Epidemiology and molecular epidemiology of bacterial pathogens, including Escherichia coli 0157:H7, Streptococcus pneumoniae, group B Streptococcus, and Neisseria meningitidis; epidemiology and vaccine prevention of HIV infection in Brazil; enhanced surveillance methods for the detection of naturally-occurring and bioterrorism-related outbreaks Research Summary A major focus of Dr. Harrison's work during the past few years has been in the use of molecular epidemiology to understand how certain infectious diseases spread and are transmitted. Ongoing studies involve understanding how Streptococcus pneumoniae spreads within populations, correlating the changing epidemiology of meningococcal disease with the strains of Neisseria meningitidis causing invasive infections, and identifying areas of DNA sequence diversity in Escherichia coli 0157:H7 that can be exploited for outbreak detection. Current methods being used include pulsed-field gel electrophoresis, PCR, multi-locus sequence typing, and typing using variable number tandem repeats.