ARCHIVED - Tenth informal consultation on the global polio laboratory network, 6-8 September 2004

Background

A global network of virology laboratories was established by WHO in 1988 to support the Polio eradication initiative. Representatives of reference laboratories serving the remaining polio-endemic regions and of seven global specialized laboratories met at WHO headquarters in Geneva, Switzerland, on 6 - 8 September 2004 to review the network's activities and performance, to discuss issues related to the development of oral poliovirus (OPV) cessation policies and to make recommendations for further improvements. The laboratory network is a key component of a surveillance system that investigates cases of acute flaccid paralysis (AFP) for excretion of polioviruses. Sensitive surveillance is indicated by the ability to detect annually at least one AFP case per 100 000 persons aged under 15 years, by the collection of adequate*stool samples from each case and by the analysis of samples in a WHO-accredited laboratory.

Conclusions and recommendations

Conclusions

To halt the last remaining transmission chains, laboratory information is key to identifying remaining foci of wild polioviruses to target supplementary immunization activities. The laboratory network detected six circulating genotypes of polioviruses (type 1 genotypes NEAF, SOAS and WEAF-B, and type 3 genotypes WEAF-B, SOAS and EAAF) between 2003 and 2004. It also confirmed wild polioviruses in 19 countries, only six of which are considered to be polio endemic; 12 countries had poliomyelitis cases caused by viruses originating in poliovirus reservoirs in northern Nigeria, and one country had a single case linked to imported virus from India.

The polio laboratory network has achieved an impressive level of proficiency, with 96% of 145 laboratories fully accredited by WHO and all program standards of performance met or surpassed. As a result of increased surveillance activity, there has been a significant increase in workload in key laboratories serving remaining endemic countries and foci. Despite this increase, laboratories have continued to improve reporting timeliness. Demands for rapid reporting of molecular sequence information have also increased dramatically, but sequencing laboratories have continued to meet these rising demands, consistently providing large volumes of detailed information for programmatic action. While laboratory performance is excellent, further improvements in timeliness are possible. These include decreasing delays caused by problems in transporting specimens and isolates to reference laboratories and decreasing reporting times for high-priority specimens and isolates.

Recommendations

Increasing the speed of detection of polioviruses

1. To minimize delays associated with the transport of poliovirus isolates to reference laboratories for intratypic differentiation (ITD) as wild or vaccine-like, the transfer of technologies to key laboratories should be continued and extended. Technology transfer should be aimed at having virus isolation and ITD procedures performed within the same facility. In particular, upgrading of the polio laboratories at the University of Ibadan, Ibadan, Nigeria and the Pasteur Institute, Dakar, Senegal to full ITD capacity should be completed as soon as possible, and by mid-2005 at the latest.

2. The "hot AFP case" concept as a means of identifying highest priority samples for rapid processing and reporting of laboratory results should be adopted, with continuing evaluation of its impact. Cases should be labelled as hot AFP cases by field surveillance personnel, based on epidemiology criteria (e.g. case has asymmetric paralysis, rapid onset of fever, no or incomplete history of polio vaccination, is aged under 2 years and/or belongs to a high-risk group or geographic area). Experiences gained with this approach in the WHO Eastern Mediterranean Region should be transferred to the African Region by the end of 2004. The WHO European Region should document its experiences using its hot case methodology to determine its potential benefit to other non-endemic regions.

3. The network should evaluate new technologic approaches for detection of poliovirus infections to reduce the time for providing laboratory results and to prepare for the post-OPV era. Evaluation should focus on three main approaches:

   1. Direct detection of polioviruses by polymerase chain reaction (PCR), and rapid culture followed by PCR.

   2. Development of PCR primers in addition to those used in the current diagnostic PCR, such as "Sabin REC" primers and genotype-specific wild poliovirus primers.

   3. Poliovirus serology for detection of anti-poliovirus IgM. Development of other technologies should also be continued and encouraged, priority being given to the development of standardized and validated methods enabling the efficient detection and characterization of vaccine-derived polioviruses (VDPVs) in clinical specimens and environmental samples.

   OPV cessation and policy development

4. The Polio eradication initiative should take every opportunity to engage the broader scientific and public health communities in discussion and technical assessment of key elements of strategies being developed for OPV cessation. As a first step, a draft of the proposed third edition of the WHO global action plan for laboratory containment of polioviruses should be widely distributed for discussion and comment before the end of 2004.

5. Key technical and operational strategies should be developed to achieve laboratory containment of OPV infectious materials. These strategies should be incorporated into the third edition of the WHO global action plan for laboratory containment of polioviruses. Particular attention should be given to outlining an effective and achievable approach for containment of OPV potentially infectious materials in the period immediately following OPV cessation.

6. WHO activities to develop model legislation for containment of wild and vaccine polioviruses should be continued. Once complete, Member States should be encouraged to adopt appropriate legal instruments to ensure full implementation of containment requirements.

7. Establishment of a database of genetic characteristics of poliovirus strains used in vaccine production should be continued and completed by the end of 2005.

8. Given the continued requirement for high-quality poliovirus surveillance after OPV cessation, WHO should establish a working group, including both laboratory and epidemiology experts, to consider post-OPV cessation surveillance requirements and develop plans of action for continued laboratory network activities and continued provision of network needs.

9. Following experience gained through the smallpox eradication program, WHO should develop an agenda for addressing remaining poliovirus research issues. Priority should be given to identifying and addressing research directed at resolving any current programmatic issues (e.g. VDPVs), but mid- to long-term research needs should also be considered. WHO should actively promote the research agenda, particularly for the resolution of current programmatic issues.

10. While maintaining polio eradication as their highest priority, WHO regional offices, in collaboration with headquarters, should begin the process of encouraging Member States and partners to progressively accept ownership of all polio network laboratories. This will include developing a strategy to persuade Member States and partners to commit to providing increased support and accept increasing responsibility for laboratory activities, functions and requirements over the next 5-10 years.

*At least two stool samples collected 1-2 days apart and within 14 days of paralysis onset.

Source: WHO Weekly Epidimiological Record, Vol 79, No 42, 2004.