It was reported that most children experiencing infection of EV71 will cease shedding virus particles within 13 to 24 days after the disease onset . The longest EV71-positive time in throat swab was reported 24 days and in feces 42 days after onset . However no one reported how long the severe cases, mild cases, close contacts shed virus. This study examined the duration of EV71 excretion in sequential fecal specimens and throat swabs from mild cases, severe cases and close contacts which were definitely EV71 positive.
Using the data of this study and the Kruskal-Wallis Test, the results showed that significant difference of the duration of EV71 shedding was found among severe cases, mild cases and close contacts. This phenomenon is different from some other virus such as HAV, rotavirus, the excretion of which does not show any correlation with the severity of the disease [16, 17]. Whether or not the duration of HAV excretion is correlated with the age of the patients has been reported previously [16, 18]. However, the obtained results were different. Since the sample size was small, our data did not provide the information of whether the factors of age and sex influence the duration of the virus shedding. The reasons why the EV71 shedding was different among severe cases, mild cases and close contacts remain to be elucidated.
This study showed that the longest duration of EV71 shedding in fecal sample is 54 days and 30 days in throat swabs. Some researchers have reported that enterovirus shedding in fecal samples lasts for a longer period than in throat swabs [15, 19, 20]. EV71 is transmitted predominantly via the faeco-oral route. Prolonged excretion of EV71 will act as an on-going infection source which will play an important role in outbreaks of HFMD. This study showed that some individuals shed other enterovirus in the fecal samples after EV71 could not be detected. In this study we also found that EV71, just like rotavirus  or poliovirus , has a phenomenon of excreting virus intermittently both in fecal samples and in throat swabs after apparent recovery from initial infection. Children or adults excreting EV71 intermittently for a long time may serve as reservoirs of the virus and thus contribute to the epidemic of the HFMD.
The findings in our study suggest that patients may excrete EV71 for a long period. It means that the majority of severe cases may still be infectious during their recovery even though they are asymptomatic. The role of these prolonged excretion in perpetuating epidemics of HFMD is uncertain. In order to thoroughly eliminate the potential infective sources from the community, one solution might be for cases to be separated from other susceptible children until patients no longer excreting virus, especially for severe cases. In this study we also found that some cases were EV71 positive before they showed the typical HFMD symptoms. This phenomenon implied that cases began to excrete EV71 just at the latent period. It was a blind spot for disease prevention. So we suggest that it is necessary to make preventive measures such as sanitation, disinfection and hand-washing, especially among people at risk such as children under the age of five years old. Timely preventive measures will limit secondary cases of HFMD.