Meningococcal disease. Secondary attack rate and chemoprophylaxis in the United States, 1974.

Three hundred twenty-six reported cases of meningococcal disease in the United States from November 1973 through March 1974 were investigated. Three household members became ill with meningococcal disease following onset of the initial case in their household. The secondary attack rate was approximately 3/1,000 household members. In 60% of the households, members were given an antimicrobial drug as chemoprophylaxis for meningococcal disease, but only 35% received minocycline hydrochloride or rifampin, the two drugs now available for the eradication of sulfonamide-resistant meningococci from the nasopharynx. Only 26% given chemoprophylaxis received the drug within 24 hours after the patient's hospital admission. Survey results indicate that the secondary attack rate of meningococcal disease may justify the use of chemoprophylaxis, but that frequently in the United States, the drugs given are likely to be ineffective, give too late, or administered to persons who are not at high risk to meningococcal disease.