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Letter
Wild Poliovirus Type 1, Central
African Republic
Ionela Gouandjika-Vasilache,*
Jean Kipela,† Regis Mbay Daba,‡ Vicroire Mokwapi,† Emmanuel Nambozuina,‡
Joseph Cabore,§ Omer Pasi,¶ and Didier Menard*
*Institut Pasteur de Bangui, Bangui, Central African Republic; †World
Health Organization, Bangui, Central African Republic; ‡Ministry of Health,
Bangui, Central African Republic; §World Health Organization, Yaounde,
Cameroon; and ¶Centers for Disease Control and Prevention, Atlanta, Georgia,
USA
Suggested
citation for this article
To the Editor: In this article we summarize the investigation
and response to the reemergence of wild poliovirus (WPV) type 1 in the
Central African Republic (CAR) in 2003. Since 2000, reported annual routine
vaccination coverage with >3 doses of oral polio vaccine (OPV) has
been very low in CAR (<50%); National Immunization Days have been conducted
every year since 1996, except in 2002 (1).
From December 2003 to November 2004, the active acute flaccid paralysis
surveillance system reported 112 cases of acute flaccid paralysis suspected
to be poliomyelitis and 4 deaths (case-fatality ratio 4%). Fecal samples
were collected and sent to the Institut Pasteur de Bangui. WPV type 1
(WPV1) was isolated in 30 cases (27%), vaccine polioviruses in 15 cases
(5 type 1, 5 type 2, and 6 type 3) (13%), and nonpolio enteroviruses in
18 cases (16%). Epidemiologic investigations showed that 97% of patients
with poliomyelitis received <3 doses of OPV and 93% of patients were
<5 years of age. Isolates were sent to the National Institute for Virology
in Johannesburg, South Africa, for sequencing. All viruses were type 1
and could be traced to common ancestral strains that circulate in disease-endemic
reservoirs shared by northern Nigeria and southern Niger (WEAF-B genotype).
The first importation occurred in Chad in August 2003 from northeastern
Nigeria, and the outbreak spread to the adjacent countries of Cameroon
in October 2003 and the CAR in December 2003.
In CAR, the first case occurred in a 19-month-old child living in Ndjoh
village north of Bossembélé in Ombela M'Poko. A special mission by the
World Health Organization/CAR officer determined that the child had not
received OPV and had traveled 200 km into a northern region a few weeks
before the onset date of December 16, 2003. The last case of acute flaccid
paralysis in this region was noted on November 23, 1999. Supplemental
immunization activities were conducted from March to April 2004. However,
collected funds were not enough to cover the entire country, and only
sanitary regions 1, 3, 4, 5, and 7 were included. The OPV coverage rate
was estimated at 104% for the first round and 141% for the second round
(CAR Ministry of Health, unpub. data). The second case occurred in April
2004 in Gadzi in sanitary region 2 in a 6-year-old nomad child who had
not received OPV. The third case occurred in May 2004, in a village near
where the second case was diagnosed, in a 23-month-old child who had not
received OPV. Twenty-five other cases occurred between July and November
in sanitary region 2 (Figure).
This outbreak is the largest epidemic of WPV1 in CAR since July 2000,
when the last case of WPV1 was isolated (2). Probable
reestablishment of endemic poliovirus and possible diffusion of WPV1 to
countries further south, such as the Democratic Republic of Congo, is
a concern. Four main reasons may explain this outbreak: 1) the close links
with countries, such as Chad and Cameroon, where WPV1 recently reemerged;
2) declining rates of routine vaccination and low population immunity
after disruption of health service infrastructures and road networks;
3) displaced persons' living in crowded areas with little sanitation and
poor water supply; and 4) lack of response preparedness to WPV importation.
Epidemiologic investigation of the first case was not conducted until
>1 month after onset and implementation of the polio immunization initiative
in a limited area.
In May 2004, a decision was made by African Union health ministers to
conduct a series of synchronized poliovirus campaigns across the African
continent. Four rounds of National Immunization Days were conducted in
CAR from August to December 2004. The OPV coverage rate in 600,000 children
<5 years of age was estimated to be 89% in August, 98% in September,
102% in November, and 100% in December. Since November 2004, only 1 WPV1
case has been virologically confirmed in sanitary region 2. WPV1 has not
been isolated in 2005.
To restore the gains made in polio eradication in Central Africa, WPV
transmission must be interrupted in Nigeria and Niger (3).
Until then, neighboring countries must implement high routine vaccination
coverage and high-quality, supplemental immunization activities. In 2002,
these steps successfully prevented importation of WPV into Bangladesh
and Nepal during a resurgence of polio in India. Surveillance standards
must also be maintained to ensure the rapid detection of any WPV importation,
thus allowing timely response and containment.
Acknowledgments
We thank Jean Fandema
and Arthur Mazitchi for virus identification and intratypic differentiation
during this epidemic and Antoine Talarmin for useful discussions on
the manuscript. This work was conducted with the help of WHO/AFRO and
WHO/Headquarters grants.
References
- Ministère de la Santé et de la Population de la République
Centrafricaine. National Certification Committee. Annual report, 2003.
- Menard D, Gouandjika I, Mberio-Yaah F, Mokwapi F, Soro B, Djalai MI,
et al. Results
of active surveillance of acute flaccid paralysis in the Central African
Republic and Chad from 1995 to 2000. Med Trop (Mars). 2002;62:63–9.
- Centers for Disease Control and Prevention. Progress
toward global poliomyelitis eradication, Nigeria, January 2003–March
2004. MMWR Morb Mortal Wkly Rep. 2004;53:343–6.
Suggested citation
for this article:
Gouandjika-Vasilache
I, Kipela J, Mbay Daba R, Mokwapi V, Nambozuina E, Cabore J, et al. Wild
poliovirus type 1, Central African Republic [letter]. Emerg Infect Dis
[serial on the Internet]. 2005 Sep [date cited]. Available from
http://www.cdc.gov/ncidod/EID/vol11no09/05-0517.htm
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