Figure 2.

Enteroviruses isolated through Haïti poliovirus environmental surveillance during March 2017–December 2019 by year, epidemiological week, and sampling site. Orange shading for months in 2018 and May 2019 indicates periods of tetanus–diphtheria outbreak response campaigns in certain regions, which provided an opportunity for intensified all-antigen vaccination, and for July–September 2019 indicates the approximate time period of a nationwide supplementary immunization activity targeting children 2–59 months of age with bivalent oral polio vaccine (bOPV, containing Sabin strain serotypes 1 and 3). NPEV = non-polio enterovirus; SL1 = Sabin-like poliovirus of serotype 1; SL3 = Sabin-like poliovirus of serotype 3.