tetano
Editor, Senior Moderator
J Infect Dis. 2015 Apr 15. pii: jiv225. [Epub ahead of print]
[h=1]Influenza A virus shedding and infectivity in households.[/h] Tsang TK[SUP]1[/SUP], Cowling BJ[SUP]1[/SUP], Fang VJ[SUP]1[/SUP], Chan KH[SUP]2[/SUP], Ip DK[SUP]1[/SUP], Leung GM[SUP]1[/SUP], Peiris JS[SUP]3[/SUP], Cauchemez S[SUP]4[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] [h=4]BACKGROUND:[/h] Viral shedding is often considered to correlate with the infectivity of influenza, while the evidence for this is limited.
[h=4]METHODS:[/h] In a detailed study of influenza virus transmission within households in 2008-12, index cases with confirmed influenza were identified in outpatient clinics, and we collected nose and throat swab specimens for testing by RT-PCR from all household members regardless of illness. We used individual-based hazard models to characterize the relationship between viral load (V) and infectivity.
[h=4]RESULTS:[/h] Assuming infectivity was proportional to viral load V gave the worst fit as it strongly overestimated the proportion of transmission occurring at symptom onset. Alternative models that assumed infectivity was proportional to a various functions of V provided better fits although they all overestimated the proportion of transmission occurring >3 days after symptom onset. The best fitting model assumed infectivity was proportion to V[SUP]γ[/SUP], with estimates of γ=0.136 and γ=0.156 for seasonal influenza A(H1N1) or A(H3N2) respectively.
[h=4]CONCLUSIONS:[/h] All the models we considered that used viral loads to approximate infectivity of a case imperfectly explained the timing of influenza secondary infections in households. Identification of more accurate correlates of infectivity will be important to inform control policies and disease modeling.
? The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
PMID: 25883385 [PubMed - as supplied by publisher]
[h=1]Influenza A virus shedding and infectivity in households.[/h] Tsang TK[SUP]1[/SUP], Cowling BJ[SUP]1[/SUP], Fang VJ[SUP]1[/SUP], Chan KH[SUP]2[/SUP], Ip DK[SUP]1[/SUP], Leung GM[SUP]1[/SUP], Peiris JS[SUP]3[/SUP], Cauchemez S[SUP]4[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] [h=4]BACKGROUND:[/h] Viral shedding is often considered to correlate with the infectivity of influenza, while the evidence for this is limited.
[h=4]METHODS:[/h] In a detailed study of influenza virus transmission within households in 2008-12, index cases with confirmed influenza were identified in outpatient clinics, and we collected nose and throat swab specimens for testing by RT-PCR from all household members regardless of illness. We used individual-based hazard models to characterize the relationship between viral load (V) and infectivity.
[h=4]RESULTS:[/h] Assuming infectivity was proportional to viral load V gave the worst fit as it strongly overestimated the proportion of transmission occurring at symptom onset. Alternative models that assumed infectivity was proportional to a various functions of V provided better fits although they all overestimated the proportion of transmission occurring >3 days after symptom onset. The best fitting model assumed infectivity was proportion to V[SUP]γ[/SUP], with estimates of γ=0.136 and γ=0.156 for seasonal influenza A(H1N1) or A(H3N2) respectively.
[h=4]CONCLUSIONS:[/h] All the models we considered that used viral loads to approximate infectivity of a case imperfectly explained the timing of influenza secondary infections in households. Identification of more accurate correlates of infectivity will be important to inform control policies and disease modeling.
? The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
PMID: 25883385 [PubMed - as supplied by publisher]