Progress Toward Poliomyelitis Eradication -- South East Asia Region, 1997-1998

In 1988, the World Health Assembly resolved to eradicate poliomyelitis by 2000 (1). To achieve this goal, in 1994 World Health Organization (WHO) South East Asia Region (SEAR) member countries * accelerated implementation of polio eradication strategies (2). In 1994, Thailand became the region's first country to initiate National Immunization Days (NIDs) **, followed by Bangladesh, Bhutan, India, Indonesia, and Sri Lanka (1995); Myanmar and Nepal (1996); and Democratic People's Republic (DPR) of Korea and Maldives (1997) (3-6). This report summarizes the progress in achieving routine and supplemental vaccination coverage and surveillance for cases of acute flaccid paralysis (AFP) and the impact of these activities on polio eradication in the region.

Since 1990, eight SEAR countries reported reaching the universal goal of greater than 80% vaccination of children aged less than 1 year with one dose of measles-containing vaccine, three doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP3), and three doses of oral poliovirus vaccine (OPV3). In 1997, all countries except Nepal (where coverage was 78%) reported greater than 80% routine coverage of children aged 12-23 months with OPV3.

In 1996, Bangladesh, China, India, Myanmar, Nepal, Pakistan, and Thailand held NIDs in December 1996 and January 1997, the low season for poliovirus transmission (3). This effort resulted in vaccination of approximately 243 million (approximately 38%) of the world's children aged less than 5 years. Other synchronized NIDs were repeated in 1997 and 1998 with intensified activities along the Myanmar-China border. In India, biannual NIDs reached from approximately 79 million children in 1995 to approximately 134 million in 1998 (5), the largest public health campaigns conducted in a single country.

AFP surveillance is conducted to identify all possible poliovirus cases to target supplemental vaccination activities. Surveillance relies on establishing an organized facility-based network of reporting units dispersed throughout a country. Epidemiolgic and virologic information is collected from each reported AFP case. Virologic support is provided by a network of 16 WHO-accredited laboratories in SEAR (nine in India, three in Indonesia, and one each in Bangladesh, Myanmar, Sri Lanka, and Thailand) Four of these laboratories also conduct intratypic differentiation to determine wild and vaccine-derived strains of poliovirus. The results of virus isolation and clinical follow-up studies are used to classify AFP cases as polio or nonpolio. AFP surveillance is evaluated by two key indicators: the sensitivity of reporting (target: nonpolio AFP rate of at least 1.0 case per 100,000 children aged less than 15 years), and the completeness of specimen collection (target: two adequate stool specimens from at least 80% of persons with AFP).

In 1993, the Regional Polio Laboratory Network was established in SEAR. In 1997, the posting of national surveillance medical officers in Bangladesh (five in 1995), Indonesia (seven in 1997), India (59 in 1997 and an additional 27 in 1998), and Nepal (five in 1998) substantially strengthened AFP surveillance in this region, especially in India where performance targets were reached within 1 year (5).

Since the early 1990s, Sri Lanka consistently has reported an annual nonpolio AFP rate of at least 1.0 (2). A nonpolio AFP rate of at least 1.0 also has been reached in Indonesia (1997), India (1998), and Thailand (1998). In 1998, the percentage of AFP cases with two adequate stool specimens collected for virologic culture within 14 days of paralysis onset reached 60% in India, 69% in Myanmar, 78% in Indonesia, 79% in Thailand, and 82% in Sri Lanka. Bhutan, Maldives, and Sri Lanka have had no wild poliovirus isolates for approximately 5 years.

AFP surveillance is less developed in Nepal and Bangladesh (Table_1). The nonpolio AFP rate in Nepal was 0.36 in 1998 compared with 0.26 in 1997, in Bangladesh it was 0.27 in 1998 compared with 0.14 in 1997, and in DPR Korea no cases of AFP were reported in 1998 compared with three in 1997.

From 1997 to 1998, reported polio cases increased in Bangladesh (from 171 cases to 266 cases), Bhutan (from no cases to two cases), India (from 2278 cases to 3323 cases), and Thailand (from 19 cases to 25 cases). During the same period, reported polio cases decreased in Indonesia (from 293 cases to 91 cases) and Myanmar (from 55 cases to 31 cases). In 1997 and 1998, DPR Korea, Maldives, and Sri Lanka reported no polio cases (Figure_1).

In 1998, wild poliovirus types 1 and 3 were isolated only in Bangladesh and India. In 1997, no wild poliovirus type 3 was isolated in Bangladesh. In India, both wild types 1 and 3 continued to circulate widely, but preliminary results of DNA sequencing indicate a substantial reduction in their genetic biodiversity (5). Wild poliovirus type 2 was last isolated in 1998 in Uttar Pradesh and Bihar, India. Despite improved surveillance, wild poliovirus was last isolated in Sri Lanka in 1993, in Indonesia in 1995, in Myanmar in 1996, and in Thailand in 1997.

Reported by: Regional Office for South East Asia, New Delhi, India. Global Program for Vaccines and Immunization, World Health Organization, Geneva, Switzerland. Respiratory and Enterovirus Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Vaccine Preventable Disease Eradication Div, National Immunization Program, CDC.

Editorial Note

Editorial Note: SEAR contains approximately 25% of the world's population, including the largest country where polio is endemic, India. Progress in this region is critical for the success of global polio eradication. Indonesia, Myanmar, and Thailand appear to have interrupted transmission and joined other regional polio-free countries -- Bhutan, Maldives, and Sri Lanka. Although India has made substantial progress in surveillance, poliovirus types 1 and 3 continue to circulate widely, with focal transmission of type 2. Bangladesh and Nepal are progressing less rapidly, and data from DPR Korea are lacking.

The global decline in polio underscores that existing technology and strategies can eradicate the disease in most countries; however, efforts must be tailored to countries where polio is endemic with large annual birth cohorts and low vaccination coverage in crowded urban areas. These conditions prevail in Bangladesh and India and facilitate the persistence of polio between NIDs. Similar obstacles were encountered in China and Brazil (7,8); however, polio elimination was achieved in these high-risk areas through extra rounds of NIDs and house-to-house, door-to-door, and boat-to-boat vaccination. High-risk areas were identified by the presence of recent polio cases, poor surveillance, low routine vaccination coverage, heavy migration, and crowded living conditions.

Although eradication efforts have been extensive, India accounts for half the world's reported polio cases. Four NIDs have reached greater than or equal to 90% of the population aged less than 5 years. Within the last year, AFP surveillance has reached the target rate, resulting in a more accurate definition of the pattern and intensity of polio transmission. Evidence suggests that many endemic reservoirs of wild poliovirus have been eliminated.

A missed population in India is approximately 13 million children (up to 10% a year) who reside in low coverage, densely populated areas. Better supervised NIDs and house-to-house mopping-up *** vaccination campaigns in areas with persistent transmission are needed to eliminate polio in India by the end of 2000. The Indian government tentatively is planning to conduct two rounds of large-scale mopping-up campaigns during October-November 1999, before the next NIDs during December 1999-January 2000. It is critical that Bangladesh and Nepal synchronize their campaigns with India.

Fewer than 650 days remain to reach the target for global polio eradication. Progress in AFP surveillance and NIDs in the SEAR has led to the apparent elimination of poliovirus in several countries and to substantially reduced circulation in others. **** To eliminate remaining poliovirus reservoirs and meet the 2000 target, accelerated improvement in AFP surveillance and targeted, intensified supplemental vaccination activities will be needed, especially in Bangladesh, India, Nepal, and DPR Korea.

References

1. World Health Assembly. Global eradication of poliomyelitis by the year 2000. Geneva, Switzerland: World Health Organization, 1988; resolution no. (WHA)41.28.

2. Andrus JK, Banerjee K, Hull BP, Smith JC, Mochny I. Polio eradication in the World Health Organization South-East Asia Region by the year 2000: midway assessment of progress and future challenges. J Infect Dis 1997;175(suppl 1):S89-S96.

3. CDC. Update: progress toward poliomyelitis eradication -- South East Asia Region, 1995-1997. MMWR 1997;46:468-73.

4. CDC. Progress toward poliomyelitis eradication -- Bangladesh, 1995-1997. MMWR 1998;47:31-5.

5. CDC. Progress toward poliomyelitis eradication -- India, 1998. MMWR 1998;47:778-81.

6. CDC. Progress toward global eradication of poliomyelitis, 1997. MMWR 1998;47:414-9.

7. Zhang J, Zhang LB, Otten MW Jr, et al. Surveillance for polio eradication in the People's Republic of China. J Infect Dis 1997;175(suppl 1):S122-S134.

8. Andrus, JK, de Quadros CA, Olive JM. The surveillance challenge: final stages of eradication of poliomyelitis in the Americas. In: CDC. Special focus I: public health surveillance and international health 1992. MMWR 1992;41(no. SS-1):21-6.

Bangladesh, Bhutan, Democratic People's Republic (DPR) Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, and Thailand. ** Mass campaigns over a short period (days to weeks) in which two doses of oral poliovirus vaccine are administered to all children, usually aged less than 5 years, regardless of vaccination history, with an interval of 4-6 weeks between doses. *** Focal mass campaigns in high-risk areas over a short period (days to weeks) in which two doses of OPV are administered during house-to-house and boat-to-boat visits to all children aged less than 5 years, regardless of vaccination history, with an interval of 4-6 weeks between doses. **** SEAR polio eradication efforts are supported by its member countries; WHO, United Nations Children's Fund (UNICEF), Rotary International; and donor governments, such as Canada, Denmark, Germany, Japan, Norway, United Kingdom, and the United States (U.S. Agency for International Development {USAID} and CDC).

TABLE 1. Number of reported acute flaccid paralysis (AFP) cases, nonpolio AFP rate,*
confirmed polio cases, and poliovirus strain detected, by country -- South East Asia
Region, 1997-1998
=================================================================================================================================================
                                                                   % AFP cases
                    No. reported              Nonpolio            with adequate                  Confirmed cases&
                      AFP cases              AFP rate               specimens+                    (Wild   virus)
                  ------------------      --------------       ------------------      -------------------------------------      Wild virus
Country           1997         1998       1997      1998        1997         1998             1997                1998            detected@
---------------------------------------------------------------------------------------------------------------------------------------------
Bangladesh         244           470      0.14      0.27          34           49         171       (  5)     266    (    5)        P1/P3
Bhutan               0             2      0.00      0.00           0            0           0       (  0)       2    (    0)         --
DPR Korea            3             0      0.01      0.00           0            0           0       (  0)       0    (    0)         --
India            3,045         9,406      0.22      1.34          34           60       2,278       (706)   3,323    (1,122)       P1/P2/P3
Indonesia          802           779      0.78      1.04          53           78         293       (  0)      91    (    0)         --
Maldives             1             0      0.84      0.00         100            0           0       (  0)       0    (    0)         --
Myanmar            172           181      0.75      0.84          58           69          55       (  0)      31    (    0)         --
Nepal               36            69      0.26      0.36          39           35          12       (  1)      29    (    0)         --
Sri Lanka          115            95      2.12      1.75          45           82           0       (  0)       0    (    0)         --
Thailand           131           271      0.50      1.21          65           79          19       (  1)      25    (    0)         --

Total            4,549        11,273      0.32      1.15          39           61       2,828       (713)   3,767    (1,127)
---------------------------------------------------------------------------------------------------------------------------------------------
* Per 100,000 children aged <15 years. Does not include AFP cases pending classification, which would inflate
  the estimate.
+ Two specimens collected within 14 days of paralysis onset.
& Reported confirmed polio cases based on clinical and virologic findings.
@ Reported wild poliovirus types isolated in 1998.
=================================================================================================================================================

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