A Study On The Correlation Between Enterovirus 71 And Acute Respiratory Tract Infections In Children

Acute respiratory tract infections (ARTIs) is one of the major causes of morbidity and mortality of children in developing countries. Every year, about 1.9 million children under 5 years old die for acute lower respiratory tract infections worldwide. The mortality is especially high in developing countries. The common causes are infections of viruses, bacteria and Chlamydia. Virus infections include infection caused by respiratory syncytial virus, influenza virus, parainfluenza virus, adenovirus, metapneumovirus etc. Recent studies show that enterovirus plays important role in ARTIs in children too.Enteroviruses (EV) are member of small RNA viruses family. About 70 serum types of human EVs were identified so far. On the basis of their pathogenesis in humans and experimental animals, the EVs were originally classified into four groups, polioviruses (3 serum types), coxsackievirus A (24 serum types), coxsackievirus B (6 serum types), and echoviruses (33 types). After 1969, the new identified EVs were not classified into groups, but names with a system of consecutive numbers: EV68～71. Recent attention was raised for the hand, foot and mouse disease (HFMD) and neurological infection caused by enterovirus 71 (EV71). EV71 is a small RNA virus branch, a member of an intestinal virus. EV71 was first isolated and characterized from an infant case of neurogological disease in California in 1969. It spread out all over the world after then. It was reported that EV71 is responsible for over 10 large epidemics and major outbreaks worldwide. EV71 infection may be asymptomatic of myclonic epilepsy, encephalitis, acute flaccid paralysis, cardiorespiratory failure and pulmonary edema etc. Since 1999, China's Guangdong, Fujian, Shanghai, Chongqing and other regions have reported local epidemics. It was found that EV71 is one of the major pathogens for HFMD in southern China. In spring of 2008, the HFMD epidemics in Fuyang, Anhui caused 489,073 HFMD cases, include 126 deaths. The mortality rate is 0.0095 per 100,000, case fatality ratio is 0.26 per 1000. Laboratory results showed that EV71 was the major pathogen.The spread of EV is through respiratory, gastrointestinal. EV can cause individual disease or epidemic. Children are the susceptible crowd. Since the lack of sensitivity of traditional diagnosis, EV is underestimated in respiratory infections. Recent studies shows that about 10~15% of virus associated ARTIs in children are caused by EV, only next to respiratory syncytial virus,adenovirus and influenza virus. EV is also a major pathogen of children acute asthmatic diseases, e.g. capillary bronchitis, acute asthma etc. Some morbidity and mortality cases related with HMFD were reported nationwide this year. It is obvious that EV71 is dangerous to young children. Therefore, it is urgent and very necessary to further study the infections of EV71..Objectives:To investigate the enterovirus (EV71) in the correlation with ARTIs in children, the distribution among month, age and sex and clinical features, nasopharyngeal secretions were obtained from children with ARTI, virus isolation and reverse transcription polymerase chain reaction (RT-PCR) were used to detect EV.Experiment Methods:1,Virus Isolation: Target crowd is the inpatient children with ARTIs of the Respiratory Department of Changchun Children Hospital from July 2008 to January 2009. Total 110 cases include upper respiratory tract infection, capillary bronchitis and pneumonia children. Throat swab specimens were collected 3 days after patients were admitted. Among them, 42 were inoculated with RD cell, cultured under 36℃. The cell culture tubes were observed daily under inverted microscope to catch the characterized cytophathic effect (CPE).2,Reverse Transcription Polymerase Chain Reaction (RT-PCR):After extracting the strain nucleic acid RNA from the 110 original throat swab specimens and positive strain after strain isolation, amplified with EV71 specific primer with RT-PCR. Compared it with the supernatant of cultured EV71 virus BrCr. Use agarose gel electrophoresis to analyze the amplification product, observe the results with UV lamp and analyze the data.Results: 42 throat swab specimens were performed virus isolation. 3 cases are positive. The positive ratio is 7.14%(3/42). 110 specimens were detected with RT-PCR, 14 of them showed characterized 226 bp amplified fragments. Positive ratio is 12.73%(14/110). The 14 cases include 3 cases with virus isolation mentioned above. It shows that the RT-PCR is more sensitive than virus isolation. As for the month of EV71 infection, October is an obvious peak for infection. The ratio between male and female is 1.3:1, there is no significant differences (p>0.05) between different sexes. For children of different ages, 13 cases came from less than 3-year-old, 1 case came from that over 4 years old. It shows that children of less than 3-year-old are the susceptible crowd. Major clinical symptoms of ARTI caused by EV71 are cough(100%), asthma(71.43%),and fever(35.71%) and so on. There is no significant difference between clinical symptoms.Conclusions:1,EV71 can cause ARTI in children. This study shows that EV71 infection does associate with ARTI in children. There are 13 cases are from less than 3-year-old in the 14 positive children. It shows EV71 infection mainly affects infant or toddler.2,ARTI caused by EV71 does not differ significantly in clinical symptoms. Major symptoms are cough, asthma. Some children come with fever, or diarrhea, rash, which is different from rash caused by EV71 related HMFD. It is not easy to distinguish from other virus infection. 3,Using RT-PCR with EV71 specific primer to detect EV71 is more selective and sensitive, can be applied to wide variety of specimens. The 14 cases, including 3 cases with virus isolation mentioned above, showed the merit of RT-PCR vs. virus isolation in early diagnosis.