Communicable disease data provides information about the effectiveness of L.A. County’s public health programs. Over the last 10 years, the number of reported sexually transmitted diseases such as chlamydia, gonorrhea and syphilis has increased while the number of persons diagnosed with AIDS decreased. The exact reason for this remains a public debate. An increase in viral meningitis undoubtedly signals the advent of West Nile Encephalitis. Rubella, diphtheria and polio have virtually disappeared and cases of mumps, measles and tetanus have significantly declined.