Among the 975 infants, a total of 143 HFMD cases were
detected during the retrospective survey period from September
2007 to October 2010 (Figure 1), including 11 inpatients, 126
outpatients, and 6 patients whose families did not seek medical
intervention. However, only 16 out of 143 cases were reported to
the National Infectious Disease Information Management System
with a report rate of 11.2% (16/143). Among the 143 HFMD
cases, 99 (69.2%) and 90 (62.9%) cases had EV71 and CoxA16
neutralizing antibody titers increased at least 4-fold after illness,
respectively. There were 54 (37.8%) cases had at least 4-fold
increase in the two antibody titers, and only 8 (0.6%) cases had
neither EV71 nor CoxA16 neutralizing antibody titer increased
after illness. Other 695 infants were of non-HFMD infection with
EV71 and/or CoxA16, of which 414 (59.6%), 154 (22.1%), and
127 (18.3%) infants demonstrated positive antibody titers for both
EV71 and CoxA16, EV71 alone, and CoxA16 alone, respectively.
Although up to 85.9% (838/975) of the infants were infected by
EV71 and/or CoxA16 during the survey period, only a small
number of them showed clinical manifestations of HFMD, and