From the available data, it was estimated that 40,165 probable HFMD cases occurred in children aged less than five years from Beijing during 2012, with an incidence rate of 5.6%, which was higher than the overall level of China . CFR in children aged under two years was higher with 15.6 deaths per 100,000. Furthermore, a total of 22,105 HFMD cases were laboratory confirmed, of which nearly 35% were infected with EV71. EV71 has long been regarded as the predominant strain responsible for severe cases, outbreaks and even deaths. Therefore, the burden of HFMD has been significant in Beijing and has been posing great threats to health and safety of children under the age of five years.
Previously, attempts had been made to estimate the disease burden for pandemic influenza H1N1 2009 and seasonal influenza based on healthcare seeking behavior surveys [9, 10]. However, there have been very few studies conducted for HFMD. This is the first time a telephone survey of healthcare seeking behavior has been conducted to estimate the true burden of HFMD cases in Beijing, China. Our results showed that about 78% of parent-defined HFMD cases would consult a physician, which is higher than the consultation rate for influenza [9–11]. This is perhaps not surprising, when you consider that the most susceptible population for HFMD is children aged less than five years.
We observed that children between the age of two and four had a higher risk for HFMD than those less than two years. In China, most children start kindergarten at the age of two to three years. For children younger than two years, they are often cared for in their home by their paternal grandparents or parents. Attending kindergarten has often been considered as a risk factor for HFMD virus infection, especially for EV71, given the increased person-to-person contact that occurs in the setting [12, 13]. In China, kindergartens and childcare centers are encouraged to engage and educate parents around issues such as HFMD. It is perhaps not surprising that we found that there was a better understanding of HFMD amongst parents/guardians of children aged older than two years. Hence, the parent-definition of HFMD cases for kindergarten age children seemed to better match with the clinical definition.
Our study has several potential limitations. Theoretically, the number of probable HFMD case should be estimated based on the proportion of probable HFMD cases seeking health care. However, it was not feasible to obtain the consultation rate of probable HFMD cases as parents/guardians were unable to determine whether their children were probable cases or not. In this study, instead of using the consultation rate of probable cases of HFMD, we used the consultation rate of parent-defined HFMD cases to adjust for the number of probable cases of HFMD. The definition of parent-defined HFMD cases was so broad that such diseases as varicella or measles may have been included. As our results showed, a proportion of the parent-defined HFMD cases were not clinically diagnosed as HFMD, particularly in the younger children. This probably reflects the higher prevalence of rash-inducing infections occurring in children under 2 years, such as varicella and measles. In this study, we assumed that amongst the parent-defined HFMD cases that did not consult a physician, the ratio of probable HFMD cases and other disease cases was the same as those amongst the cases of parent-defined HFMD that did consult a physician. However, given the increased attention on HFMD in China, the proportion of probable HFMD cases among those parent-defined cases who did not consult any physicians may be smaller. Therefore, the estimated consultation rate for HFMD in our study might have been underestimated. Similar to other retrospective telephone surveys, the refusal of households to respond and the impact of recall bias may have the potential to limit our findings. As shown in the results, recall bias seems to be limited since the estimated consultation rate using a two-week recall period was not significantly different. Additionally, we assumed that there was no change in the consultation rate over time, which may limit the generalization of our findings. In support of the findings in this paper, are the results from a small cross-sectional survey of HFMD amongst children under five that was conducted in August, 2013 (unpublished). The consultation rate of parent-defined HFMD cases from this comparator survey was estimated at 75.1% (95% CI = [66.4%, 83.8%]), which is not significantly different from our results. The change in consultation rate for HFMD over time seems to be limited.