[Meningococcal disease: always present. Serogroup changes in the Southern Cone].

Meningococcal disease (MD) caused by Neisseria meningitidis is a condition with high mortality rates in childhood. Serogroup W135 N. meningitidis (MenW135) is usually associated with 1 to 8% of MD cases worldwide, and with a low carriage rate. During March 2000, an increase in the number of cases of MenW135 in Saudi Arabia was reported that coincided with the Hajj pilgrimage (Hajj-2000 strain). Mayer et al studied MenW135 strains from outbreaks related with this pilgrimage and found that all had been caused by the same hypervirulent clone (ST-11/complex ET-37). The circulation of this strain could also be documented in Latin America. In the last years, changes in serogroup prevalence have been observed in the region, the increase of MenW135 in the Southern Cone being the most significant. N. meningitidis infections of several serogroups including MenW135 may be prevented with chemoprophylaxis with antibiotics and quadrivalent vaccines. Better knowledge of the global epidemiology through the new molecular techniques, jointly with the availability of vaccines are the most relevant tools to control hyperendemic or epidemic periods of MD.