Academic journal article Bulletin of the World Health Organization

Poliomyelitis Surveillance in Shandong Province, China, 1990-92

Academic journal article Bulletin of the World Health Organization

Poliomyelitis Surveillance in Shandong Province, China, 1990-92

Article excerpt

Introduction

In China, poliomyelitis was well controlled until the mid-1980s by the development of immunization services supported by the Expanded Programme on Immunization (EPI).(a,b) However, in 1988, outbreaks occurred in the provinces on the east coast of the country, and nationwide outbreaks followed in 1989 and 1990. Shandong Province reported 200-500 cases annually over the period 1988-90, and approximately 5000 cases were reported nationally in each of 1989 and 1990. The epidemiological characteristics of the outbreaks in Shandong Province have been described previously (1).

Through supplementary immunization activities and nationwide efforts, the numbers of poliomyelitis cases have been steadily reduced in many provinces. In Shandong Province, mass campaigns were launched in January 1991 to immunize as many under-4-year-olds as possible with oral poliovirus vaccine (OPV). As a prerequisite for evaluating the interruption of wild poliovirus transmission the quality of poliomyelitis surveillance itself had to be thoroughly reviewed.

The poliomyelitis surveillance programme in Shandong Province included the immediate reporting of cases of acute flaccid paralysis (AFP), case studies involving laboratory investigation, and the monitoring of surveillance indicators (1). We describe here the recent status of poliomyelitis eradication in the province, with particular reference to AFP surveillance and laboratory investigations.

Methods

Until 1990, confirmation of poliomyelitis cases in China was based on a case definition prepared by the Ministry of Public Health in accordance with the original WHO definition.(c) Most cases lacked laboratory confirmation because stool specimens were unavailable; poliomyelitis was considered to be confirmed if any residual neurological sequelae were present 60 or more days after their onset. From 1991 onwards, a specific diagnosis was given in cases of non-poliomyelitis AFP after examination by a neurologist.

Before early 1991, when the system for the immediate reporting of AFP was introduced, no independent channel for the notification of poliomyelitis existed in Shandong Province: poliomyelitis reporting was undertaken as part of the general surveillance activities for communicable diseases. AFP reporting aimed to detect all cases of sudden-onset flaccid paralysis except those caused by injury or other immediately identifiable factors. Local epidemic prevention stations were requested to initiate case investigations within 24 hours of notification. If flaccid paralysis occurred, the stations immediately reported the cases to the central level and began to collect specimens for laboratory investigations. Some essential components of this action have been monitored using previously described indicators (1).

Statistics for the estimation of the baseline levels of AFP incidence in children were not available in Shandong prior to 1991. In 1992, in order to obtain information on the types and incidence of AFP, a retrospective study was carried out in four general hospitals, a children's hospital, and an infectious diseases hospital in Jinan City, the provincial capital. The staff of the provincial epidemic prevention station reviewed patients' records for 1991 in paediatric departments and other units concerned with childhood infectious diseases or neurology. Since there were few records for some of the AFP cases, because they had only attended outpatient clinics, we attempted to support documented diagnoses either by comparison with records in the provincial epidemic prevention station or by follow-up through the station networks.

In China, only children aged [less than or equal to]12 years attend paediatric clinics. A survey covering older children would have required much extra work and would probably have yielded very little additional information. Investigations were therefore confined to children aged [less than or equal to]12 years. …

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