Data from: Individual correlates of infectivity of influenza A virus infections in households

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.