The authors reply

摘要

We thank Dr. Cruz for his interest in our study. In his letter, Dr. Cruz notes that the 1987 article by Cruz et al. on the epidemiology of poliomyelitis in Guatemala in 1982 and 1983 described some observations that may have foreshadowed the recognition of circulating vaccine-derived polio-viruses (cVDPVs) after the 2000-2001 cVDPV outbreak in Hispaniola. The report by Cruz et al. represents an important landmark documenting the intensity of wild polio-virus endemicity in Guatemala before the 1985 initiative by the Pan American Health Organization to eradicate wild polio viruses from the Americas . The success of the Pan American Health Organization initiative, achieved in 1991, was preceded by eradication in Guatemala of the indigenous wild poliovirus type 1 in 1987 and wild poliovirus type 3 in 1990 . Interestingly, Cruz et al. found no evidence of wild poliovirus type 2 circulation in Guatemala (subsequent region-wide surveillance by the countries in the Pan American Health Organization found wild poliovirus type 2 only in the northern Andean countries in 1986-1989), but they found 5 unvaccinated paralyzed children who were excreting poliovirus related to the Sabin 2 oral poliovirus vaccine (OPV), raising the possibility of Sabin 2 OPV circulation . Their conjecture is plausible, as subsequent findings have shown that the large majority of cVDPV outbreaks are associated with poliovirus type 2 and occur in settings in which cessation of wild poliovirus type 2 circulation precludes continued acquisition of natural immunity to poliovirus type 2 and in which OPV coverage is suboptimal. These are conditions that apparently prevailed in Guatemala in 1982-1983. However, as Dr. Cruz noted , it is not possible to confirm past type 2 cVDPV circulation in Guatemala because the relevant isolates are no longer available for genetic analysis.