Hospital-based Influenza Morbidity and Mortality (HIMM) Surveillance for A/H7N9 Influenza Virus Infection in Returning Travelers

Song, Joon Young; Noh, Ji Yun; Lee, Jacob; Woo, Heung Jeong; Lee, Jin Soo; Wie, Seong-Heon; Kim, Young Keun; Jeong, Hye Won; Kim, Shin Woo; Lee, Sun Hee; Park, Kyung-Hwa; Kang, Seong Hui; Kee, Sae Yoon; Kim, Tae Hyong; Choo, Eun Ju; Lee, Han Sol; Choi, Won Suk; Cheong, Hee Jin; Kim, Woo Joo

Foreign travel information was collected from the patients with ILI. If the patient visited China, Hong Kong, or neighboring Southeast Asian countries within seven days before ILI development, respiratory specimens were collected using virus transport medium after informed consent. ILI was defined as sudden onset of fever (> 37.8°C) accompanied by at least one respiratory symptom (cough and/or sore throat). 1 After enrollment, a rapid influenza antigen test was administered for seasonal influenza viruses, and respiratory specimens were transported to the central laboratory (Korea University Guro Hospital). All cases were tested for A/H7N9 influenza virus using the World Health Organization (WHO) real-time polymerase chain reaction (PCR) protocol. 3 At the same time, the presence of seasonal influenza virus (A/B), respiratory syncytial virus (A/B), parainfluenza virus (type 1-4), adenovirus, human rhinovirus, human metapneumovirus, human coronavirus (hCoV-229E, hCoV-OC43), human bocavirus, and enterovirus was determined using the Seeplex ® RV15 PCR assay (Seegene Inc., Seoul, Korea) as described previously. 4 For test-negative cases, real-time PCR assays were conducted to detect enterovirus D68, WU polyomavirus, KI polyomavirus, parechovirus (type 1, 3, and 6), and pteropine orthoreovirus using primers presented in Table 1 . [5] [6] [7] [8] During the study period between October 1st, 2013 and April 30th, 2016, 11 patients presented with ILI within seven days from travel return ( Table 2) . Seven (63.6%) of the 11 patients visited eastern China where avian A/H7N9 influenza virus was prevalent ( Table 2) . The other four patients visited Hong Kong (n = 2), Malaysia (n = 1), Cambodia (n = 1), and Vietnam (n = 1). Seasonal influenza virus was the most common cause of ILI among returning travelers. Seasonal influenza viruses were isolated from six patients (54.5%): four with A/H1N1 and two with A/H3N2 influenza viruses ( Table 2) . No other respiratory viruses, including avian A/ H7N9 influenza virus, were detected. As previously reported, 9 the majority of H7N9 human cases developed after visiting live poultry markets in China; in this study, none of the eleven patients visited a livestock market while they travelled abroad ( Table 2) . Since the first report of human A/H7N9 cases in China in February 2013, the virus has been detected in domestic poultry exclusively in eastern China with limited detection in migratory wild birds according to surveillance studies. 9,10 Thus, contrary to avian A/H5N1 influenza viruses that have spread worldwide, avian H7N9 influenza viruses are, at least currently, confined within China. Actually, less than 5% of human A/H7N9 cases have been reported in countries other than China, including Hong Kong, Taiwan, Malaysia, and Canada, and all of these patients travelled to China prior to illness onset. 9,11 However, H7N9 influenza viruses are genetically more humanadapted compared to H5N1 influenza viruses, and H7N9 influenza viruses are reported to cause human infection even after casual contact such as walking through a livestock market without direct close contact. 9,10 In a similar time frame, the incidence of H7N9 human infection was 10 times higher than that of H5N1 infection. 9 Although limited to eastern China as of yet, avian H7N9 influenza virus is considered to have the highest pandemic potential among currently 3/5 https://jkms.org https://doi.org/10.3346/jkms.2018.33.e49