -- tracing their purchases back through suppliers to Tanzania's Pharmacy Control Board. But what I discovered in Tanzania is that counterfeiting technology, corruption, and a lack of regulatory capacity means that fake drugs can make it past that regulatory body, and onto pharmacy shelves.

When imitation drugs are shipped alongside the real brand-name drugs, they often look exactly the same. From the moment they enter the port, no one, including Pharmacy Control Board officials, can tell the difference without testing each box in a laboratory.

Greased palms also get fake drugs onto the shelves. Suppliers of fake drugs may offer to sell pharmacists or retailers boxes of a particular brand-name drug at a price well below the going rate. Import and authenticity documents are forged. What I discovered is that no one ever SAYS these boxes of drugs are counterfeit -- it's a kind of "don't ask, don't tell" policy.

Finally, in a country as poor as Tanzania, there are very few officials who can police the import of such deadly commodities. Even though the government is taking steps to crack down on counterfeiters, there are just too many points of entry for illicit goods.

What do you think is the best way to prevent fake drugs from making their way into Africa's pharmacies?

Listen to Gretchen's story about fake malaria drugs in Tanzania.