Rapid risk assessment: Influenza-associated invasive pulmonary aspergillosis, Europe

Although the association of influenza with an increased risk for bacterial superinfections is well known, the risk of developing a fungal disease such as invasive pulmonary aspergillosis (IPA) is less well characterised. In recent years, cases of influenza-associated IPA have been reported from several countries with increasing frequency. The evidence base for an association between influenza infection and IPA among severely ill patients admitted to hospital intensive care units (ICUs) is convincing, despite the fact that the studies conducted so far have limitations with regard to sample size, study design, and criteria used for diagnosis.

The diagnosis of IPA requires clinicians’ awareness in order to conduct timely and appropriate testing. As IPA has traditionally been considered a disease occurring only in severely immunocompromised patients, ICU physicians might not suspect IPA in severely ill influenza patients without additional immunosuppression or classic risk factors. Influenza-associated IPA might therefore be underdiagnosed or diagnosed with a delay, possibly leading to worse patient outcomes. Furthermore, the published literature only discusses ICU-admitted cases; however, the short interval between ICU admission and diagnosis of IPA in the most recent studies suggests that efforts should be enhanced to understand the magnitude of the problem, also among other hospitalised severe influenza cases.

During the 2017–18 influenza season, a total of 9 317 laboratory-confirmed cases of influenza were reported to ECDC from ICUs in 10 EU Member States participating in the surveillance of severe influenza. In most of these 10 Member States, only a selected number of ICUs participate in this surveillance scheme. Therefore, the actual number of ICU admissions of influenza patients in the 28 EU Member States during a severe influenza season such as 2017–18 will be in the order of tens of thousands of confirmed cases. Current data are insufficient to accurately estimate the frequency of influenza-associated IPA; incidence might vary widely between hospitals and countries. However, a recent multicentre study in Belgium and the Netherlands showed that a considerable proportion of severe influenza cases may develop IPA as a superinfection, increasing the likelihood of poor outcomes. Therefore, the timely and appropriate diagnosis and management of IPA could result in improved outcomes among severely ill influenza patients in ICUs.

Due to the association of severe influenza infections with IPA among ICU-admitted patients, its early occurrence after ICU admission, and the associated poor outcomes, public health authorities should raise awareness about this issue among ICU physicians and clinical microbiologists. For options for response, please see the respective section in this document. 

RAPID