1. Department of BiologyUniversity of Pittsburgh JohnstownJohnstownPennsylvania
2. Department of Infectious Diseases and MicrobiologyUniversity of PittsburghPittsburghPennsylvania
3. Department of EpidemiologyUniversity of PittsburghPittsburghPennsylvania
4. Tobago Health Studies Office, Scarborough, TobagoTrinidad and TobagoWest Indies
5. Department of PathologyUniversity of PittsburghPittsburghPennsylvania