Human co-infection with novel avian influenza A H7N9 and influenza A H3N2 viruses in Jiangsu province, China

In February, 2013, a novel avian infl uenza A H7N9 virus emerged in east China and quickly spread to other areas. By May 27, 130 human infections had been confi rmed, with 37 deaths. Transmission can occur through direct or close contact with poultry or through exposure to environments that are contaminated with poultry. No human-to-human trans mission has been reported. Coinfection of viruses in human beings, birds, or other animals provides the possibility for the emergence of a new reassortant virus. Here, we report human co-infection with novel H7N9 and seasonal infl uenza A H3N2 viruses. On April 25, 2013, a previously healthy 15-year-old male student began to have infl uenza-like symptoms of fever, mild cough, headache, and sore throat. The patient did not report a history of contact with sick persons or animals. Retrospective investigation showed that none of his close contacts developed infl uenza-like symptoms. The patient went to a local hospital on April 26 when he felt that his symptoms were getting worse. On physical examination, his temperature was 39·0°C. The white blood cell count was 5·63 cells × 109/L with 65% neutrophils and 21% lymphocytes. The patient was admitted to hospital and received oseltamivir 75 mg twice daily to alleviate symptoms. He recovered on May 2. Two throat swabs were collected on his fi rst visit to the hospital on April 26. One specimen was used for the detection of infl uenza A and B virus by a rapid, point-ofcare colloid gold assay (ABON, Alere Inc, Hangzhou, China), which was positive for infl uenza A. The other specimen was sent to the Nanjing Municipal Center for Disease Control and Prevention (NJCDC), where subtypespecifi c primers provided by the China CDC were used to detect seasonal infl uenza viruses (H1 and H3), pdm2009 H1N1, and avian infl uenza virus subtypes (H5N1, H9N2, and H7N9) on an ABI 7500 real-time PCR system. The Ct values of general infl uenza A, H7, and H3 were 18, 30, and 18 respectively. The remainder of the sample following this analysis was then sent to the Jiangsu Provincial CDC for confi rmation of these fi ndings. We isolated virus from this specimen using Madin-Darby canine kidney cells. Further sequence analysis of RNA extracted from the cell culture supernatants on MiSeq platform (Illumina inc., San Diego, CA, USA) and ABI 3130 automatic DNA analyzer (Life Technologies, Applied Biosystems, Foster City, CA, USA) showed that H3, N2, H7, and N9 genes coexisted in the sample. Nucleoid acid sequence comparison of the H7 and N9 genes of the H7N9 viruses isolated from the patient (A/Nanjing/M2/2013, GISAID accession number EPI450526 and EPI450527) and em erging H7N9 virus (A/Zhejiang/DTID-ZJU01/2013[H7N9]) showed that simi larity was 99·9% and 99·8%, respectively. The similarity of H3 and N2 genes of the H3N2 viruses isolated from the patient (A/Nanjing/M1/2013, GISAID accession number EPI450524 and EPI450525) and currently circulating seasonal H3N2 virus (A/Texas/ JMM_21/ 2012[H3N2]) was 99·5% and 99·8%, respectively. Since mid-April, 2013 (fi gure, appendix), pdm2009 H1N1 has replaced H3N2 to become the dominant strain in Jiangsu Province, China. So far no co-infection of H7N9 and H3N2 viruses has been reported. However, dual infl uenza virus infec tions are a potential source for virus reassort ment between a human and an avian viral strain. The fi nding of human co-infection with H7N9 and H3N2 viruses shows that human beings could act as mixing vessels for virus reassortment, which might facilitate human-to-human transmission. The public health and scientifi c com mun ities should enhance surveillance for virus evolution.