Mild infection of a novel H7N9 avian influenza virus in children in Shanghai

Yu, Xuelian; Zhang, Xi; He, Yi; Wu, Huanyu; Gao, Xia; Pan, Qichao; Shen, Jiaren; Zhu, Jianming; Chen, Hongyou; Zhu, Yiyi; Wu, Fan; Wang, Jianwei; Yuan, Zhengan

Studies from AIV H5N1 infections identified several patients that were 5 years or younger. 8 Severe acute respiratory syndrome patients 12 years or younger were associated with milder disease. 9 A similar phenomenon was observed in H7N9 infections. The H7N9 mild cases were males below 4 years of age, while the severe patients were all adults, with a sex ratio of 2.4 (M/F, 12 : 5). Compared with the median age of severe patients (67 years old), the patients who died were older (74 years old). People older than 50 seemed to be at an increased risk for infection with the novel H7N9 virus. The same phenomenon was reported in other Chinese provinces, such as Zhejiang, Jiangsu, Anhui and Henan. 10 The age distribution of H7N9-infected patients is also similar to previous seasonal influenzas, but is different from the 2009 pandemic H1N1 influenza [A(H1N1) pdm/09]. 11 Patients older than 50 appeared to experience more severe illness in H7N9 infection. All 19 patients who fit this criterion suffered from high fever. The median body temperature in mild, severe and fatal H7N9-infected cases were similar, and all were significantly higher than in A(H1N1)pdm/09 infections. 11 Both mild patients developed pharyngalgia and tonsillitis (II 6 ), while only one severe and one fatal case displayed pharyngalgia; no severe or fatal cases developed tonsillitis. Cough was the most common symptom in both severe (six) and fatal (eight) infections; three severe and seven fatal cases displayed a productive cough. Compared with the severe H7N9-infected patients, more patients that died experienced chill, dyspena, fatigue, chest stuffiness, somnolence and arthralgia, while less patients who died suffered from diarrhea, muscle ache and runny nose. The details are listed in Table 1 . Conjunctivitis, which is common in human infections with other H7 1,2 viruses, was not documented in H7N9-infected patients.