Dr. Jyh-Yuan Yang (楊志元)
HIV & Viral Emerging Infection Disease Lab.,
Centers for Disease Control,
EV71 infection has been associated with large outbreaks of HFMD and the majority of fatalities in Taiwan and other countries as well. Rapid identification of the causative agent of HFMD, particularly whether there is EV71 infection, can help clinical management by focusing attention on the possible complications and help public health authority to deploy preventive measures.
Typing of enteroviruses with type-specific monoclonal antibody and/or group-specific monoclonal antibody pool(s) by indirect immunofluorescence (IFA) is potentially more specific and less expensive. However, virus isolation is labor-intensive and time-consuming and not practical for either clinical or public health decision-making. Viral nucleic acid testing provide generally greater sensitivity than culture for throat and stool specimens. In our lab, CODEHOP, EV71 RT-PCR and EV71 real time RT-PCR are applied to detect EV, including EV71 infections. To cover different subtypes of EV71, dual probes are used in our rtRT-PCR. C1, C2, C4, C5 and B5 but B4 subtypes of EV71 can be picked up by this assay. The sensitivity is around 0.1 CCID50 EV71 and no cross reaction with other EVs (including CA16), Parechovirus, Rhinovirus, Adenovirus and Herpesvirus.
An easy-to-use, rapid and reliable diagnostic method is warranted not only in medical centers but also in local clinics during EV71 outbreaks. Based on the principle of IgM-capture ELISA, a bedside immunochromatography (ICT) kit was developed in our laboratory. Laboratory-confirmed infection with either positive EV71 culture or RT-PCR was used as the diagnostic standard. The sensitivity and specificity of the ICT kit was 84% and 77%, respectively among the cohort before 2013. ICT test on the severe suspected EV-infection cases (2015 to 2017) also show good results with 87.5 % sensitivity, 96% specificity and 93.9 % accuracy overall (n=66).
Despite all the laboratory methods for diagnosis, diagnosing an EV infection can be challenging. As asymptomatic EV infections are common, an identification of an EV in a patient sample does not prove disease causation. EV infections can also cause a wide variety of unspecific symptoms and therefore specimens may not be collected in the early phases of the symptoms for laboratory confirmation. However, identification of the enterovirus isolates help in the prevention, treatment and understanding of the infectious diseases, and even discovery of new virus isolates.
The content is authorized by Dr. Jyh-Yuan Yang on October 30, 2017.