Poliomyelitis eradication: progress, challenges for the end game, and preparation for the post-eradication era.

In 1988, the World Health Assembly resolved to eradicate poliomyelitis globally by the year 2000. Dramatic progress toward this goal has occurred: three of the six WHO regions (Region of the Americas, European Region, and Western Pacific Region) are now polio free; and the number of polio-endemic countries decreased from over 125 in 1988 to 30 in 1999. Intensified efforts currently are underway to reach the target as soon as possible after 2000 in the three remaining polio-endemic WHO regions (African Region, Eastern Mediterranean Region, and South-East Asia Region). Even in polio-endemic regions, many countries are already polio free as the geographic extent of poliovirus shrinks while others. especially those experiencing conflict and war, pose substantial challenges to implementing the proven polio eradication strategies. Increasing attention and research now are devoted to the certification of polio eradication in the polio-free regions (that will include the first phase of implementing the Global Plan of Action for the laboratory containment of wild poliovirus) and formulating a policy for stopping all polio vaccination once eradication, containment, and global certification have been achieved. This report outlines the progress toward polio eradication and highlights some of the remaining issues and challenges that must be addressed before polio becomes a disease that future generations know only by history.

Eradication of poliomyelitis in countries affected by conflict.

The global initiative to eradicate poliomyelitis is focusing on a small number of countries in Africa (Angola, Democratic Republic of the Congo, Liberia, Sierra Leone, Somalia, Sudan) and Asia (Afghanistan, Tajikistan), where progress has been hindered by armed conflict. In these countries the disintegration of health systems and difficulties of access are major obstacles to the immunization and surveillance strategies necessary for polio eradication. In such circumstances, eradication requires special endeavours, such as the negotiation of ceasefires and truces and the winning of increased direct involvement by communities. Transmission of poliovirus was interrupted during conflicts in Cambodia, Colombia, El Salvador, Peru, the Philippines, and Sri Lanka. Efforts to achieve eradication in areas of conflict have led to extra health benefits: equity in access to immunization, brought about because every child has to be reached; the revitalization and strengthening of routine immunization services through additional externally provided resources; and the establishment of disease surveillance systems. The goal of polio eradication by the end of 2000 remains attainable if supplementary immunization and surveillance can be accelerated in countries affected by conflict.

Progress towards the eradication of poliomyelitis globally and in Africa, January 2000.

Led by an international partnership including Rotary International, the WHO, UNICEF and the Centers for Disease Control and Prevention in the USA, the global initiative to eradicate poliomyelitis has made remarkable progress since its beginning in 1988. The number of polio cases has decreased from an estimated 350,000 cases in 1988 to just over 5,000 reported cases in 1999. Following successful eradication from the WHO Region of the America's, certified as polio-free in 1994, wild poliovirus was last reported from the Western Pacific Region (including China) in 1997, and from the European Region (including all countries of the former Soviet Union) in November 1998. Large parts of Southern and Northern Africa and the Middle East are also polio-free. This success is related to the implementation of annual nationwide supplemental oral poliovaccine (OPV) campaigns in all recently or currently polio-endemic countries, targeting all children under 5 years with two doses of OPV. Progress of the initiative is monitored by special surveillance systems for all cases of acute flaccid paralysis (AFP) in children under 15 years, including virological testing to rule out wild poliovirus infection. The initiative currently focuses on a limited number of remaining endemic countries in South Asia and Africa, including India, Pakistan, Bangladesh, and Nigeria. The initiative is also beginning to be successful in several countries affected by conflict situations, such as Afghanistan, Sudan (South), Somalia, Democratic Republic of the Congo and Angola.

Poliomyelitis eradication in the Western Pacific Region.

Polio eradication activities in the Western Pacific Region (WPR) have reduced the transmission of wild poliovirus to one remaining focus of endemic transmission in the Mekong Delta area of South Vietnam and Cambodia. There has been a high level of government commitment for national immunization days in all WPR countries in which poliomyelitis was previously endemic and for continuous improvement in acute flaccid paralysis (AFP) surveillance quality. The total number of reported confirmed poliomyelitis cases in 1995 (as of June 1996) was 432, only 7% of the total of 5825 cases reported in 1990. In 1995, wild poliovirus was isolated from only 19 of 4800 AFP patients from whom specimens were collected and analyzed. There has been one importation of wild poliovirus type 1 into China from a neighboring country. An international Regional Commission for the Certification of Poliomyelitis Eradication in the WPR has been formed and met for the first time in April 1996.

Development and coordination of the Polio Laboratory Network in the Western Pacific Region of the World Health Organization.

A multitiered network of polio laboratories, consisting of specialized reference laboratories, regional reference laboratories, national laboratories and, in the case of China, provincial laboratories, was established in the Western Pacific Region of the World Health Organization (WHO) in 1992. The network currently consists of 43 laboratories within the Region and is coordinated through the WHO Regional Office in Manila. As the levels and extent of supplementary immunization and acute flaccid paralysis surveillance activities have increased, so has the work load of network laboratories. The total number of stool specimens collected and processed in Polio Laboratory Network laboratories in this WHO region in 1995 exceeded 15,000. With the Region now establishing the criteria necessary for certification of polio-free status, it is essential for the Polio Laboratory Network to establish international confidence in its ability to carry out its role in the eradication of polio.

The experience of countries in the Western Pacific Region in conducting national immunization days for poliomyelitis eradication.

Experience with national immunization days (NIDs) in six countries of the Western Pacific Region has shown that political support at all levels, detailed logistics plans, strategies appropriate to the local situation, and simple social mobilization messages have been key factors in the success of NIDs. Conventional strategies that may apply to conducting routine Expanded Programme on Immunization vaccinations do not necessarily apply to NIDs, in which the maximum number of children must be immunized in 1 or 2 days. Setting up temporary immunization posts at sites convenient to the local situation, moving the posts once or twice during the course of a day, and using volunteers to staff them are among many of the adaptations used successfully. Coverage figures published immediately after an NID can be misleading because of uncertainty about the true denominator. The true measure of the success of NIDs is in surveillance for wild poliovirus after the event.

Strengthening routine immunization services in the Western Pacific through the eradication of poliomyelitis.

Infant immunization coverage in the Western Pacific Region of the World Health Organization was reviewed to evaluate the impact of polio eradication activities on routine immunization services. The trend in bacille Calmette-Guérin (one dose; BCG), diphtheria-tetanus toxoids-pertussis (three doses; DTP3), and measles (one dose) vaccination rates was analyzed from the beginning of eradication activities in 1990 to 1994 in the five polio-endemic countries that conducted supplementary oral polio vaccine immunization. In China and the Philippines, coverage for each antigen remained at or above 90% and 85%, respectively, while in Vietnam, coverage for all three antigens rose from 85% to 95%. BCG, DTP3, and measles vaccine coverage more than doubled in the People's Democratic Republic of Lao and increased by >30% in the Kingdom of Cambodia during the same period.

Poliomyelitis eradication and its impact on primary health care in the Philippines.

Since 1992, the Philippines has conducted four national immunization days (NIDs) for polio eradication. Surveillance for acute flaccid paralysis (AFP) began in 1992. Through good routine immunization, the incidence of paralytic polio had decreased to low levels in the Philippines even before the NIDs were initiated. With continuously improving AFP and virologic surveillance, wild poliovirus has not been isolated since May 1993. NIDs had a direct positive effect on child health through supplementary immunization with oral poliovirus vaccine, measles vaccine, and tetanus toxoid, as well as through the distribution of vitamin A. Following the successful NIDs, the government budget for vaccine purchases increased significantly. Also, the NID strategy was used as a model for several other priority prevention programs of the Department of Health. Through the development of AFP surveillance, polio eradication also helped to improve surveillance for other Expanded Programme on Immunization diseases.

Current status of the global eradication of poliomyelitis.

Substantial progress towards the global eradication of poliomyelitis by the year 2000 has been achieved since May 1988 when WHO Member States adopted this goal at the Forty-first World Health Assembly. Virtually all polio-endemic countries have begun to implement the WHO-recommended strategies to eradicate polio and it is expected that, by the end of 1997, all endemic countries in the world will have conducted full National Immunization Days (NID), providing supplemental oral polio vaccine (OPV) to nearly two-thirds of all children < 5 years. In contrast, although globally acute flaccid paralysis (AFP) surveillance was being conducted in 126 (86%) of 146 countries where polio is or recently was endemic, surveillance remains incomplete and untimely. A global network of polio laboratories, capable of detecting wild poliovirus when and where it occurs, has been developed. Furthermore, in countries where polio virus circulation has been limited to focal areas, and surveillance is adequate, mopping-up campaigns are being conducted to eliminate the final chains of transmission. The process for certification of polio eradication has been established in each WHO region as well as at the global level. The impact of the eradication initiative is evident, with an 88% decrease in the number of reported cases globally since 1988. In order to achieve the goal of eradication, the rapid development of complete and timely AFP surveillance and the continuation of effective NIDs constitute an urgent priority. This is of particular relevance in the remaining polio-endemic countries, especially in those that are affected by war or politically isolated and are important remaining reservoirs from where wild poliovirus continues to spread into bordering or even distant polio-free countries. External support will continue to be required by those countries and regions where the incidence of polio has reached low levels to ensure that final chains of poliovirus transmission are interrupted and to permit the eventual certification of eradication. The year 2000 objective for achieving poliomyelitis eradication remains a feasible target.

An outbreak of a food-related illness resembling boric acid poisoning.

An outbreak of an illness suggestive of boric acid poisoning occurred among 51 persons who had eaten lunch at the cafeteria of the United States Agency for International Development in Islamabad, Pakistan, on February 11, 1990. Affected patients had headache and severe myalgias 2 to 4 hours after eating lunch. Fever, nausea and vomiting, red eyes, and photophobia were also reported. Among 25 patients (49%), a sunburn-like inflammation of the skin of the face developed, which subsequently desquamated. One patient required hospitalization for 1 day because of dehydration. Among all patients, the only symptoms remaining 72 hours after the meal were mild headache, fatigue, and peeling skin. Those persons who became ill were more likely to have eaten one particular food item (minestrone soup) for lunch than were those who did not become ill. A similar illness has been described following ingestion of boric acid. However, the results of an analysis of serum samples collected 3 days after the lunch from 24 patients did not show boron above normal background levels. Because of boron's short half-life, however, these data do not rule out the possibility that patients may have had higher boron levels at the onset of the illness.

An outbreak of cryptosporidiosis in a day-care center in Georgia.

Diarrhea among the 11 million children attending day-care centers in the United States is common, but infection control of enteric pathogens in the day-care center setting remains a challenge. In August 1989, an outbreak of cryptosporidiosis was investigated at a day-care center in Georgia. A total of 49% (39/79) of children and 13% (3/23) of staff members who submitted stool specimens were found to be infected with Cryptosporidium. A total of 77% (30/39) of infected children had mild-to-moderate diarrhea (median duration, 5 days). Children were at highest risk if they were less than age 36 months, in diapers, and not toilet trained. Serial stool specimens were collected from 12 infected children. After diarrhea had ceased, oocyst shedding continued in all children for a mean duration of 16.5 days. It is concluded that the prevalence of asymptomatic infections and the duration of shedding after the end of symptoms may previously have been underestimated. Cohorting or exclusion from the day-care center of children who are asymptomatic shedders is not practical, and the management of cryptosporidiosis in day-care centers remains a major challenge.

Comparing cause-specific infant mortality in a West German state and the United States of America.

The infant mortality rate in North Rhine Westphalia (NRW), the most populous West German state, has continuously been around 10% higher than the German national average in the post-war period. Using white singleton data from the US 1980 National Infant Mortality Surveillance project (NIMS) and similar 1980/1981 data from NRW we compared infant mortality by birthweight and cause to describe the distribution of excess mortality in NRW. The US infant mortality rate was 8.7 deaths per 1,000 live births, compared with 13.1/1,000 for NRW (rate difference: 4.3/1,000). Of the 4.3/1,000 overall rate difference, 1.9/1,000 was attributable to neonatal deaths, 2.4/1,000 to postneonatal deaths. A major proportion, 2.0/1,000, of the overall rate difference of 4.3/1,000 was attributable to normal birthweight deaths postneonatally. 0.85/1,000 of this 2.0/1,000 rate difference was attributable to SIDS, 0.44/1,000 to external causes and 0.42/1,000 to infections.