Publications by authors named "Amethyst Zhang"
To understand the roles of acute-phase viral dynamics and host immune responses in post-acute sequelae of SARS-CoV-2 infection (PASC), we enrolled 136 participants within 5 days of their first positive SARS-CoV-2 real-time PCR test. Participants self-collected up to 21 nasal specimens within the first 28 days post-symptom onset; interviewer-administered questionnaires and blood samples were collected at enrollment, days 9, 14, 21, 28, and month 4 and 8 post-symptom onset. Defining PASC as the presence of any COVID-associated symptom at their 4-month visit, we compared viral markers (quantity and duration of nasal viral RNA load, infectious viral load, and plasma N-antigen level) and host immune markers (IL-6, IL-10, TNF-α, IFN-α, IFN-γ, MCP, IP-10, and Spike IgG) over the acute period.
View Article and Find Full Text PDFFrom 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.
View Article and Find Full Text PDFBackground: SARS-CoV-2 nucleocapsid antigen can be detected in plasma, but little is known about its performance as a diagnostic test for acute SARS-CoV-2 infection or infectious viral shedding among nonhospitalized individuals.
Methods: We used data generated from anterior nasal and blood samples collected in a longitudinal household cohort of SARS-CoV-2 cases and contacts. Participants were classified as true positives if polymerase chain reaction (PCR) positive for SARS-CoV-2 and as true negatives if PCR negative and seronegative.
Article Synopsis
- The study investigated how vaccination affects the infectiousness of SARS-CoV-2 by comparing viral shedding in unvaccinated and fully vaccinated adults who tested positive for the virus.
- Although maximum RNA levels in both groups were similar, vaccinated individuals showed a quicker decline in viral load and had a shorter duration of infectious virus.
- Specifically, vaccinated participants had a median infectious virus detection duration of 6 days compared to 7.5 days in unvaccinated individuals, showing that vaccination reduces the likelihood of spreading the virus after the first five days of symptoms.
Article Synopsis
- - The emergence of the Omicron variant (B.1.1.529) raised questions about using cycle threshold (Ct) values from RT-PCR tests as indicators of infectiousness for SARS-CoV-2, as low Ct values have been correlated with higher infectiousness in other variants.
- - A study analyzed nasal samples from nonhospitalized individuals in the San Francisco Bay Area, comparing culturable virus presence and Ct values between those infected with pre-Omicron variants and the Omicron BA.1 sublineage.
- - Results indicated that during Omicron BA.1 infections, Ct values were higher (indicating lower viral RNA levels) than in pre-Omicron infections, suggesting that Ct values may not reliably reflect
Background: Households have emerged as important venues for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. Little is known, however, regarding the magnitude and determinants of household transmission in increasingly vaccinated populations.
Methods: From September 2020 to January 2022, symptomatic nonhospitalized individuals with SARS-CoV-2 infection by RNA detection were identified within 5 days of symptom onset; all individuals resided with at least 1 other SARS-CoV-2-uninfected household member.