Epidemiology of poliomyelitis in Karachi,Pakistan: Prospective studies during 1990–93

Between October 1989 and September 1993, 245 cases of poliomyelitis visited the Department of Pediatrics, Civil Hospital Karachi, Pakistan. The majority of them were between 6 months and 2 years of age and the epidemic occurred during the hot season. The dominant serotype was polio type 1. All of the polioviruses isolated from the patients were wild type. Virological studies also disclosed that enteroviruses other than polioviruses were prevalent among healthy children as well as diarrheal and polio patients. Serodiagnosis by poliovirus-specific immunoglobulin M antibody tests using the capture enzyme-linked immunosorbent assay method were in good agreement with the results of virus isolation. The present study demonstrated that Pakistan is a region endemic for wild poliovirus and more aggressive preventive measures are needed to eradicate poliomyelitis from the region.     

Virological and serological studies on poliomyelitis in Karachi,Pakistan. I. Outbreaks in 1990-91

Between October 1989 and September 1991, 124 cases of poliomyelitis visited the Department of Paediatrics, Civil Hospital Karachi, Pakistan. The majority of them were between 6 months and 2 years of age and the epidemics occurred during the hot seasons. The dominant serotype was poliovirus type 1 during the epidemic season in 1990 and type 2 in 1991. All the polioviruses isolated from the patients were wild-type. Virological studies also disclosed that enteroviruses other than polioviruses were prevalent among healthy children as well as among diarrheal and polio patients. A serological survey to elucidate the serological efficacy of oral polio vaccine (OPV) showed that: (i) in 112 unimmunized children, after disappearance of transplacental maternal antibody during early infancy, antibody prevalence increased gradually and > 80% of the children were seropositive against all three types of polioviruses at 5 years of age; (ii) in 201 children immunized with full doses of OPV in their infancy, the decrease in antibody titer during infancy was less and seroprevalence rose sharply afterwards: at 2 years of age, > 80% of them were seropositive against all three types of the virus. The rapid increase of seroprevalence might be the effect of OPV administration. However, the prevalence was lower than that in developed countries.