The role of supplementary environmental surveillance to complement acute flaccid paralysis surveillance for wild poliovirus in Pakistan – 2011–2013
Fig 2
Surveillance system circulation detection time of genetically-similar isolates* before polio case onset and difference in detection time between AFP and environmental surveillance overall, by year and by province environmental surveillance for Pakistan polio cases**– 2011–2013.
*Genetically-similar isolates were defined as isolates with ≥99.0% identity in VP1 capsid nucleotide sequence to the polio case isolate. **28 of 361 total polio cases (11 pairs and 2 triplets) had 100% identity in VP1 capsid nucleotide sequence with one or two other isolates. These pairs and triplets were considered together, resulting in 346 genetically-unique polio case isolate sequences for analysis. Abbreviations: ES: Environmental Surveillance; AFP: Acute Flaccid Paralysis; AFP-S: Acute Flaccid Paralysis surveillance. 1 Time (days) from first isolate within 99% of VP1 capsid detected by environmental surveillance to symptom onset date for polio case. 2 Time (days) from first isolate within 99% of VP1 capsid detected by AFP surveillance to symptom onset date for polio case. 3 Number of days sooner that environmental surveillance detected circulation before AFP surveillance; Negative numbers indicate AFP detection preceding ES detection and positive numbers indicate ES detection preceding AFP detection. 4 Polio case was reported from a province conducing environmental surveillance (i.e. Balochistan, Sindh, Punjab, Khyber Pakhtunkhwa). 5 Polio case was reported from a province not conducting ES (i.e. Federally Administered Tribal Areas, Gilgit Baltistan).