Characteristics and Outcomes of Influenza a Infection in Hematologic Malignancy (HM) Patients and Hematopoietic Stem Cell Transplant

Background

Influenza is one of the most common virus causing respiratory tract infection in HM patients and HSCT recipients. Severely immunocompromised pts suffer more severe disease, prolonged viral shedding, emergence of resistance as well as higher mortality rate. Studies comparing characteristics and outcomes of pandemic H1N1 and seasonal influenza (SFlu) in HM patients versus HSCT recipients are lacking.

Methods

We evaluated characteristics, diagnostic results, management and outcomes of all influenza A infections (pandemic H1N1 versus SFlu) and determined the risk factors associated with pneumonia and all-cause mortality in HM patient and HSCT recipients at MD Anderson Cancer Center (MDACC) from April 2009 to July 2013. 

Results

A total of 259 patients were identified, including 134 (52%) HM patients and 125 (48%) HSCT recipients. Majority of patients (242, 93%) were adults, males (147, 57%) with underlying diseases in remission (160, 64%). About half of patients required hospitalization for outcomes including pneumonia 28% (72 pts) and death 6% (16 pts). Majority of patients (214, 83%) received antiviral therapy within a median of 3 days (range, 0d – 28d) after onset of first symptom. Compared to HCT recipients, a significantly higher percentage of HM pts were in active stages of cancer with severe neutropenia (26, 20%) and severe lymphopenia (25, 19%) and required hospitalization (76, 57%).  Multivariable logistic regression analysis identified hematologic malignancy (AOR: 2.5 (95% CI: 1.2, 5.28), decreased albumin (AOR: 2.2 (95% CI: 1.0, 4.64), and delay in initiation of antiviral therapy (AOR: 1.3 (95% CI: 1.12, 1.47) as significant risk factors for development of pneumonia (P = 0.05), after adjusting for the virus strain. Interestingly, H1N1 infections were more prevalent in Hispanic population (26, 31%) and required more mechanical ventilation (9, 11%) compared to SFlu, but no significant differences were observed with respect to pneumonia or mortality between these two viruses. 

Conclusions

Influenza remains a significant cause of morbidity and mortality in HM patients and HSCT recipients. Compared to HCT recipients, HM patients were more likely to progress to pneumonia, probably owing to active cancer stage and pancytopenia. H1N1 patients did not have higher mortality rate compared to SFlu in either of the groups. Early antiviral therapy remains crucial in preventing morbidity in this population.