Differences in the Epidemiological Characteristics and Clinical Outcomes of Pandemic (H1N1) 2009 Influenza, Compared with Seasonal Influenza

Abstract

BACKGROUND There are limited data comparing the clinical presentations, comorbidities, and outcomes of patients with infections due to seasonal influenza with patients with infections due to pandemic (H1N1) 2009 influenza. OBJECTIVE To compare the epidemiological characteristics and outcomes of pandemic (H1N1) 2009 influenza with those of seasonal influenza. METHODS A cross-sectional study was conducted among patients who received diagnoses during emergency department and inpatient encounters at 2 affiliated academic medical centers in Philadelphia, Pennsylvania. Cases of seasonal influenza during the period November 1, 2005, through June 1, 2008, and cases of pandemic influenza during the period from May 1, 2009, through August 7, 2009, were identified retrospectively. RESULTS Forty-nine cases of pandemic influenza and 503 cases of seasonal influenza were identified. Patients with pandemic H1N1 were younger (median age, 29 years) than patients with seasonal influenza (median age, 59 years) (P < .001). More patients with pandemic H1N1 (35 [71%] of 49) were African American, compared with patients with seasonal influenza (267 [53%] of 503; P =.02). Several symptoms were more common among patients with pandemic influenza infections than among patients with seasonal influenza infections: cough (98% vs 83%; P =.007), myalgias (71% vs 46%; P =.001), and pleuritic chest pain (45% vs 15%; P < .001). Pregnancy was the only comorbidity that occurred significantly more often in the pandemic influenza group than in the seasonal influenza group (16% vs 1%; P < .001). There were no significant differences in frequencies of deaths of hospitalized patients, intensive care unit admission, or length of hospitalization between groups. CONCLUSION Other than pregnancy, there were few clinically important differences between infections due to seasonal influenza and those due to pandemic influenza. The greater rate of lower respiratory tract symptoms in pandemic cases might serve to differentiate pandemic influenza from seasonal influenza.

Clinical and Epidemiological Profile of Pandemic Influenza A H1N1, H3N2, and Type B in the Southeast of Caspian Sea, Iran

“…Also, Li et al in 2011 in a their study reported that female subjects with influenza A are higher than males (20). Also, this point was reported by other researchers (21)(22)(23). And in Cao et al's study, male subjects were higher, however, Caini et al presented that sexes were equally distributed (15).…”

Rates of Hospital-Acquired Influenza Due to the Pandemic H1N1 Virus in 2009, Compared with Seasonal Influenza

“…To the Editor-As was reported recentiy in the journal by Shiley et al, 1 it is important to investigate the differences in clinical and epidemiological characteristics between pandemic and seasonal influenza. However, is interesting to describe the differences in nosocomial transmission.…”

Characteristics of influenza A (H1N1): Analysis of the cases treated in Clinical centre 'Kragujevac' in Kragujevac

“…Prosečna životna dob bolesnika bila je 29,26 godina i znatno je niža nego u prethodnim sezonama, ali je slična onoj koja se za ovu sezonu navodi u drugim regionima sveta (11)(12)(13)(14). nagli pad broja obolelih starijih od 60 godina života objašnjava se činjenicom da su te osobe tokom svog života (najverovatnije u detinjstvu, 1957. godine), došle u kontakt sa agensom koji je genetski sličan novom virusu gripa, i tom prilikom stvorile zaštitna antitela, koja ih sada štite od infekcije (15).…”

“…iz dostupnih literarnih podataka vidimo da je često ispitivana uloga prethodnih bolesti ili stanja na pojavu težih kliničkih formi gripa koje su zahtevale bolničko lečenje. najviše je ispitivano učešće oboljenja respiratornog sistema, posebno astme, bolesti kardiovaskularnog sistema, dijabetesa, gojaznosti, hronične bolesti srca i imunosupresije (14,(22)(23)(24). u našem ispitivanju, od prisutnih koomorbiditeta kod hospitalizovanih pacijenata registrovane su: bronhijalna astma (7,67%), dijabetes (5,21%), hronične bolesti pluća (4,60%), bolesti kardiovaskularnog sistema (4,29%), bolesti nervnog sistema (3,99%) i karcinomi (0,31%), a neretko je kod iste osobe utvrđeno postojanje i dve bolesti.…”