Severe 2009 pandemic influenza A (H1N1) infection and increased mortality in patients with late and advanced HIV disease.

Objective: To describe the clinical course of infection by 2009 (H1N1) influenza virus in different stages of HIV disease.

Design: Prospective, observational study.

Methods: During the pandemic period, HIV-infected patients presenting respiratory symptoms at a third level referral hospital in Mexico City were tested for 2009 influenza A (H1N1) viral RNA. Clinical files were prospectively analyzed.

Results: Infection by H1N1 was confirmed in 30 (23.8%) of the total 126 HIV-infected patients studied. In the group of patients with 2009 H1N1 virus infection, 16 (53.3%) were hospitalized, 12 (40%) had active opportunistic infections and six (20%) died. In the group of 96 patients not infected with 2009 H1N1 virus, 54 (56.25%) were hospitalized with opportunistic infections and 12 (12.5%) died. For all hospitalized patients, being on HAART and having undetectable HIV viral loads at hospitalization was associated with higher survival (P = 0.019). Patients with 2009 H1N1 virus infection had a higher mortality rate, even after adjusting for HAART (P = 0.043). Coinfection by HIV and H1N1 2009 virus was more severe in patients with opportunistic infections, as shown by longer hospital stays (P = 0.0013), higher rates of hospitalization (P < 0.0001), use of mechanical ventilation (P = 0.0086) and death (P = 0.026). Delayed administration of oseltamivir in hospitalized patients was significantly associated with mortality (P = 0.0022).

Conclusion: Our data suggest that infection by 2009 H1N1 is more severe in HIV-infected patients with late and advanced HIV disease than in well controlled patients under HAART.