Progress Toward Poliomyelitis Eradication -- South East Asia Region, 1988-1994

Since the adoption of the poliomyelitis eradication initiative by the World Health Organization (WHO) in 1988, substantial progress toward the eradication of polio has been achieved in the Region of the Americas and in the Western Pacific Region of WHO (1-3). A major step toward global eradication was made in 1994, when polio eradication activities -- specifically the implementation of biannual National Immunization Days * (NIDs) -- were accelerated in the member countries of the South East Asia Region (SEAR) of WHO ** . In August 1994, Thailand became the first SEAR country to conduct NIDs; by February 1996, seven of the 10 member countries will have conducted NIDs. This report summarizes progress toward the eradication of polio in SEAR countries from 1988 though 1994 and is based on data reported through June 1995. Regional Summary

From 1988 through 1994, the number of paralytic polio cases reported in the region decreased by 82%, from 25,711 cases to 4373 cases Figure_1; however, in 1994, cases reported from SEAR accounted for 58% of the total number of paralytic polio cases reported worldwide. Within SEAR, during 1994, four subcontinent countries -- Bangladesh, India, Myanmar, and Nepal -- accounted for 4368 (99%) of the 4373 reported cases.

By 1994, five (Bangladesh, Indonesia, Nepal, Sri Lanka, and Thailand) of the 10 member countries were conducting surveillance for acute flaccid paralysis (AFP) *** Table_1 (3). Of these five countries, Sri Lanka and Thailand routinely conducted surveillance for both AFP and wild polioviruses. India

Regional progress toward eradication primarily reflects achievements in India, where reported polio cases declined 83% during 1988-1994, from 24,257 to 4052, respectively. During 1992-1994, the median age of persons with polio was 18 months, the same median age as in the early 1980s (4). The proportion of persons aged less than 3 years with polio ranged from 79% in 1992 to 82% in 1993 and 1994; the proportion aged less than 4 years ranged from 88% in 1992 to 91% in 1993.

In 1993, stool specimens were collected for viral culture from 604 (14%) of 4236 reported polio cases; polioviruses were isolated from the specimens for 193 (32%) cases. Of the 193 polioviruses isolated, 46 (24%) were wild poliovirus type 1; 46 (24%), wild poliovirus type 2; 59 (31%), wild poliovirus type 3; 34 (18%), a mixture of at least two types; and eight (4%), unknown. In 1994, stool specimens were collected for viral culture from 1075 (27%) of 4052 reported cases; polioviruses were isolated from the specimens for 397 (37%) cases. Of the 397 polioviruses isolated, 299 (75%) were type 1; 35 (9%), type 2; 42 (11%), type 3; and 21 (5%), a mixture. The proportion of cases with type 2 poliovirus isolates decreased from 24% in 1993 to 11% in 1994.

The first NIDs in India ("Pulse Polio Immunization Days") will be conducted on December 9, 1995, and January 20, 1996, with a target of vaccinating approximately 75 million children aged less than 3 years with one dose of oral poliovirus vaccine (OPV) in each of two rounds. Bangladesh

In 1994, Bangladesh reported 289 cases of polio, a 46% decline from the 540 cases reported in 1988. In 1993, stool specimens were collected for viral culture from 61 (26%) of 233 AFP cases; polioviruses were isolated from the specimens for 17 (28%) cases. Of the 17 polioviruses isolated, 16 (94%) were type 1, and one (6%) was type 2. In 1994, stool specimens were collected for viral culture from 123 (43%) of 289 AFP cases; polioviruses were isolated from the specimens for nine (7%) cases. Of the nine polioviruses isolated, six (67%) were type 1, and three (33%) were type 3.

During March-April 1995, Bangladesh conducted its first NIDs. Of the 19.8 million children aged less than 5 years in the country, 90% received at least one dose of OPV, and 83% received two doses. Myanmar

In 1994, Myanmar reported 25 polio cases, a 58% decline from the 60 cases reported in 1988. Vaccination coverage levels with three doses of OPV at age 1 year increased from 10% in 1987 to 77% in 1994.

The first NIDs in Myanmar will be conducted on February 10 and March 10, 1996. Because China, an adjacent country that has nearly eliminated polio, will be conducting NIDs for the third consecutive year during December 1995-January 1996, the implementation of NIDs in Myanmar in early 1996 is critical to the expansion of the polio-free zones in neighboring countries. Nepal

In 1986, the government of Nepal intensified its vaccination program by implementing the Universal Childhood Immunization project. From 1986 through 1990, reported coverage with three doses of OPV among children aged 1 year had increased from 34% to 74%; however, by 1994, coverage had gradually declined to 64%.

Nepal reported nine polio cases in 1988, compared with two cases in 1994. In 1994, the reported rate of AFP was 0.05 cases per 100,000 children aged less than 15 years Table_1. Indonesia

In 1994, Indonesia reported nine polio cases, a 99% decline from the 773 cases reported in 1988. Because AFP reporting was not implemented until 1994, estimated rates of AFP through 1994 were low Table_1. In 1993, stool specimens were collected for viral culture from four AFP cases; poliovirus was isolated from the specimen of one case. In 1994, stool specimens were collected from viral culture from 13 AFP cases; wild poliovirus type 1 was isolated from the specimen of one case.

In September 1995, Indonesia conducted its first NIDs. Because the population of the country is dispersed among approximately 3000 islands, NIDs were conducted during a 1-week period. Preliminary reports indicate that greater than 95% of all children aged less than 5 years received OPV during the campaign. Thailand

In 1994, Thailand reported one polio case, a decline of 91% from the 11 cases reported in 1988. Reported rates of AFP cases per 100,000 persons aged less than 15 years were 0.5 (1992), 1.0 (1993), and 0.6 (1994). Stool specimens for viral culture were collected from 151 (94%) of the 161 AFP cases reported in 1993 and 90 (92%) of the 98 AFP cases reported in 1994. The percentage of AFP cases with at least two stool specimens collected within 14 days of onset of paralysis increased from 37% in 1992 to 53% in 1994.

Of 11 specimens from culture-confirmed polio cases reported in 1993, five were type 1; two, type 2; and four, type 3. The last reported culture-confirmed case of polio occurred in June 1994 and was associated with type 1 wild poliovirus. In 1994, poliovirus was isolated from three other AFP cases; all were vaccine-related polioviruses, one each of types 1, 2, and 3.

In August 1994, Thailand accelerated efforts to eradicate polio by conducting the first NIDs in the region; approximately 95% of the 5.3 million children aged less than 5 years were vaccinated. Sri Lanka

In 1994, Sri Lanka reported no cases of polio, compared with 16 cases in 1988. During 1992-1994, the annual rate of AFP exceeded 1.0 cases per 100,000 persons aged less than 15 years (1.4 in 1992, 1.6 in 1993, and 1.4 in 1994). The percentage of AFP cases for which two stools were collected within 14 days of paralysis onset increased from 27% in 1992 to 69% in 1994.

The last culture-confirmed case of polio in Sri Lanka occurred in November 1993 and was associated with wild poliovirus type 1. In 1994, stool specimens were collected for viral culture from 80 AFP cases; only a vaccine-related type 2 poliovirus was isolated from the specimen of one case. The first NIDs in Sri Lanka will be conducted on November 4 and December 9, 1995, with a target of vaccinating approximately 1.8 million children aged less than 5 years. Mongolia

Mongolia reported no polio cases in 1994, compared with one case in 1988. In 1993, stool specimens were collected for viral culture from one AFP case; poliovirus was not isolated. In 1994, stool specimens were collected for viral culture from 26 AFP cases; one specimen was positive for wild poliovirus type 1. Bhutan, Democratic People's Republic of Korea, and Maldives

Three countries in the region -- Bhutan, Democratic People's Republic of Korea, and Maldives -- reported no polio cases during 1989-1994, which suggests that wild poliovirus transmission has been interrupted. However, in addition to interruption of wild poliovirus transmission for at least 3 years, certification of polio eradication requires adequate AFP surveillance, which has not been implemented in these countries.

Reported by: Expanded Program on Immunization, South East Asia Regional Office, World Health Organization, New Delhi, India. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Polio Eradication Activity, National Immunization Program, CDC.

Editorial Note

Editorial Note: The findings in this report document substantial progress toward polio eradication in SEAR, with an 82% reduction in annual reported cases during 1988-1994. Although wild poliovirus infection is endemic in at least seven (Bangladesh, India, Indonesia, Myanmar, Nepal, Sri Lanka, and Thailand) of the 10 countries of SEAR, six of these seven countries plan to have conducted NIDs by February 1996. Despite this progress, member countries of SEAR reported 4373 polio cases in 1994, accounting for 58% of the global total. This region and sub-Saharan Africa are the two persistent and major reservoirs of polio worldwide (2).

Worldwide eradication of wild poliovirus requires the implementation of NIDs and the establishment and maintenance of strong AFP surveillance systems in polio-endemic countries (5). In the Americas, eradication of wild poliovirus was accomplished primarily by targeting NIDs to children aged less than 5 years in polio-endemic countries during the low season of transmission (1). Rapid mass vaccination of children with OPV effectively interrupts community transmission of wild poliovirus (6). Further progress in SEAR is contingent on the identification of sufficient resources -- in addition to those provided by international organizations such as WHO, the United Nations Children's Fund (UNICEF), and Rotary International -- to implement NIDs. In India, upcoming Pulse Polio Immunization Days will be restricted to children aged less than 3 years because of financial and operational constraints to including additional birth cohorts of approximately 25 million children each. Because recent surveillance data suggest that 8%-9% of reported polio cases occur in children aged 3 years, inclusion of these children in future NIDs will be critical. Because most polio cases in the world are reported from SEAR, the ability of member countries in the region to strengthen integrated AFP and virologic surveillance will be critical to the success of the global polio eradication initiative (7).

References

1. de Quadros CA, Andrus JK, Olive J-M, de Macedo CG, Henderson DA. Polio eradication from the Western Hemisphere. Annu Rev Publ Health 1992;13:239-52.

2. World Health Organization. Progress towards poliomyelitis eradication, 1994. Wkly Epidemiol Rec 1995;70:97-104.

3. Yang B, Zhang J, Otten MW, et al. Eradication of poliomyelitis: progress in the People's Republic of China. Pediatr Infect Dis J 1995;14:308-14.

4. Basu RN, Sokhey J. Prevalence of poliomyelitis in India. Indian J Pediatr 1984;51:515-9.

5. Andrus JK, de Quadros CA, Olive J-M. The surveillance challenge: final stages of eradication of poliomyelitis in the Americas. MMWR 1992;41(no. SS-1):21-6.

6. Sabin AB, Ramos-Alvarez M, Alvarez-Amezquita J, et al. Live, orally given poliovirus vaccine: effects of rapid mass immunization on population under conditions of massive enteric infection with other viruses. JAMA 1960;173:1521-6.

7. Cochi SL, Orenstein WA. Commentary: China's giant step toward the global eradication of poliomyelitis. Pediatr Infect Dis J 1995;14:315-6.

* Mass campaigns over a short period (days to weeks) in which two doses of oral poliovirus vaccine are administered to all children in the target age group, regardless of prior vaccination history, with an interval of 4-6 weeks between doses.

** Member countries of SEAR are Bangladesh, Bhutan, Democratic People's Republic of Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, and Thailand. Mongolia, formerly a member country, was administratively transferred in 1995 to the Western Pacific Region of WHO; this report includes data for Mongolia through 1994.

*** Any case of AFP in a person aged less than 15 years is reported as a suspected case of polio. Effective AFP surveillance can detect an annual incidence of at least one case of AFP per 100,000 persons aged less than 15 years.

TABLE 1. Incidence rate * of reported acute flaccid paralysis (AFP) among persons aged
<15 years in countries conducting AFP surveillance +, by year -- South East Asia
Region (SEAR), & World Health Organization (WHO), 1991-1994
========================================================================================
                                                       % Reported cases in 1994
                                                       for which stool specimens
Country            1991     1992     1993     1994    collected  for viral culture
----------------------------------------------------------------------------------------
Bangladesh         0.59     0.42      0.46    0.56                 29
Indonesia @        0.30     0.20     <0.01    0.01                 --
Nepal              0.15     0.15     <0.05    0.05                 50
Sri Lanka          1.20     1.40      1.60    1.40                 69 **
Thailand            --      0.53      1.01    0.61                 53 **
----------------------------------------------------------------------------------------
*  Cases per 100,000 persons aged <15 years.
+  Surveillance indicators are routinely used to monitor the performance of reporting
   and investigation of AFP cases. In addition to AFP reporting rates per 100,000
   persons aged <15 years, the percentage of AFP cases with virologic investigation and
   the percentage with two stool cultures collected within 14 days of paralysis onset
   are examples of indicators used to monitor performance of surveillance.
&  Member countries of SEAR are Bangladesh, Bhutan, Democratic People's Republic of
   Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, and Thailand. Mongolia,
   formerly a member country, was administratively transferred in 1995 to the Western
   Pacific Region of WHO; this report includes data for Mongolia through 1994.
@  Rates calculated retrospectively. AFP reporting initiated in 1995.
** Percentage of cases with two stool cultures collected <14 days after paralysis onset.
========================================================================================

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