Gland density was measured by counting the number of mucus pockets after carbachol stimulation for areas randomly

The etiology of influenza-like illness has been well characterized in some parts of the world, especially in temperate regions of the Northern Hemisphere.However, much less is known about the etiology of ILI in China, especially in Southeast China, which is located in a temperate region. Pudong New Area is the largest and most developed district in Shanghai, with an extremely dense population of 5.5 million in 2013, representing one-fifth of the population of Shanghai. Shanghai Dongfang Hospital and Shanghai Zhoupu Hospital have been national influenza surveillance sentinel units since 2007. As in other regions of China, ILI data from hospitals can provide valuable information that could be used for monitoring the onset of an epidemic, especially the circulation of influenza virus. However, the epidemiology in Pudong of viral etiology for ILI is poorly understood. With support from the Chinese Key SciTech Program for Infection Control, a laboratory-based influenza-like illness surveillance system was established in 2011 in Pudong New Area. We adapted multiplex RT-PCR assays for the detection of influenza virus and a number of other respiratory viruses that have recently been introduced, and these assays are also more sensitive than culture. There are multiple explanations for these differences. The differences could be due to true differences in the overall burden, to differences among study populations, or to detection methods that differed from among studies. It is difficult to compare the results, as the reported data were obtained with different detection methods or PCR primers. Future comparative studies to evaluate the sensitivity and specificity of these detection methods should clarify this issue. Second, the infection rates may vary with geographical location and with the particular period chosen for testing. Third, the patient population and its environment may influence the results. In our study, up to 1332 specimens were negative in RT-PCR although all of them matched well with the inclusion criteria for ILI. Negative findings could have resulted from the low load of viral material in samples, or to infection with bacteria or other viruses such as enterovirus. HRV was not present in 2011, but it was the second most frequently detected viral agent in both children and adults in 2012 and 2013, representing approximately 10% of all positive cases. The positive rate was lower than that found by R428 previous studies, which detected HRV in 10% to >40% of respiratory infections. HRV may circulate year-round in our region, a result found by previous studies. RSV-positive samples occurred at a low level in our study. This finding contrasts with other studies, where the predominant virus detected in children less than 5 years of age was RSV. The reason for this difference is that we did not include hospitalized children, as RSV has been shown to be a common cause of lower respiratory tract infection in children admitted to the hospital. Previous studies on RSV infections have primarily been conducted in hospitalized elderly adults with medical conditions such as cardiopulmonary diseases that may predispose them to viral infections that are relatively uncommon in the general population. In our study, a total of 22 samples revealed the presence of co-infections. In co-infection cases, influenza A virus, PIV, and RSV were found together most frequently, at rates of 36.4%. Previous studies have reported that co-infections were associated with more severe signs than mono-infections. Children were found to be more likely to be co-infected than adults in the present study. However, the subsequent clinical conditions of ILI illness patients were not obtained, and thus the association between co-infections and severe signs cannot be analyzed. We will address such research themes in the future. This study has limitations. First, no testing for other etiologies of acute respiratory illness was performed. As is generally known, respiratory viruses, bacteria and other microorganisms can cause respiratory illness with influenza-like symptoms. Without doubt, other microorganisms could have been additional pathogens in the negative specimens, and our results may underestimate the role of virus infection. Second, the histories of influenza vaccine in ILI outpatients were not obtained. Thus, the analysis of clinical characteristics in ILI patients may be biased. Third, we did not collect all ILI cases presenting at the above two sentinel sites from Monday through Sunday. Facility staffs were involved in the project on a voluntary basis, with frequent shifts of personnel to other facilities.

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