1 figure, 1 table omitted
Since the 1988 World Health Assembly resolution to eradicate poliomyelitis
globally1 through 2002, the number of countries
where polio is endemic declined from 125 to seven, and the estimated incidence
of polio decreased >99%.2 In 2002, the European
Region became the third World Health Organization (WHO) region certified as
polio-free, joining the Region of the Americas and the Western Pacific Region,
certified polio-free in 1994 and 2000, respectively.3- 5 Despite
these achievements, a provisional total of 1,920 polio cases were reported
during 2002, a substantial increase from 483 in 2001, reflecting primarily
the large polio epidemic in India.6 This
report summarizes global progress achieved in polio eradication during 2002
and describes remaining challenges.
Coverage among infants with 3 doses of oral poliovirus vaccine (OPV3)
in 2001 was estimated at 75% globally, a decrease from 82% in 2000.* Coverage
varied among WHO regions, from 54% in the African Region to 95% in the European
Region. Except for Egypt, reported routine vaccination coverage in 2002 continues
to be low in the remaining countries where polio is endemic.
All countries where polio is endemic and many countries where polio
was recently endemic conducted supplemental immunization activities (SIAs)
during 2002. An estimated 500 million children were vaccinated during 266
rounds of National Immunization Days (NIDs),† sub-NIDs (SNIDs),‡
or mopping-up activities. All countries used house-to-house vaccination in
part or all of the SIA target areas. SIA monitoring data confirmed low vaccination
coverage for some SIAs, particularly in Uttar Pradesh (India) and northern
Nigeria, where poliovirus transmission remained intense.
All WHO regions have achieved certification-standard acute flaccid paralysis
(AFP) surveillance consisting of (1) an annual nonpolio AFP detection rate
of ≥1 per 100,000 persons aged <15 years and (2) at least two adequate
stool specimens§ collected from ≥80% of persons with AFP. The African
Region reached certification-standard AFP surveillance quality for the first
time in 2002, with a nonpolio AFP detection rate of 3.1 and adequate specimens
collected from 81% of persons with AFP. Globally, the nonpolio AFP rate increased
from 1.6 in 2001 to 1.9 in 2002. The proportion of persons with AFP from whom
adequate stool specimens were collected increased from 82% in 2001 to 87%
in 2002. Except for Somalia (adequate specimens from 67% of persons with AFP),
all other countries where polio is endemic achieved certification-standard
AFP surveillance in 2002.
In 2002, a total of 97% of the 145 poliovirus laboratories in the global
network were formally accredited by WHO. Global network laboratories tested
approximately 70,000 fecal samples, a 12% increase over 2001. Despite a fourfold
increase in the isolation of wild virus from 2001 to 2002, timeliness of reporting
of laboratory results improved. Primary isolation results were available within
28 days of receipt in the national laboratory for 90% of samples, and intratypic
differentiation was available within 28 days of isolate receipt in the regional
reference laboratory for 88% of isolates.
The number of countries where polio is endemic decreased from 10 in
2001 to seven in 2002. Of the 1,920 polio cases reported in 2002, a total
of 1,893 (99%) were reported from three countries: India (1,599), Nigeria
(201), and Pakistan (93). Despite certification-standard surveillance, few
cases were reported in Afghanistan (11), Egypt (seven), Niger (three), and
Somalia (three). Virus importations were detected in Zambia (two cases) and
Burkina Faso (one case). Recently endemic poliovirus reservoir (Ethiopia,
Angola, and Sudan) reported no cases in 2002 in the presence of sensitive
A substantial increase in polio occurred in India, from 268 cases reported
in 2001 to 1,599 cases in 2002, representing >83% of the globally reported
cases in 2002. The states of Uttar Pradesh and Bihar accounted for 1,241 (78%)
and 121 (8%) of the total cases in India, respectively. During 2001-2002,
the number of genetic lineages of wild poliovirus circulating in India remained
the same for wild poliovirus type 1 (P1) (three major lineages) and wild poliovirus
type 3 (P3) (four major lineages). Analysis of genetic data demonstrated that
all lineages identified in India in 2002 were derived from strains that circulated
in Utter Pradesh during 2000-2001.
In Nigeria, the increased number of reported wild poliovirus cases was
in part caused by improved AFP surveillance. Despite the increase, poliovirus
circulation was restricted geographically, with seven states in northern Nigeria
reporting >80% of cases; southern Nigeria remained largely poliovirus-free.
Pakistan reported 22% fewer cases in 2002 (93) compared with 2001 (119). In
addition, transmission was more focal in 2002 compared with 2001. Genetically
related P3 clusters decreased from six in 2001 to one in 2002.
Egypt continued to report P1 in 2002. Since 2000, environmental surveillance
has detected evidence of widespread P1 transmission in Upper and Lower Egypt,
compared with AFP surveillance, which detected few poliovirus-confirmed cases.
During the second half of 2002, seven cases of polio were detected from Upper
and Lower Egypt, including the greater Cairo area.
In Somalia, the last polio case was reported in October 2002 and was
caused by P3. Only eleven poliovirus-confirmed cases were reported in 2002
in Afghanistan, despite the recent war and return of approximately 2 million
refugees. Genetic sequencing data indicate that the only remaining area of
endemic transmission in Afghanistan is in the south, near Kandahar. Low-intensity
poliovirus transmission continued in Niger in 2002. Although polioviruses
detected are related closely to Nigerian polioviruses, evidence exists of
independent low-level wild poliovirus transmission in southern Niger. Vaccination
campaigns were conducted in response to virus importations into Burkina Faso
and Zambia with no subsequent spread.
Following episodes of circulating vaccine-derived poliovirus (cVDPV)
type 1 in Haiti, the Dominican Republic (2000-2001), and the Philippines (2001),
another outbreak (four cases) of cVDPV type 2 was detected during March-April
2002 in Madagascar, a country where OPV3 coverage in 2000 was 34%.7,8 No additional cases were detected
in Madagascar after NIDs were conducted in mid-2002. The global polio laboratory
network continues to screen for cVDPV isolates. Regional reference laboratories
immediately refer suspected isolates to specialized laboratories for genetic
sequencing studies. Since 2000, approximately 3,400 Sabin viruses from AFP
cases have been screened without finding additional cVDPVs.
Progress has been made toward laboratory containment of wild polioviruses.9 Of 207 countries and territories where polio is
not endemic, 155 (75%) have established a national task force and a national
plan of action for laboratory containment. By the end of 2002, a total of
149 WHO member states had initiated national laboratory surveys. Of those,
79 countries had completed and submitted an inventory of facilities holding
wild-type polioviruses and potentially infectious materials, including 41
of 51 European, 33 of 36 Western Pacific, and five of 23 Eastern Mediterranean
countries. Laboratory surveys are ongoing in 19 of 48 countries in the Region
of the Americas, including the United States.
As part of post-eradication polio vaccination policy development, a
framework was created for assessing and managing the risks for polio in the
post-eradication era and addresses risks associated with (1) polio from continued
use of OPV (i.e., vaccine-associated paralytic polio), (2) cVDPV or vaccine-derived
poliovirus associated with immunodeficiency, and (3) the handling of wild
poliovirus stocks. The framework summarizes knowledge on the magnitude of
these risks and their expected evolution over time.
Vaccines and Biologicals Dept, World Health Organization, Geneva, Switzerland.
Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases;
Global Immunization Div, National Immunization Program, CDC.
Progress toward global polio eradication in 2002 included the certification
of eradication in 51 countries of the European Region, a decrease from 10
remaining countries in 2001 to seven countries in 2002, and continued absence
of indigenous wild poliovirus type 2, last detected in October 1999.10 Approximately 3 billion persons now live in 134
countries, areas, and territories certified free of indigenous wild poliovirus.
Further progress was evident in the reduction in diversity of poliovirus
lineages in the majority of countries, and polio-free status was sustained
in recently endemic, challenging country settings such as Bangladesh, the
Democratic Republic of Congo, Ethiopia, and Sudan. In Angola, the April 2002
cease fire resulted in vaccinators having access to children in areas that
had been inaccessible for years. Access to children also improved in Somalia
in 2002. In addition, Afghanistan has recovered from a disruption in AFP surveillance
activities following the September 11, 2001, terrorist attacks in the United
Despite these achievements, the fourfold increase in polio incidence
globally, focused in India and northern Nigeria, represents a critical challenge
to the program. Efforts are being focused on the northern Indian states of
Uttar Pradesh and Bihar because of the intensity of transmission, and genetic
evidence that these states were the source for re-introduction of poliovirus
into other states that had become polio-free. Key factors contributing to
the epidemic include the decline in the number, extent, and quality of SIAs
during 2001-2002 in areas where large birth cohorts, population density, hygiene,
and climate favored poliovirus transmission. Six large-scale SIAs will be
conducted in India in 2003 (two NIDs and four SNIDs), and two NIDs are planned
for early 2004. Afghanistan, Egypt, Niger, Nigeria, Pakistan, and Somalia
also will conduct multiple additional rounds of large-scale SIAs during 2003-2004.
The global funding gap for polio eradication is another challenge to
the program. This financial shortfall for 2003-2005, resulting largely from
the recent global economic slowdown, has resulted in a lack of resources available
for SIAs in countries where polio was recently but not currently endemic and
that remain at high risk for re-emergence of polio. To ensure activities will
proceed for the second half of 2003, the polio partnership has appealed to
donors to have funds in place before mid-2003.
Progress achieved in laboratory containment is encouraging, and planning
for the post-eradication era has included ongoing evaluation of the scientific,
economic, political, operational, and financial implications of policy options.
An April 2002 meeting of public health leaders (primarily from developing
countries) in Annecy, France, generated advice on the development of postcertification
policies. A communications and public information plan will keep countries
and interested parties abreast of the issues. The international community
should make every effort to overcome remaining challenges and achieve a polio-free
*This decrease is primarily the result of a change in the methodology
used to produce official national estimates in two countries (India and China).
†Nationwide mass campaigns during a short period (days to weeks)
in which 2 doses of OPV are administered to all children (usually aged <5
years), regardless of previous vaccination history, with an interval of 4-6
weeks between doses.
‡Campaigns similar to NIDs but confined to parts of the country.
§Two specimens collected at an interval of at least 24 hours, within
14 days of paralysis onset, and adequately shipped to the laboratory.
Progress Toward Global Eradication of Poliomyelitis, 2002. JAMA. 2003;290(2):188-190. doi:10.1001/jama.290.2.188