SPF means “specific pathogen free.” SPF monkeys are free of specified infectious agents, including herpes B virus, type D retrovirus, simian immunodeficiency virus (the monkey form of HIV) and simian T-lymphotropic virus. Not only can these pathogens interfere with research results, monkeys carrying them pose risks to researchers and animal care staff. Certain types of AIDS research, in particular, require SPF animals. The CNPRC is striving to expand its SPF breeding colony for the health of the animals and the safety of Center personnel.