PLoS One. 2016 May 6;11(5):e0154418. doi: 10.1371/journal.pone.0154418. eCollection 2016.
Individual Correlates of Infectivity of Influenza A Virus Infections in Households.
Tsang TK1, Fang VJ1, Chan KH2, Ip DK1, Leung GM1, Peiris JS1,3, Cowling BJ1, Cauchemez S4.
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Abstract
BACKGROUND:
Identifying individual correlates of infectivity of influenza virus is important for disease control and prevention. Viral shedding is used as a proxy measure of infectivity in many studies. However, the evidence for this is limited.
METHODS:
In a detailed study of influenza virus transmission within households in 2008-12, we recruited index cases with confirmed influenza infection from outpatient clinics, and followed up their household contacts for 7-10 days to identify secondary infections. We used individual-based hazard models to characterize the relationship between individual viral shedding and individual infectivity.
RESULTS:
We analyzed 386 households with 1147 household contacts. Index cases were separated into 3 groups according to their estimated level of viral shedding at symptom onset. We did not find a statistically significant association of virus shedding with transmission. Index cases in medium and higher viral shedding groups were estimated to have 21% (95% CI: -29%, 113%) and 44% (CI: -16%, 167%) higher infectivity, compared with those in the lower viral shedding group.
CONCLUSIONS:
Individual viral load measured by RT-PCR in the nose and throat was at most weakly correlated with individual infectivity in households. Other correlates of infectivity should be examined in future studies.
PMID: 27153194 [PubMed - in process] Free full text
Individual Correlates of Infectivity of Influenza A Virus Infections in Households.
Tsang TK1, Fang VJ1, Chan KH2, Ip DK1, Leung GM1, Peiris JS1,3, Cowling BJ1, Cauchemez S4.
Author information
Abstract
BACKGROUND:
Identifying individual correlates of infectivity of influenza virus is important for disease control and prevention. Viral shedding is used as a proxy measure of infectivity in many studies. However, the evidence for this is limited.
METHODS:
In a detailed study of influenza virus transmission within households in 2008-12, we recruited index cases with confirmed influenza infection from outpatient clinics, and followed up their household contacts for 7-10 days to identify secondary infections. We used individual-based hazard models to characterize the relationship between individual viral shedding and individual infectivity.
RESULTS:
We analyzed 386 households with 1147 household contacts. Index cases were separated into 3 groups according to their estimated level of viral shedding at symptom onset. We did not find a statistically significant association of virus shedding with transmission. Index cases in medium and higher viral shedding groups were estimated to have 21% (95% CI: -29%, 113%) and 44% (CI: -16%, 167%) higher infectivity, compared with those in the lower viral shedding group.
CONCLUSIONS:
Individual viral load measured by RT-PCR in the nose and throat was at most weakly correlated with individual infectivity in households. Other correlates of infectivity should be examined in future studies.
PMID: 27153194 [PubMed - in process] Free full text