In May 1988, the 41st World Health Assembly committed the Member States of the World Health Organization (WHO) to the global eradication of poliomyelitis by the year 2000 (resolution WHA41.28). The resolution specified that the polio eradication initiative should be pursued in ways that would strengthen the Expanded Programme on Immunization (EPI). In 1989, the 42nd World Health Assembly approved a general Plan of Action for Global Polio Eradication.
The global effort to eradicate polio is the largest public health initiative in history. Since the initiative was launched in 1988 extraordinary progress has been made to halt transmission of wild poliovirus and achieve global certification of eradication by 2005. In 1988, polio existed in over 125 countries on five continents, and more than 350 000 children were paralyzed that year. By the end of 2002, the number of polio-infected countries has decreased to seven (Figure 1.1), polio has been eliminated from three continents, and reported poliomyelitis cases has fallen to around 1900. Poliomyelitis transmission has been interrupted in the American, European, and Western Pacific Regions, and by end 2002 more than 180 countries and territories were polio-free. With the eradication of polio and the eventual cessation of polio immunization, the world will save US$ 1.5 billion per year.
Current eradication strategies recommended by WHO have proved successful; these four strategies are:
· high, routine infant immunization coverage with at least three doses of oral polio vaccine (OPV) plus a dose at birth in polio-endemic countries;
· national immunization days (NIDs) targeting all children <5 years;
· acute flaccid paralysis (AFP) surveillance and laboratory investigations; and
· mop-up immunization campaigns to interrupt final chains of transmission.
The laboratory has a crucial role in ensuring that the initiative meets its objectives. Since agents other than polioviruses can cause acute flaccid paralysis, all suspect cases must undergo thorough virological investigation. Most poliovirus infections are asymptomatic, with clinical symptoms being observed in only 0.1 to 1% of infections. For this reason it is essential that stool specimens from every identified AFP case be subjected to thorough and systematic examination for the presence of wild poliovirus — missing virus in one case may mean that a thousand infections have been missed.
Figure 1.1: Progress in polio eradication 1988–2002
For the eradication initiative to be effective it is essential to achieve close integration between surveillance and laboratory activities to ensure that the data generated from epidemiology and virology are available as the basis for action by immunization programme managers and others responsible for implementing eradication strategies. EPI managers, clinicians, epidemiologists and virologists must work together as a team. The establishment and smooth functioning of these teams form an integral part of the overall polio eradication effort and provide a basis for strengthening EPI and related health unit efforts in other disease areas requiring laboratory support.
In 1989 a Plan of Action was formulated detailing laboratory support for global eradication of poliomyelitis. It described the activities needed to establish a three-tiered global network of laboratories, each with well-defined responsibilities. Considerable progress has been made. At all three levels of the network, and in all six WHO regions, Global Specialized, Regional Reference and National Laboratories are working together in the largest coordinated public health laboratory network ever.
In the initial stages of the establishment of this network, standardized methods were set out in a Manual for the Virological Investigation of Poliomyelitis (WHO/EPI.CDS/POLIO/90.1). The manual was distributed to potential network laboratories and formed the basis for training at WHO-sponsored courses and during individual training attachments to reference laboratories. In response to changing requirements and lessons learned in establishing and developing the Global Polio Laboratory Network, the manual was revised in 1997 (WHO/EPI/GEN/97.01) and in 2001 (electronic distribution only).
In May 1999, the World Health Assembly reaffirmed the commitment of WHO to the eradication of poliomyelitis and urged all Member States to begin the process leading to the laboratory containment of wild poliovirus. The purpose of containment is to prevent wild poliovirus transmission from the laboratory to the increasingly non-immune community. In December 1999, WHO published the WHO global action plan for laboratory containment of wild polioviruses (GAP) (WHO/V&B/99.32) in preparation for global certification of eradication in 2005 and the eventual decline or cessation of global poliovirus immunization five to ten years later. The document is under revision and the second edition to be published in 2004 will incorporate lessons learned from biomedical laboratory surveys and inventories implemented in more than a hundred nations in five of the six WHO regions (WHO/V&B/03.11).
The revised GAP (GAP II) describes two phases of activities that are linked to the major eradication objectives.
The Laboratory Survey and Inventory phase covers the period when wild poliovirus continues to circulate. During this phase, nations will survey all biomedical laboratories to identify those with wild poliovirus infectious or potential infectious materials and encourage destruction of all unneeded materials. Nations will develop an inventory of laboratories that retain wild poliovirus and potential infectious materials and instruct laboratories on the inventory to institute enhanced biosafety level-2 (BSL-2/polio) measures for safe handling of materials. Nations will begin planning for Global Certification.
The Global Certification phase begins one year after detection of the last wild poliovirus anywhere in the world, at which time the probability is high that all human transmission will have ceased. In this phase nations will notify biomedical laboratories that wild poliovirus transmission has been interrupted. Additionally all laboratories on the national inventory will be contacted and instructed to select one or more of the following three options for containment: render materials non-infectious for poliovirus, or destroy them, under appropriate conditions; implement biosafety requirements appropriate for the laboratory activities being performed, i.e. BSL-2/polio or BSL-3/polio depending on whether polio replication procedures are to be performed; or transfer wild poliovirus infectious and potential infectious materials to laboratories capable of meeting the required biosafety standards where essential work can be continued. Nations must complete containment activities one year after notification of eradication and will document completion of all containment requirements for global certification of polio eradication.
GAP II states that post-Global Certification biosafety requirements will depend on decisions made about discontinuing universal polio immunization. If polio immunization is discontinued containment requirements for wild as well as oral polio vaccine (OPV) viruses are likely to become more stringent than those outlined above.