Half of the children in Africa that die before the age of 5 die from complications from malaria.
Finally, these animals are important in studies of hepatitis B and C. Although there is now a vaccine for hepatitis B, these diseases remain a big problem. Tamarins were very important in the development of hepatitis A vaccine, and they may provide answers to some questions about hepatitis C. It is hard to determine numbers for the impact of hepatitis B and C worldwide, but it is probably on the order of 3 million or more people, and people who survive with hepatitis C for 25 years have a very, very high incidence of hepatocellular carcinoma and hepatomas. So it is also a risk factor in cancer.
I want to thank Jim Taylor, Don Bordine, and Alfie Caesar, who helped me with some numbers, as well as Larry Williams and Laura Zapalac in my department.