1135. Epidemiology of Past-Season Influenza strains at Detroit Medical Center
Session: Poster Abstract Session: Influenza and H1N1 Diagnosis, Epidemiology, and Viral Outcome
Saturday, October 22, 2011
Room: Poster Hall B1
Background: During the post pandemic period in Southeast Michigan, i.e. from 08/2010 and on, three circulating strains were recovered from influenza-confirmed cases: 1) 2009 H1N1, 2) seasonal influenza (Flu) (H3N2), and 3) Flu B. Our study aimed to compare the epidemiological characteristics of the three circulating strains during the post-pandemic period.

Methods: Nasopharyngeal samples sent to the Detroit Medical Center (DMC) central microbiology laboratory from the past season (12/2010-04/2011) for adults with influenza-like illness were reviewed. Strains were detected by using a universal ELISA (for both Flu A and B) and PCR tests (for 2009 H1N1 and a universal Flu A PCR). A positive PCR test for universal Flu A, in the presence of a negative test for 2009 H1N1, was indicative of a seasonal strain based on local epidemiology and initial confirmation by the Michigan State laboratories. Epidemiologic data were extracted from patients' charts and pharmacy records.

Results: Records for 205 adults evaluated in the inpatient or emergency departments with confirmed flu were reviewed during the study period. 137 patients had Flu A 2009 H1N1, 43 had Flu A H3N2, and 25 had Flu B. No significant differences in presenting symptoms were noted including fever, headache, myalgias, shortness of breath, infiltrates on chest x-ray and altered mental status. However, patient characteristics and course of illness differed by strain. Median duration of symptoms was longer in cases of Flu B compared to Flu A (3.0 v 1.9 days; p=0.006), however antibiotics was much less often prescribed for these individuals (8% versus 42%; p=0.001).   Differences in vaccination history were found, as Flu B cases were less likely to have received Flu vaccination in 2010 than cases of Flu A (16% vs 36%; p=0.046).  Individuals with 2009 H1N1 were older on average (51 vs 39 yrs; p<0.001), had significantly lower rates of diabetes (12% vs 28%; p=0.006), but were more likely to be intubated (5% vs 0%, p<0.001) than individuals with other types of Flu. All the six patients who died during the past season were diagnosed with 2009 H1N1.

Conclusion:2009 H1N1 is still the most deadly and prevalent strain circulating in Southeast Michigan. Based on these findings, strain specific testing is warranted in the upcoming season.


Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

Odaliz Abreu-Lanfranco, MD1, Dror Marchaim, MD2, Varinia Urday-Cornejo3, Christopher C. Cooper, BS4, Mohan Babu, MBBS5, Geetha Manikonda, MBBS5, Kayoko Hayakawa, MD, PhD4, Teena Chopra, MD6, Sorabh Dhar, MD6, Paul Lephart, PhD2, George Alangaden, MD6, Keith Kaye, MD, MPH, FIDSA7 and Emily Martin, MPH, PhD8, (1)Division of ID, 5 Hudson, Wayne State University, Detroit Medical Center, Detroit, MI, (2)Detroit Medical Center (DMC) / Wayne State University, Detroit, MI, (3)Infectious Diseases, Wayne State University, Detroit , MI, (4)Detroit Medical Center / Wayne State University, Detroit, MI, (5)Wayne State University/Detroit Medical Center, Detroit, MI, (6)Detroit Medical Center/Wayne State University, Detroit, MI, (7)Detroit Medical Center, Detroit, MI, (8)Pharmacy Practice, Wayne State University, Detroit, MI

Disclosures:

O. Abreu-Lanfranco, None

D. Marchaim, None

V. Urday-Cornejo, None

C. C. Cooper, None

M. Babu, None

G. Manikonda, None

K. Hayakawa, None

T. Chopra, None

S. Dhar, None

P. Lephart, None

G. Alangaden, None

K. Kaye, None

E. Martin, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.