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Volume 17, Number 2—February 2011


Characteristics of Patients with Oseltamivir-Resistant Pandemic (H1N1) 2009, United States

Samuel B. Graitcer, Larisa Gubareva, Laurie Kamimoto, Saumil Doshi, Meredith Vandermeer, Janice Louie, Christine Waters, Zack Moore, Katrina Sleeman, Margaret Okomo-Adhiambo, Steven A. Marshall, Kirsten St. George, Chao-Yang Pan, Jennifer M. LaPlante, Alexander Klimov, and Alicia M. FryComments to Author 
Author affiliations: Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (S.B. Gratcer, L. Gubareva, L. Kamimoto, S. Doshi, K. Sleeman, M. Okomo-Adhiambo, A. Klimov, A.M. Fry); Oregon Department of Human Services, Portland, Oregon, USA (M. Vandermeer); California Department of Health, Sacramento, California, USA (J. Louie, C.-Y. Pan); New York State Department of Health, Albany, New York, USA (C. Waters, K. St. George, J.M. LaPlante); North Carolina Department of Health and Human Services, Raleigh, North Carolina, USA (Z. Moore); Wisconsin Department of Health, Madison, Wisconsin, USA (S.A. Marshall)

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Characteristics of patients infected with oseltamivir-resistant and -susceptible pandemic (H1N1) 2009 viruses from national influenza antiviral resistance surveillance and enhanced hospital influenza surveillance, April 2009–June 2010*†

Oseltamivir-resistant infections

Oseltamivir-susceptible infections
Total from national surveillance,
n = 37
Total from FluSurv-NET states,‡ n = 17
National surveillance cases from FluSurv-NET counties, n = 401
National surveillance cases matched in FluSurv-NET, n = 65
Median age, y (range) 18 (1–74) 21 (5–74) 22 (0–89) 31 (0–82)
Female sex
18 (49)
6 (35)

177 (50)
38 (58)
Hospitalized 30 (81) 16 (100) 65 (16) 65 (100)
ICU admission
13/30 (43)
7/12 (58)

14 (23)
Deaths, all cause§
7/31 (23)
2/12 (17)

3 (5)
Oseltamivir exposure¶
31 (89)
16 (94)

6 (14)
Underlying medical condition 33 (89) 17 (100) 49 (75)
Severe/Immunosuppression# 28 (76) 17 (100) 7 (11)**
Pregnancy 1 (2.7) 0 5 (7.7)
Asthma and CLD 10 (27) 2 (18) 21 (34)
CVD 8 (22) 4 (24) 5 (8)
Diabetes mellitus 5 (14) 2 (13) 12 (18)
Chronic kidney disease
4 (11)
3 (19)

5 (8)
No underlying medical conditions
4 (11)

13 (21)
Median time from oseltamivir initiation to specimen collection, d (range) 11 (2–37) 14 (3–37) 1.5 (1–4)††

*Values are no. (%) except as indicated. FluSurv-NET, Influenza Hospitalization Network; ICU, intensive care unit; CLD, chronic lung disease; CVD, cardiovascular disease, excluding hypertension; –, not applicable.
†Missing data were excluded from analysis; denominators are included where they varied from cohort size.
‡Of the 16 oseltamivir-resistant cases from states participating in FluSurv-NET, 5 had county information and were from FluSurv-NET counties. None were high probability matches to a FluSurv-NET hospitalized patient and none were from Oregon. FluSurv-NET captured only 1 hospitalization for each patient infected with pandemic (H1N1) 2009 virus during the year. Repeat hospitalizations were not recorded, although many sites noted repeat hospitalizations for patients with immunosuppressive conditions (L. Kamimoto, pers. comm.).
§Among oseltamivir-resistant cases, 4 deaths were reported to national surveillance as directly caused by influenza. Cause of death was not recorded for patients infected with oseltamivir-susceptible pandemic (H1N1) 2009 virus.
¶Patients with oseltamivir exposure received oseltamivir, either as chemoprophylaxis or treatment, before the collection date of the pandemic (H1N1) 2009 virus specimen tested for antiviral resistance.
#For patients with oseltamivir-resistant pandemic (H1N1) 2009, severe immunosuppression was defined as any of the following: receiving treatment for any cancer within 6 months before onset of influenza illness, currently receiving immunosuppressive medication, including systemic corticosteroids, as part of prevention strategies for transplant (bone marrow or solid organ) rejection, or for management of pulmonary or autoimmune conditions, or having a diagnosis of AIDS, not just HIV infection. For patients within FluSurv-NET, we included any patient with a medical record of the syndromes above or if immunosuppressed or immunosuppression was recorded in the medical chart.
**Among the 7 hospitalized patients from FluSurv-NET with oseltamivir-susceptible pandemic (H1N1) 2009 and an immunosuppressive condition, 3 (43%) were receiving chronic systemic corticosteroids; 1 for systemic lupus erythematosus and the other 2 for unknown reasons. The immunosuppressive condition was not known for 4 patients, but immunosuppression was recorded from the medical record.
††n = 6.

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