| Children’s ALRI (acute lower respiratory infection) was a common pediatric dis ease, its morbidity ranked first in all kinds of pediatric diseases. This disease could b e caused by bacteria, virus, mycoplasma, chlamydia and other pathogenic microorga nwasm infection. Virus was the most main reason why children have acute lower res piratory infection. For infants and children in all the world, especially children under the age of 2, respiratory syncytial virus (RSV) was the most main virus pathogens of acute lower respiratory infection, which would cause pneumonia and capillary bronchitis, and lead to acute bronchial asthma. With reports that it caused deaths of premature with combined broncho-pulmonary dysplasia and incomplete immune function, it was the most common infant respiratory infection deadly virus. RSV infection was very common in children, more than 90% of children had infected with RSV before the age of 2, about 50% had two or more times of infection. About a third of healthy children got the lower respiratory disease after their first RSV infection, and 0.5%～2% of children require hospitalization due to severe symptoms.In 1956, Morris, etc. separated a virus from the nasal wash specimens of a chimpanzee which appeared to have caught cold in laboratory, and it was called "chimpanzee’s cold factor" then. Soon later, Chanock, etc. separated a same virus from respiratory specimens of infant with respiratory infections (pneumonia and asthma), as the virus could cause a unique cell fusion phenomenon in cultivated cells, so it was named as respiratory syncytial virus[4]. Then, worldwide studies proved that RSV was the most main virus pathogens of acute lower respiratory infection on infants and children. In both developed countries and developing countries, in all places where etiology could be studied, RSV were found to be the most main pathogens of lower respiratory infection on infants and children, especially on small infantst[5-6]. And, unlike other respiratory virus pathogens, RSV had a special infection and morbidity form, especially in the infant group where virus could cause serious and even life-threatening lower respiratory infection, and the pathogenic mechanism of this phenomena always puzzled epidemiologists and virologists[7].RSV was a negative stranded, single-chain, enveloped RNA virus, and belongs to Paramyxoviridae, Pneumovirus. According to its antigenicity, RSV could be divided into two subtypes, A and B, and they could also be divided into different subtype strains in a same subtype. On the beginning, the two antigen subtypes of RSV was found and verified in the antibody neutralization test of two representative subtype strains, A2 and CH18537. According to the worldwide researches of molecular epidemiological, there were sequence differences between the two subtypes, which proved that they belong to two different evolution spectrum rather than just a few main antigen site variant. The genome RNA of RSV was 15200 nucleotides long, contains 10 gene, followed by NS1, NS2, N, P, M, SH, G, F, M2, L, a total of 11 kinds of protein were expressed, and the M2 gene encoding has two protein M2-1 and M2-2[8]. In RSV, the G protein was the membrane glycoprotein which was most easily to produce antigen variation, and related to the adhesion of viruses and cells, mutations between the subtypes and in subtype were great, which was an important means of RSV escaping immune attack. The G protein amino acid homology of RSV’s different subtypes was only 53%, and antigen correlation was only 5%[9].Different subtypes’G protein couldn’t provide effective cross protection, and the existence of subtypes might cause repeated RSV infectionst[10].It was reported that 20%-53% of infants in the United States would get their first lower respiratory infection in the first year after birth [11]. In our country, the number of new-born each year in China now has reached conservatively estimated more than 20 million, so at least 10 million cases of children’s lower respiratory infection would happen every year. So the morbidity quantity of the children’s lower respiratory infection was hard to imagine. In history, our country had a big children RSV infection epidemic records. According to the record, in 1971 and 1975, in Jiangxi, Zhejiang, Fujian, Shanghai, Guangxi and Guangdong, there was enzootic asthmatic pneumonia epidemics caused by RSV. While in pneumonia epidemics in 1971 and 1975, the total morbidity number was more than 100000 [7]. Although nationwide viral infections epidemic in such a large scale was not very common in later years, the lower respiratory infection caused by RSV were quite common in all parts of the country, and it has always been one of the major diseases that threaten infants’safety and health in China. The main clinical symptom of lower respiratory infection caused by RSV was asthma, and it would cause acute respiratory failure, heart failure and brain edema, even apnea and asphyxia which would lead to death when revere. RSV could be spread through close contact with patient or inhaling a large number of particles from patients’sneezing or coughing, or through contacting with the pollutants (such as the surface of the pollutants or other objects)[11].Now, RSV infection has become a serious public health problem in the world as the infection and morbidity was worldwide. There were also some local epidemics as the respiratory syncytial virus’epidemic were influenced by season and region(12-13). According to the antigenicity differences, respiratory syncytial virus was divided into two subtypes (A, B). The two subtypes could be distinguished by RT-PCR test with different primer design, however, there was mainly one subtype in the epidemic of respiratory syncytial virus in a region.RSV was widely spread and had obvious seasonal epidemic [14]. With economic development, improvement of medical level and improvements in children’s nutritional, pneumonia as the reason for our children’s cause of death decreased year by year, but lower respiratory tract infection of children’s lives and health still posed a major threat. Respiratory virus was the main pathogen of lower respiratory tract infection, it was second only to Streptococcus pneumoniae and influenza[15]. In order to understand the epidemiological characteristics of children who had lower respiratory tract infection with RSV hospitalization in Dongguan City, and provided basis for clinical prevention and treatment. This study detected infection status of respiratory tract infection which was extracted from hospitalized children nasopharyngeal of lower respiratory tract infection in Dongguan People’s Hospital from January 2013 to December 2014 by RT-PCR, and statistical analyzed the relationship between respiratory tract of RSV infection and age, gender, time of infection.[Object and method]1.Objects:collected from hospitalized children nasopharyngeal of lower respiratory tract infection in Dongguan People’s Hospital from January 2013 to December 2014, a total of 920 cases. Aged from 2 months to 11 years old, mean age (2.9+4.8), which included 560 cases of male children,360 cases of female children, all research objects for the hospital diagnosis of children were in line with corresponding lower respiratory tract infection diagnostic criteria in the 8th Edition "Zhu Futang practical Department of Pediatrics":under the age of 14 years old, they had one or a few features, such as:cough, expectoration, shortness of breath, abnormal lung auscultation breath sounds, higher than 38 oC temperature, and accompanied with typical of lower respiratory tract infection symptoms, no pulmonary diseases and infected with other systems, it was diagnosed as bronchitis, capillary bronchitis, pneumonia and other lower respiratory tract infection. Other diseases affecting the heart and lung function were excluded, such as:congenital heart disease, occlusion of bronchiolitis, bullae of lung, bronchiectasis, bronchopulmonary dysplasia and immunodeficiency diseases.2. Methods:Collected one tube of the nasopharyngeal swab specimen of each sick child that was included as the objects of study and preserved in the refrigerator under 4 ℃. Conducted RNA extraction and reverse transcription synthesis of the nasopharyngeal secretion specimens within 48h in strict accordance with the kit instruction. RNA extraction and reverse transcription synthesis kits were provided by Da An Gene Co., Ltd of Sun Yat-sen University, and nucleic acid detection kits for respiratory syncytial virus (PCR- fluorescence probe method) provided by Da An Gene Co. Ltd of Sun Yat-sen University were used for amplification. RT-PCR amplification methods:the reaction conditions were as follows:one loop for 15min under 50℃, one loop for 15min under 95 ℃, and 40 loops for 15s under 94℃ followed by 45s under 55 ℃ (to collect the fluorescence). The nucleic acid detection kits for respiratory syncytial virus (PCR-fluorescence probe method) were provided by Da An Gene Co. Ltd of Sun Yat-sen University, and the PCR premiers were supplied by Shanghai Sangon Biotechnology Co., LTD. All operations were performed by the same clinical laboratory staff with intermediate certificate in strict accordance with the kit instruction.3.Data analysis:used SPSS19.0 to statistic, took the percentage (%) to express the count data, the application of x2 test, took P<0.05 as statistical significance of the test standard.[Result]All together 920 eligible children cases were included as the objects of study with the age range of 2 months to 11 years old and an average of 2.9±4.8 years old. There were 560 male children cases,360 female cases, and 194 cases with positive respiratory syncytial virus detection, among which 134 were male and 60 were female. There were 32 cases with severe pneumonia (all of whom were children under 2 years old), accounting for 16.49%, with the male and female cases of 25 and 7, respectively. There was no statistical difference of the rate of different subtypes in children with severe pneumonia that was caused by RSV.1.Analysis of positive detection rate and gender of hospitalization children: there were 194 cases of hospitalized children with RSV positive of lower respiratory tract infection in Dongguan City People’s Hospital, and the total of positive rate with RSV was 21.09%, A type for 149 cases, which occupied 76.80%, B type for 45 cases, which occupied 23.20%. Male children were 134 cases, positive rate was 23.93%; female children were 60 cases, the positive rate was 16.67%. There was a significant difference between the positive rate of RSV in male children and the positive rate of female children (x2=4.812, P< 0.05)2. The relationship between positive detection rate and the age of hospitalized children:520 cases were children under age of 2 years, the positive rate was 2, 27.69%,400 cases were children older than age of 2 years, the positive rate was 12.50%. The positive rate of RSV in children under age of 2 years was significantly higher than that of children above age of 2 years, and the difference had statistically significant(x2=4.812, P<0.05).3. The relationship between positive detection rate and year of hospitalized children:there were 440 cases of hospitalized children with lower respiratory tract infection in Dongguan City People’s Hospital of 2013, RSV positive rate of 94 cases, accounted for 21.36%; there were 480 cases of hospitalized children with lower respiratory tract infection in Dongguan City People’s Hospital of 2014, RSV positive rate of 100 cases, accounted for 20.83%; There was no significant difference in the positive rates of RSV in 2 years (x2=0.019, P>0.05)4.The relationship between positive detection rate and month of hospitalized children:there was no significant difference in the positive rates of RSV for hospitalized children with lower respiratory tract infection of Dongguan City People’s Hospital in October-December and January-March (x2=0.082, P> 0.05);there was no significant difference in the positive rates of RSV for hospitalized children with lower respiratory tract infection of Dongguan City People’s Hospital in April-June and July-September(x2=0.107, P>0.05);However, there was a significant difference in the positive rates of RSV between October-December with January-March and April-June with July-September (x2=14.938, P＜0.05)[Conclusion]1.In Dongguan People’s Hospital, RSV infection of children with lower respiratory tract infection were mainly A in 2013-2014, the quantity of male were more than female.2.Children with severe pneumonia that was caused by RSV were under 2 years, and there was no statistical difference of the rate of different subtypes of severe pneumonia caused by RSV.3.Among children with lower respiratory tract infections, the rate of RSV infection in children under age of 2 years was more than that of children above age of 2 years.4.In the Dongguan area, RSV infection of children were roughly same in 2013 and 2014, there was not large-scale outbreak of the epidemic.5.RSV infection rate of children in winter season (October～December with January-March) was larger than that in summer and autumn (April-June with July-September), guiding parents to do preventive work. |
