Severe human infection with a novel avian-origin influenza A(H7N4) virus

Abstract

Human infections with influenza H7 subtypes, such as H7N9, have raised concerns worldwide. Here, we report a human infection with a novel influenza A(H7N4) virus. A 68 years-old woman with cardiovascular and cholecystic comorbidities developed rapidly progressed pneumonia with influenza-like-illness as initial symptom, recovered after 23 days-hospitalization including 8 days in ICU. Laboratory indicators for liver and blood coagulation dysfunction were observed. Oseltamivir phosphate, glucocorticoids and antibiotics were jointly implemented, with nasal catheterization of oxygen inhalation for this patient. We obtained the medical records and collected serial respiratory and blood specimens from her. We collected throat, cloacal and/or feces samples of poultry and wild birds from the patient's backyard, neighborhood, local live poultry markets (LPMs) and the nearest lake. All close contacts of the patient were followed up and sampled with throat swabs and sera. Influenza viruses and other respiratory pathogens were tested by real-time RT-PCR, viral culturing and/or sequencing for human respiratory and bird samples. Micro-neutralizing assay was performed for sera. A novel reassortant wild bird-origin H7N4 virus is identified from the patient and her backyard poultry (chickens and ducks) by sequencing, which is distinct from previously-reported avian H7N4 and H7N9 viruses. At least four folds increase of neutralizing antibodies to H7N4 was detected in her convalescent sera. No samples from close contacts, wild birds or other poultry were tested positive for H7N4 by real-time RT-PCR.

Keywords: Avian influenza virus (AIV); Epidemiology; H7N4; Human infection; Pneumonia.

Fig. 1

(Color online) Timeline of the clinical course and key indicators of the H7N4 patient.

Fig. 2

(Color online) Chest CT scans of the H7N4 patient. (a–d) Were obtained on day 5, day 7, day 11 and day 21 after illness onset, respectively. a-1, b-1, c-1, d-1: Lung window; a-2, b-2, c-2, d-2: Mediastinal window.

Fig. 3

(Color online) Phylogenetics of HA and NA genes of the novel H7N4 viruses. (a) HA; (b) NA. Maximum likelihood trees were inferred by using RAxML with GTR-Γ model. The branch of H7N4 viruses were in magenta, and the lineage of human-infecting H7N9 virus was in blue. The bootstrap values of major branches were labeled.