Robert Duggan
University of Texas Medical Branch
Background: Case series of fatal Acute Influenza Virus (AIV) infections during the 2017-2018 epidemic at an academic institution. Methods: Autopsy cases were followed prospectively at University of Texas Medical Branch during the 2017-2018 Influenza epidemic. Clinical, microbiological and histologic data were analyzed. Results: A total of 123 of AIV infections were admitted to University of Texas Medical Branch Hospitals from 10/25/2017 to 05/19/2018. Eighty-one cases were due to IAV, 41 due to IBV and one case due to both IAV and IBV. All cases were confirmed by PCR. 14 cases were lethal (case-fatality rate in hospitalized patients: 11.4%), and six cases were autopsied. Age ranged from 41-77 years. Three cases (50%) were females three males (50%). All AIV infections were confirmed by PCR (three Influenza A [50%)] and three Influenza B cases [50%]). Five cases (83.3%) revealed superimposed acute bacterial bronchopneumonia. Bacterial cultures showed Methicillin-Resistant Staphylococcus aureus in four cases. Proteus mirabilis was isolated in one case while Streptococcus mitis was isolated in the 5th case. Two of the cases with acute bacterial bronchopneumonia also showed evidence of Diffuse Alveolar Damage (DAD). One case (16.7%) revealed DAD with no superimposed infections. Furthermore, all Influenza A cases revealed DAD while cases due to Influenza B only showed acute bacterial bronchopneumonia. One of the Influenza B cases showed a Desquamative Interstitial Pneumonitis (DIP) pattern. All cases had comorbidities including morbid obesity, COPD, diabetes mellitus, and congestive heart failure. Discussion: The 2017-2018 Influenza season was more active than recent influenza seasons. At University of Texas Medical Branch , we performed six autopsies of fatal AIV infections during this season, as opposed to only one case in each of the two previous seasons. The presence of DAD only in cases of Influenza A infections strongly suggests that these infections are more severe than other Influenza viruses (B and C). However, Influenza B infections can also lead to superimposed pulmonary bacterial infections and subsequent sepsis and death.