Long persistence of EV71 specific nucleotides in respiratory and feces samples of the patients with Hand-Foot-Mouth Disease after recovery

Background: EV71 is associated with the fatal cases of brain stem encephalitis during large HFMD outbreaks from 1998 to 2008. EV71 may continuously shed from upper respiratory tracts and feces of HFMD patients for relatively long time after recovery. However, the persistence of viruses in the patients' secretions and excretions is not clear. Methods: Serial throat swabs and feces of 34 definitely diagnosed patients, including 30 mild cases and 4 severe cases, were traced and collected with the interval of 2 to 4 days for up to 32 and 48 days, respectively, and tested by a nested RT-PCR. Results: The EV-71 specific sequences were identified by a Nested RT-PCR in all specimens of 0-4 days, and 5-8 days. The positive rates of EV71 in throat swabs dropped markedly to 42.86% during 9-12 days, and maintained at 20-30% during 13-24 days, while that in feces reduced to 71.43% during 9-12 days, and maintained roughly 20% till 37-40 days. EV71 nucleotide of 36.36% cases disappeared simultaneously both in throats and feces, 39.39% cases showed longer persistence of EV71 nucleotides in feces, and 21.21% were longer in throats. The longest duration of shedding observed was 24 days for throat swabs and 42 days for fecal specimens. Conclusions: EV71 shedding from respiratory tract may continue for nearly four weeks after onset, but its excretion through feces can persist more than five weeks.