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Kwok-Yung Yuen, MD
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From the Carol Yu Centre for Infection and Division of Infectious Diseases, Department of Microbiology, The University of Hong Kong, Queen Mary Hospital.

Correspondence to: Kwok-Yung Yuen, MD, Carol Yu Centre for Infection and Division of Infectious Diseases, Department of Microbiology, The University of Hong Kong, 4/F University Pathology Bldg, 102 Pokfulam Rd, Queen Mary Hospital, Hong Kong; e-mail: kyyuen@hkucc.hku.hk


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.org/site/misc/reprints.xhtml).


© 2010 American College of Chest Physicians


Chest. 2010;138(2):457-458. doi:10.1378/chest.10-1162
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To the Editor:

Oseltamivir has been shown to be efficacious in the treatment of pandemic 2009 influenza A(H1N1) virus [A(H1N1)]-infected patients with mild disease1; a significantly lower viral load at day 5 after symptom onset was achieved as compared with nontreated patients.2 Moreover, a greater rate of viral load reduction in the nasopharyngeal aspirate (NPA) of patients treated with oseltamivir was observed when initiated < 2 days after symptom onset.2 However, the effectiveness and safety of oseltamivir in treating A(H1N1)-infected children aged < 1 year was uncertain; therefore, these patients were excluded from the treated and nontreated groups in our study despite the authorized use of oseltamivir during the pandemic in Europe and a number of other countries.3 Several studies are being performed to address these issues.3 Nevertheless, the age range of nontreated patients in our study was 5 to 49 years; at least one-fourth (7/27) and 77.8% (21/27) were aged ≤ 12 and ≤ 18 years, respectively (unpublished data).2

The respiratory specimens of our study were collected at the beginning of the pandemic when a randomized controlled treatment trial was not feasible because of the uncertainties of disease severity and international recommendations on oseltamivir treatment.2 The viral load of NPA from nontreated patients could only be compared with treated patients with reference to the interval postsymptom onset. The timing of when the first NPA of each patient could be obtained largely depended on their number of days postsymptom onset at presentation, so different numbers of specimens were included at different intervals of postsymptom onset for analysis even when serial samplings were obtained from patients. Some refused further nasopharyngeal sampling once their symptoms improved.2

Thirty-seven percent and 9% of A(H1N1)-infected, oseltamivir-treated patients had virus detected by real-time polymerase chain reaction (PCR) in nasal-throat swabs on days 7 and 10 of illness.4 Similarly, virus was detected in NPA from nontreated and treated patients at days 8 to 9 postsymptom onset (mean viral load, 3.42 ± 1.07 vs 3.51 ± 1.19 log10 copies/mL, P = .937) (unpublished data).2 Young children shed seasonal influenza virus for longer duration than adults.5 Similarly, 50% and 38% of nasopharyngeal swabs from children aged 0 to 9 years had A(H1N1) detected by A(H1N1) PCR at days 8 and 11 postsymptom onset, respectively, whereas only 42% and 20% from adults aged ≥ 18 had virus detected correspondingly.5 None of the PCR-positive specimens collected at day 11 postsymptom onset from patients of all age groups had positive virus culture.5

To KK, Chan KH, Li IW, et al. Viral load in patients infected with pandemic H1N1 2009 influenza A virus. J Med Virol. 2010;821:1-7. [CrossRef] [PubMed]
 
Li IW, Hung IF, To KK, et al. The natural viral load profile of patients with pandemic 2009 influenza A(H1N1) and the effect of oseltamivir treatment. Chest. 2010;1374:759-768. [CrossRef] [PubMed]
 
Reddy D. Responding to pandemic (H1N1) 2009 influenza: the role of oseltamivir. J Antimicrob Chemother. 2010;65suppl 2:ii35-ii40. [CrossRef] [PubMed]
 
Ling LM, Chow AL, Lye DC, et al. Effects of early oseltamivir therapy on viral shedding in 2009 pandemic influenza A (H1N1) virus infection. Clin Infect Dis. 2010;507:963-969. [CrossRef] [PubMed]
 
De Serres G, Rouleau I, Hamelin M-E, et al. Contagious period for pandemic (H1N1) 2009. Emerg Infect Dis. 2010;165:783-788. [CrossRef] [PubMed]
 

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References

To KK, Chan KH, Li IW, et al. Viral load in patients infected with pandemic H1N1 2009 influenza A virus. J Med Virol. 2010;821:1-7. [CrossRef] [PubMed]
 
Li IW, Hung IF, To KK, et al. The natural viral load profile of patients with pandemic 2009 influenza A(H1N1) and the effect of oseltamivir treatment. Chest. 2010;1374:759-768. [CrossRef] [PubMed]
 
Reddy D. Responding to pandemic (H1N1) 2009 influenza: the role of oseltamivir. J Antimicrob Chemother. 2010;65suppl 2:ii35-ii40. [CrossRef] [PubMed]
 
Ling LM, Chow AL, Lye DC, et al. Effects of early oseltamivir therapy on viral shedding in 2009 pandemic influenza A (H1N1) virus infection. Clin Infect Dis. 2010;507:963-969. [CrossRef] [PubMed]
 
De Serres G, Rouleau I, Hamelin M-E, et al. Contagious period for pandemic (H1N1) 2009. Emerg Infect Dis. 2010;165:783-788. [CrossRef] [PubMed]
 
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