Skip to main content Accessibility help

Duration of Influenza A Virus Shedding in Hospitalized Patients and Implications for Infection Control

  • Surbhi Leekha (a1), Nicole L. Zitterkopf (a2), Mark J. Espy (a2), Thomas F. Smith (a2), Rodney L. Thompson (a3) and Priya Sampathkumar (a3)...



To assess the duration of shedding of influenza A virus detected by polymerase chain reaction (PCR) and cell culture among patients hospitalized with influenza A virus infection.


Mayo Clinic (Rochester, Minnesota) hospitals that cater to both the community and referral populations.


Patients 18 years old and older who were hospitalized between December 1, 2004, and March 15, 2005, with a laboratory-confirmed (ie, PCR-based) diagnosis of influenza A virus infection were consecutively enrolled. Additional throat swab specimens were collected at 2, 3, 5, and 7 days after the initial specimen (if the patient was still hospitalized). All specimens were tested by PCR and culture (both conventional tube culture and shell vial assay). Information on demographic characteristics, date of symptom onset, comorbidities, immunosuppression, influenza vaccination status, and receipt of antiviral treatment was obtained by interview and medical record review. Patients were excluded if informed consent could not be obtained or if the date of symptom onset could not be ascertained.


Of 149 patients hospitalized with influenza A virus infection, 50 patients were enrolled in the study. Most patients were older (median age, 76 years), and almost all (96%) had underlying chronic medical conditions. Of 41 patients included in the final analysis, influenza A virus was detected in 22 (54%) by PCR and in 12 (29%) by culture methods at or beyond 7 days after symptom onset. All 12 patients identified by culture also had PCR results positive for influenza A virus.


Hospitalized patients with influenza A virus infection can shed detectable virus beyond the 5- to 7-day period traditionally considered the duration of infectivity. Additional research is needed to assess whether prolonging the duration of patient isolation is warranted to prevent nosocomial outbreaks during the influenza season.


Corresponding author

Mayo Clinical College of Medicine, 200 First St. SW, Rochester, MN 55905 (


Hide All
1. Harper, SA, Fukuda, K, Uyeki, TM, Cox, NJ, Bridges, CB; Advisory Committee on Immunization Practices (ACIP), Centers for Disease Control and Prevention (CDC). Prevention and control of influenza: recommendations of the Advisory Committee on Immunization practices (ACIP). MMWR Recomm Rep 2005;54(RR-8):140.
2. Talbot, TR, Crocker, DD, Peters, J, et al. Duration of virus shedding after trivalent intranasal live attenuated influenza vaccination in adults. Infect Control Hosp Epidemiol 2005;26:494500.
3. Klimov, AI, Rocha, E, Hayden, FG, Shult, PA, Roumillat, LF, Cox, NJ. Prolonged shedding of amantadine-resistant influenzae A viruses by immunodeficient patients: detection by polymerase chain reaction-restriction analysis. J Infect Dis 1995;172:13521355.
4. Englund, JA, Champlin, RE, Wyde, PR, et al. Common emergence of amantadine- and rimantadine-resistant influenza A viruses in symptomatic immunocompromised adults. Clin Infect Dis 1998;26:14181424.
5. Boivin, G, Goyette, N, Bernatchez, H. Prolonged excretion of amantadine-resistant influenza a virus quasi species after cessation of antiviral therapy in an immunocompromised patient. Clin Infect Dis 2002;34:E23E25.
6. Nichols, WG, Guthrie, KA, Corey, L, Boeckh, M. Influenza infections after hematopoietic stem cell transplantation: risk factors, mortality, and the effect of antiviral therapy. Clin Infect Dis 2004;39:13001306.
7. Frank, AL, Taber, LH, Wells, CR, Wells, JM, Glezen, WP, Paredes, A. Patterns of shedding of myxoviruses and paramyxoviruses in children. J Infect Dis 1981;144:433441.
8. Kiso, M, Mitamura, K, Sakai-Tagawa, Y, et al. Resistant influenza A viruses in children treated with oseltamivir: descriptive study. Lancet 2004;364:759765.
9. Centers for Disease Control and Prevention. Guidelines and recommendations: infection control guidance for the prevention and control of influenza in acute-care facilities, revision 2/8/07. Available at: Accessed March 31, 2007.
10. Tablan, OC, Bridges, C, Hajjeh, R. Guidelines for preventing health-care-associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep 2004;53(RR-3):136.
11. Clements, ML, Betts, RF, Tierney, EL, Murphy, BR. Serum and nasal wash antibodies associated with resistance to experimental challenge with influenza A wild-type virus. J Clin Microbiol 1986;24:157160.
12. Doherty, PC, Topham, DJ, Tripp, RA, Cardin, RD, Brooks, JW, Stevenson, PG. Effector CD4+ and CD8+ T-cell mechanisms in the control of respiratory virus infections. Immunol Rev 1997;159:105117.
13. Goodwin, K, Viboud, C, Simonsen, L. Antibody response to influenza vaccination in the elderly: a quantitative review. Vaccine 2006;24:11591169.
14. Murasko, DM, Bernstein, ED, Gardner, EM, et al. Role of humoral and cell-mediated immunity in protection from influenza disease after immunization of healthy elderly. Exp Gerontol 2002;37:427439.
15. Hebert, PL, McBean, AM, Kane, RL. Explaining trends in hospitalizations for pneumonia and influenza in the elderly. Med Care Res Rev 2005;62:560582.
16. Hayden, FG, Treanor, JJ, Fritz, RS, et al. Use of the oral neuraminidase inhibitor oseltamivir in experimental human influenza: randomized controlled trials for prevention and treatment. JAMA 1999;282:12401246.
17. Sato, M, Hosoya, M, Kato, K, Suzuki, H. Viral shedding in children with influenza virus infections treated with neuraminidase inhibitors. Pediatr Infect Dis J 2005;24:931932.
18. Suzuki, H, Saito, R, Masuda, H, Oshitani, H, Sato, M, Sato, I. Emergence of amantadine-resistant influenza A viruses: epidemiological study. J Infect Chemother 2003;9:195200.
19. Covalciuc, KA, Webb, KH, Carlson, CA. Comparison of four clinical specimen types for detection of influenza A and B viruses by optical immunoassay (FLU OIA test) and cell culture methods. J Clin Microbiol 1999;37:39713974.
20. Pregliasco, F, Mensi, C, Camorali, L, Anselmi, G. Comparison of RT-PCR with other diagnostic assays for rapid detection of influenza viruses. J Med Virol 1998;56:168173.
21. Ruest, A, Michaud, S, Deslandes, S, Frost, EH. Comparison of the Directigen flu A+B test, the QuickVue influenza test, and clinical case definition to viral culture and reverse transcription-PCR for rapid diagnosis of influenza virus infection. J Clin Microbiol 2003;41:34873493.
22. Habib-Bein, NF, Beckwith, WH III Mayo, D, Landry, ML. Comparison of SmartCycler real-time reverse transcription-PCR assay in a public health laboratory with direct immunofluorescence and cell culture assays in a medical center for detection of influenza A virus. J Clin Microbiol 2003;41:35973601.

Related content

Powered by UNSILO

Duration of Influenza A Virus Shedding in Hospitalized Patients and Implications for Infection Control

  • Surbhi Leekha (a1), Nicole L. Zitterkopf (a2), Mark J. Espy (a2), Thomas F. Smith (a2), Rodney L. Thompson (a3) and Priya Sampathkumar (a3)...


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.