Association of Culturable-Virus Detection and Household Transmission of SARS-CoV-2, California and Tennessee, 2020-2022

From 2 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) household transmission studies (enrolling April 2020 to January 2022) with rapid enrollment and specimen collection for 14 days, 61% (43/70) of primary cases had culturable virus detected ≥6 days post-onset. Risk of secondary infection among household contacts tended to be greater when primary cases had culturable virus detected after onset. Regardless of duration of culturable virus, most secondary infections (70%, 28/40) had serial intervals <6 days, suggesting early transmission. These data examine viral culture as a proxy for infectiousness, reaffirm the need for rapid control measures after infection, and highlight the potential for prolonged infectiousness (≥6 days) in many individuals.

Impact of age and symptom development on SARS-CoV-2 transmission in households with children—Maryland, New York, and Utah, August 2020–October 2021

Background

Households are common places for spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We investigated factors associated with household transmission and acquisition of SARS-CoV-2.

Methods

Households with children ages &lt;18 years were enrolled into prospective, longitudinal cohorts and followed August 2020─August 2021 in Utah, September 2020─August 2021 in New York City, and November 2020─October 2021 in Maryland. Participants self-collected nasal swabs weekly and with onset of acute illness. Swabs were tested for SARS-CoV-2 using reverse-transcription polymerase chain reaction. We assessed factors associated with SARS-CoV-2 acquisition using a multi-level logistic regression adjusted for household size and clustering and SARS-CoV-2 transmission using a logistic regression adjusted for household size.

Results

Among 2,053 people (513 households) enrolled, 180 people (8.8%; in 76 households) tested positive for SARS-CoV-2. Compared to children &lt;12y, odds of acquiring infection were lower for adults ≥18y (adjusted odds ratio[aOR]:0.34, 95% confidence interval[CI]:0.14–0.87); however, this may reflect vaccination status, which protected against SARS-CoV-2 acquisition (aOR:0.17, 95%CI:0.03–0.91). Odds of onward transmission was similar between symptomatic and asymptomatic primary cases (aOR:1.00, 95%CI:0.35–2.93) and did not differ by age (12–17vs. &lt; 12y aOR:1.08, 95%CI:0.20–5.62; ≥18vs. &lt; 12y aOR:1.70, 95%CI:0.52–5.83).

Conclusions

Adults had lower odds of acquiring SARS-CoV-2 compared to children, but this association might be influenced by COVID-19 vaccination, which was primarily available for adults and protective against infection. In contrast, all ages, regardless of symptoms and COVID-19 vaccination, had similar odds of transmitting SARS-CoV-2. Findings underscore the importance of SARS-CoV-2 mitigation measures for persons of all ages.

Household Transmission and Clinical Features of SARS-CoV-2 Infections

OBJECTIVES

Examine age differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission risk from primary cases and infection risk among household contacts and symptoms among those with SARS-CoV-2 infection.

METHODS

People with SARS-CoV-2 infection in Nashville, Tennessee and central and western Wisconsin and their household contacts were followed daily for 14 days to ascertain symptoms and secondary transmission events. Households were enrolled between April 2020 and April 2021. Secondary infection risks (SIR) by age of the primary case and contacts were estimated using generalized estimating equations.

RESULTS

The 226 primary cases were followed by 198 (49%) secondary SARS-CoV-2 infections among 404 household contacts. Age group-specific SIR among contacts ranged from 36% to 53%, with no differences by age. SIR was lower in primary cases age 12 to 17 years than from primary cases 18 to 49 years (risk ratio [RR] 0.42; 95% confidence interval [CI] 0.19-0.91). SIR was 55% and 45%, respectively, among primary case-contact pairs in the same versus different age group (RR 1.47; 95% CI 0.98-2.22). SIR was highest among primary case-contact pairs age ≥65 years (76%) and 5 to 11 years (69%). Among secondary SARS-CoV-2 infections, 19% were asymptomatic; there was no difference in the frequency of asymptomatic infections by age group.

CONCLUSIONS

Both children and adults can transmit and are susceptible to SARS-CoV-2 infection. SIR did not vary by age, but further research is needed to understand age-related differences in probability of transmission from primary cases by age.

Household Transmission and Clinical Features of SARS-CoV-2 Infections by Age in 2 US Communities

OBJECTIVES.

Examine age differences in SARS-CoV-2 transmission risk from primary cases and infection risk among household contacts, and symptoms among those with SARS-CoV-2 infection.

METHODS.

People with SARS-CoV-2 infection in Nashville, Tennessee and central and western Wisconsin and their household contacts were followed daily for 14 days to ascertain symptoms and secondary transmission events. Households were enrolled between April 2020 and April 2021. Secondary infection risks (SIR) by age of the primary case and contacts were estimated using generalized estimating equations.

RESULTS.

The 226 primary cases were followed by 198 (49%) secondary SARS-CoV-2 infections among 404 household contacts. Age group-specific SIR among contacts ranged from 36% to 53%, with no differences by age. SIR was lower from primary cases aged 12–17 years than from primary cases 18–49 years (risk ratio [RR] 0.42; 95% confidence interval [CI] 0.19–0.91). SIR was 55% and 45%, respectively, among primary case-contact pairs in the same versus different age group (RR 1.47; 95% CI 0.98–2.22). SIR was highest among primary case-contacts pairs aged ≥65 years (76%) and 5–11 years (69%). Among secondary SARS-CoV-2 infections, 19% were asymptomatic; there was no difference in the frequency of asymptomatic infections by age group.

CONCLUSIONS.

Both children and adults can transmit and are susceptible to SARS-CoV-2 infection. SIR did not vary by age, but further research is needed to understand age-related differences in probability of transmission from primary cases by age.