1.1 History of poliomyelitis and vaccination against poliovirusThe first case of poliomyelitis in Korea was reported in 1939. The inactivated polio vaccine (IPV) and the oral polio vaccine (OPV) were introduced in 1958 and 1962 respectively, and the National Immunization Program (NIP), which was established in 1966, designated poliomyelitis as a second-class communicable disease. Until 1975 most vaccinations used both IPV and OPV, thereafter only OPV was used.The overall risk for vaccine-associated paralytic poliomyelitis is estimated to be approximately one per 2.4 million doses of OPV vaccine . One vaccine-associated paralytic poliomyelitis case was reported in Korea in 2003 . In 2004, the Korea Advisory Committee on Immunization Practices (KACIP) recommended the use of an IPV-only schedule in the NIP, and since then only IPV has been used in Korea.Polio vaccination is recommended at 2, 4 and 6 months of age with a booster dose at 4–6 years. The immunization rate for polio has been sustained at an estimated level of 90–95% since the 1980s.
1.2 Reported cases of poliomyelitis in KoreaAccording to a study conducted during 1962–1964, poliomyelitis cases were most prevalent in one-year-olds, and 70% of the cases were in children below 3 years of age . After polio vaccine was introduced in the 1960s, the incidence of poliomyelitis declined to 0.1/100,000 persons and the mortality rate decreased to 0.1–0.4% . After the five reported cases in 1983, no case of wild poliovirus infection has been reported in Korea up to 2010 (Table 1) .
1.3 National infectious disease surveillance and laboratory surveillance systemsAll notifiable vaccine-preventable diseases (VPD) are reported from public health centers, private clinics and hospitals to the Korea Centers for Disease Control and Prevention (KCDC) via a web-based system under the Prevention of Communicable Disease Act. The system is known as the Korea National Infectious Disease Surveillance (NIDS) system.NIDS is coupled with a laboratory surveillance system. Apart from reporting VPD cases to NIDS, for confirmatory testing public health centers, private clinics and hospitals can send various samples from patients suspected of having infectious diseases directly to the Korea National Institute of Health (KNIH) or indirectly through a provincial Research Institute of Public Health and Environment to the KNIH. The results of these tests are reported to the KCDC. A schematic flow chart of the NIDS and laboratory surveillance systems is shown in the Figure.
1.4 Surveillance of acute flaccid paralysisAn annual non-polio rate of acute flaccid paralysis (AFP) of ≥1/100,000 in children under 15 years of age is a requirement for certifying polio eradication in a country . Since 1998, AFP surveillance in Korea has been conducted every year with 70 reporting hospitals under the coordination of the KNIH . As of 2011, 50 sentinel hospitals, including all the pediatrician-training hospitals, are under surveillance.
1.5 Laboratory confirmation of poliomyelitisVirologic evaluation to confirm poliomyelitis consists of tests on two adequate stool specimens from each AFP patient collected 24–48 hours apart and within 14 days of onset of paralysis [8,9]. Laboratory confirmation of poliomyelitis is performed using a cell culture/neutralization test. The stool is further tested using real time reverse transcription polymerase chain reaction (RT-PCR) using pan-enterovirus , group-specific  and serotype-specific primer sets .
Response Plan Against Poliomyelitis OutbreakIn 2010, in response to the increased possibility of poliovirus importation because of a recent poliovirus outbreak in the European region, the Division of VPD Control and NIP of the KCDC prepared a response plan as a guide for key actions to be taken if a poliovirus outbreak occurs in the Republic of Korea.
￭ Because the Republic of Korea maintains a high immunization rate and has generally good sanitation, a poliomyelitis outbreak is unlikely to occur in the country.
￭ However, a single detected case of poliovirus infection would be considered as an outbreak and would initiate activation of the response plan.
￭ All decisions on the response to poliovirus detection will be made at the national level.
￭ Regular, timely and comprehensive information sharing with the public, relevant partners and international society is important.
2.2 Action planEach action is not necessarily separate from other actions; rather it is more likely that a number of actions will take place simultaneously. Response teams will be required at all levels of the public health system. The primary response will be driven at the jurisdiction level and coordination at the national level will be overseen by the KCDC.
2.2.1 Reporting suspected caseAny poliovirus isolated from a reported AFP case or any suspected poliovirus infection case reported through the NIDS will signal the immediate initiation of the actions described below.
2.2.2 Case investigationWithin 24 hours of a case being reported an epidemiological investigation will be initiated and, for virologic evaluation, stool specimens from every case will be sent to the national polio laboratory for testing. Epidemiological investigation will determine the likely source of the infection and indicate if the virus might have spread further. It will be essential to collect as much information as possible about the patient’s history including:
￭ Information about the patient, e.g. age and sex.
￭ Clinical course and laboratory testing.
￭ Immunization status of the patient.
￭ Exposure history (1): residence in or travel to a polio endemic country or to a country that has recently reported transmission of poliovirus or vaccine-derived poliovirus.
￭ Exposure history (2): contact with persons recently immunized with OPV, or with persons who have recently traveled to a polio endemic country or contact with persons who have traveled to a country that has recently reported importation of polio cases or vaccine-derived poliovirus or that uses OPV.
2.2.3 Expert meetingsWhen the case investigation is complete, the KCDC will convene an urgent meeting of the KACIP sub-committee for DTaP/polio vaccines to inform the advisory group of a possible polio outbreak. The sub-committee will review the results of the case investigation and check that all the necessary information has been obtained. The sub-committee will then decide what further information should be obtained and provide technical advice on what actions should be taken in response to the outbreak. When appropriate, the results of the meeting will be presented to KACIP members.Because a polio outbreak is a public health emergency of international concern under the International Health Regulations (IHR), the IHR Focal Point of Korea will immediately notify the World Health Organization of the situation.
2.2.4 Outbreak responseThe poliovirus outbreak response includes:
￭ Case isolation
￭ Management of potential contacts
￭ Cleaning and disinfecting
￭ Enhanced surveillance
￭ Risk communication
Case isolationIndividuals identified as or suspected of being infected with poliovirus will be isolated to reduce the risk of virus spread. The patient will be isolated from other patients in hospitals. Weekly stool specimens will be collected from the patient and tested in the national polio laboratory. Isolation can be terminated when two consecutive weekly stool samples are negative for poliovirus.Since poliovirus transmission is mainly person-to-person via the fecal-oral route, health care workers or other caregivers should follow contact precautions.
Management of potential contactsTo contain the spread of the virus, the relevant jurisdiction under the supervision of the higher-level organization will identify potential contacts of a patient and undertake appropriate measures. Potential contacts would be: 1) household contacts who lived with the patient and shared a toilet during the infectious period; 2) health care workers who cared for the patient during the infectious period; and 3) public contacts including toilet contacts who contacted or shared a toilet with the patient before the patient was isolated and the toilet was cleaned.
￭ Household contacts have the greatest risk of being exposed to poliovirus and should be isolated at home until it is proved that they are not infected. Stool specimens should be taken at least 3 days after first exposure to the index patient. Contacts can be released from quarantine when two stool samples taken 24–48 hours apart are negative for poliovirus.
￭ For health care workers who have been in close contact with the index patient and who have no recorded immunization history, or who are not yet completely vaccinated, two stool samples should be taken 24–48 hours apart, the first being taken at least 3 days after first exposure to the index patient.
￭ Public contacts will be provided with information on poliovirus infection, hygiene and vaccination. They will be informed that they might have been in contact with poliovirus and advised that they should immediately consult a public health center if they develop any symptom that could be attributed to poliovirus infection.