According to a recent article
published online in Intensive Care Medicine
, co-infection occurs commonly in patients with influenza-related infections that require intensive care unit (ICU) admission.
“Although primary viral pneumonia may evolve towards acute respiratory distress syndrome and death, bacterial co-infection is frequently described in these cases, may contribute to the development of ARDS and respiratory failure, and is clearly associated with higher mortality,” write Charles-Edouard Luyt, MD, PhD, from Université Paris 06, France, and Todd W. Rice, MD, from Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
Influenza infection causes widespread epidemics each year. Bacterial co-infections also occur commonly in these cases, representing a major cause of the high morbidity and mortality associated with influenza epidemics. Indeed, bacterial co-infection complicated most of the deaths
that occurred in the 1918 influenza pandemic.
Dr. Luyt and Dr. Rice highlight data from a recent meta-analysis
, showing that co-infection rates range between 2 and 65%. They note that different sampling methods and the timing of obtaining samples could account for this disparity. Factors such as prehospital antibiotic administration, and whether a bacterial co-infection was microbiologically confirmed, could also contribute.
The authors discuss the results of a Spanish study
in patients with influenza infection who were hospitalized. Of 2,901 patients, 16.6% had a community-acquired co-infection. The researchers found that Streptococcus pneumoniae
was most commonly involved, followed by Pseudomonas aeruginosa,
and methicillin-susceptible Staphylococcus aureus
(MSSA). Interestingly, the rate of P. aeruginosa
co-infection was 14.1%—much higher than what has been previously reported
for co-infections with this organism, which have included rates of 1.3% in patients with community-acquired pneumonia, and 8.3% in patients with healthcare-associated pneumonia (HCAP). The rate of Aspergillus
co-infection was also high (7.2%). This is also unexpected, the authors say, because although invasive pulmonary aspergillosis can occur in patients with influenza pneumonia, it typically arises as a secondary fungal infection, rather than a community-acquired co-infection.