Neurovirulent vaccine-derived polioviruses in sewage from highly immune populations.

Background: Vaccine-derived polioviruses (VDPVs) have caused poliomyelitis outbreaks in communities with sub-optimal vaccination. Israeli environmental surveillance of sewage from populations with high (>95%) documented vaccine coverage of confirmed efficacy identified two separate evolutionary clusters of VDPVs: Group 1 (1998-2005, one system, population 1.6x10(6)) and Group 2 (2006, 2 systems, populations 0.

Oral poliovaccine: will it help eradicate polio or cause the next epidemic?

Background: Poliovirus rapidly evolves by nucleic acid substitutions and genetic recombination with other polioviruses and non-polio enteroviruses. Evolving oral poliovaccine can rapidly revert to neurovirulence and undergo antigenic alterations.

Objectives: To evaluate the threat of vaccine-derived poliovirus (1-15% divergence from the respective Sabin strain) for a poliomyelitis-free population in a country with a long-standing routine vaccination program.

Immune status to poliovirus among immigrant workers in Israel.

Background: An essential part of the progress towards the global eradication of poliomyelitis is the ongoing evaluation of populations immunity. Migration of unregistered individuals poses a challenge to such estimations. Moreover, partially immunized immigrants might enlarge immunity gaps and facilitate polio outbreaks in their destination countries.

When is an epidemic an epidemic?

Background: The large number of cases of West Nile fever diagnosed in Israel in 2000 once again brought into focus the confusion that frequently accompanies the use of the term "epidemic."

Objectives: To examine the different definitions of the term "epidemic" and to propose ways in which it can be used to both improve communication among professionals and provide the public with a better sense of the associated risks.

Methods: The literature was reviewed for the various definitions of the terms "epidemic" and "outbreak.