Clinical Features of Fatal Pandemic Influenza A/H1N1 Infection Complicated by Invasive Pulmonary Fungal Infection

BACKGROUND: Severe pneumonia caused by influenza virus infection can be secondary to invasive pulmonary fungal (IPF) infection. OBJECTIVES: This study aimed to summarize the incidence of IPF infection secondary to influenza virus infection and further explore its etiologic mechanism and high-risk factors. METHODS: All adult patients with confirmed influenza A (H1N1) virus infection admitted to the intensive care units (ICUs) of Nanjing Drum Hospital from November 2017 to March 2018 were retrospectively selected. The differences in baseline factors, risk factors, immune function and outcome parameters were studied between patients with and without IPF. RESULTS: Of the 19 critically ill patients with H1N1 infection, 11 (57.9%) developed IPF infection after 7 days of ICU admission. Two patients had proven and nine probable IPF infection. A difference in human leukocyte antigen–DR isotype (△HLA-DR; day 7–day 1) was found between the two groups. △HLA-DR (day 7–day 1) was higher in patients with no IPF infection than in those with IPF infection [(14.52 ± 14.21)% vs ( − 11.74 ± 20.22)%, P = 0.019]. The decline in HLA-DR indicated impaired immune function secondary to fungal infection in patients with H1N1 infection. CONCLUSIONS: IPF infection was diagnosed in 57.9% of critically ill patients with H1N1 virus infection after a median of 7 days following ICU admission. A continuous decline in immune function could lead to the development of IPF infections. Dynamic monitoring of immune function may help in the early detection of IPF infection.