Massive outbreak of poliomyelitis caused by type-3 wild poliovirus in Angola in 1999.
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The largest outbreak of poliomyelitis ever recorded in Africa (1093 cases) occurred from 1 March to 28 May 1999 in Luanda, Angola, and in surrounding areas. The outbreak was caused primarily by a type-3 wild poliovirus, although type-1 wild poliovirus was circulating in the outbreak area at the same time. Infected individuals ranged in age from 2 months to 22 years; 788 individuals (72%) were younger than 3 years. Of the 590 individuals whose vaccination status was known, 23% had received no vaccine and 54% had received fewer than three doses of oral poliovirus vaccine (OPV). The major factors that contributed to this outbreak were as follows: massive displacement of unvaccinated persons to urban settings; low routine OPV coverage; inaccessible populations during the previous three national immunization days (NIDs); and inadequate sanitation. This outbreak indicates the urgent need to improve accessibility to all children during NIDs and the dramatic impact that war can have by displacing persons and impeding access to routine immunizations. The period immediately after an outbreak provides an enhanced opportunity to eradicate poliomyelitis. If continuous access in all districts for acute flaccid paralysis surveillance and supplemental immunizations cannot be assured, the current war in Angola may threaten global poliomyelitis eradication. (+info)
Stopping poliovirus vaccination after eradication: issues and challenges.
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Since 1988 reported polio cases worldwide have declined by about 85% and the number of known or suspected polioendemic countries has decreased from over 120 to less than 50. With eradication of poliomyelitis approaching, issues potentially affecting when and how vaccination against poliovirus can be stopped become extremely important. Because of the potential risks and benefits inherent in such a decision, the best available science, a risk-benefit analysis, contingency plans, a stock pile of poliovirus vaccines, and the endorsement by the global policy-making committees will all be needed before vaccination can be discontinued. The scientific basis for stopping polio immunization has been reviewed by WHO. This Round Table article summarizes the current state of knowledge, provides an update on the processes and timelines for certification, containment, and stopping vaccination, and highlights some of the unanswered scientific questions that will be addressed by further research. These include whether transmission of vaccine-derived poliovirus strains could be sustained so that poliomyelitis could re-emerge in a future unvaccinated population and whether prolonged excretion of vaccine-derived poliovirus from individuals with immune deficiencies could be a mechanism through which this could occur. (+info)
Gaps in our knowledge about transmission of vaccine-derived polioviruses.(51/1057)
Progress toward global poliomyelitis eradication, 1999.
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In 1988, the World Health Assembly resolved to eradicate poliomyelitis globally by the end of 2000. Since then, substantial progress has been made in implementing polio eradication strategies, and during 1999 these activities were accelerated to reach the global target. The number of countries where polio is endemic decreased, and the number and quality of vaccination rounds increased. Acute flaccid paralysis (AFP) surveillance improved, and political commitment and the global partnership for polio eradication strengthened. This report updates progress toward achieving the polio eradication goal during 1999. (+info)
Outbreak of poliomyelitis in Angola.
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Between January and June 1999, 1,100 suspected cases of poliomyelitis were reported in Angola. Poliovirus types 3 and 1 were isolated. Patients' ages ranged from 2 months to 14 years. Of the 588 patients whose vaccine status was known, 58 (9.9%) received >4 doses, 216 (36.7%) received 3 or 4 doses, 178 (30.3%) received 1 or 2 doses, and 136 (23.1%) had no history of vaccination. Civil conflict, economic decline, and crowded areas with scarce sanitation and poor water supply are the most important factors implicated in declining rates of routine vaccination, low population immunity, and intense wild poliovirus transmission. The socioeconomic situation and poor roads have created major difficulties for vaccination and surveillance. The Angolan outbreak has serious implications for the global eradication of poliomyelitis. Surveillance of acute flaccid paralysis remains essential in the assessment of strategies for eradication and interventions to interrupt wild poliovirus transmission. (+info)
Human monoclonal antibodies reactive to oligodendrocytes promote remyelination in a model of multiple sclerosis.
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Promoting remyelination, a major goal of an effective treatment for demyelinating diseases, has the potential to protect vulnerable axons, increase conduction velocity, and improve neurologic deficits. Strategies to promote remyelination have focused on transplanting oligodendrocytes (OLs) or recruiting endogenous myelinating cells with trophic factors. Ig-based therapies, routinely used to treat a variety of neurological and autoimmune diseases, underlie our approach to enhance remyelination. We isolated two human mAbs directed against OL surface antigens that promoted significant remyelination in a virus-mediated model of multiple sclerosis. Four additional OL-binding human mAbs did not promote remyelination. Both human mAbs were as effective as human i.v. Ig, a treatment shown to have efficacy in multiple sclerosis, and bound to the surface of human OLs suggesting a direct effect of the mAbs on the cells responsible for myelination. Alternatively, targeting human mAbs to areas of central nervous system (CNS) pathology may facilitate the opsonization of myelin debris, allowing repair to proceed. Human mAbs were isolated from the sera of individuals with a form of monoclonal gammopathy. These individuals carry a high level of monoclonal protein in their blood without detriment, lending support to the belief that administration of these mAbs as a therapy would be safe. Our results are (i) consistent with the hypothesis that CNS-reactive mAbs, part of the normal Ig repertoire in humans, may help repair and protect the CNS from pathogenic immune injury, and (ii) further challenge the premise that Abs that bind OLs are necessarily pathogenic. (+info)
In 1988, the World Health Assembly resolved to eradicate poliomyelitis globally by 2000 (1). The African Region (AFR) of the World Health Organization (WHO) began implementing polio eradication strategies in 1996, including National Immunization Days (NIDs*) and acute flaccid paralysis (AFP) surveillance (2,3). This report summarizes progress toward polio eradication in AFR during 1999-March 2000, and suggests that although substantial progress has been reported toward interrupting poliovirus transmission in eastern and southern Africa, poliovirus remains endemic in other African countries in west and central Africa, especially among those experiencing internal strife or civil war. (+info)
The relation between acute persisting spinal paralysis and poliomyelitis vaccine (oral): results of a WHO enquiry.
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The present report presents the findings in 8 countries at the end of the first 5 years of an international investigation into the possible relationship between acute persisting spinal paralysis and the use of oral poliomyelitis vaccine.The most striking finding was the high association with type 3 virus in the recipient cases and with type 2 virus in the "contacts" and "possible contacts". Most of the cases in the recipient groups occurred in children under 5 years of age in all countries, but in the "contact" groups in the countries in which vaccination is offered through the year, many of the cases occurred in the non-immune parents of recently vaccinated infants.There were marked differences among countries, and it was not possible to pinpoint a single factor as the sole cause. However, the quality of the vaccine clearly played an important role. For some time, and certainly at the beginning of this enquiry, some of the countries were using vaccine from the same source without continuous external control and were using seed viruses at high passage levels. The situation changed during the enquiry and the incidence of paralytic cases decreased. The enquiry will be continued and particular efforts will be made to establish the cause of the associated paralysis. The findings of the enquiry confirm that oral Sabin poliomyelitis vaccines are among the safest vaccines in use today. (+info)