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1.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-294995

ABSTRACT

Background: The delta variant of SARS-CoV-2 is now the predominant variant worldwide. However, its transmission dynamics remain unclear. Methods We analyzed all case patients in local clusters and temporal patterns of viral shedding using contact tracing data from 405 cases associated with the delta variant of SARS-CoV-2 between 22 June and 31 July 2021 in Daejeon, South Korea. Results Overall, half of the cases were aged under 19 years, and 20% were asymptomatic at the time of epidemiological investigation. We estimated the mean serial interval as 3.26 days (95% credible interval 2.92, 3.60), and 12% of the transmission occurred before symptom onset of the infector. We identified six clustered outbreaks, and all were associated with indoor facilities. In 23 household contacts, the secondary attack rate was 63% (52/82). We estimated that 15% (95% confidence interval, 13–18%) of cases seeded 80% of all local transmission. Analysis of the nasopharyngeal swab samples identified virus shedding from asymptomatic patients, and the highest viral load was observed two days after symptom onset. The temporal pattern of viral shedding did not differ between children and adults ( P  = 0.48). Conclusions Our findings suggest that the delta variant is highly transmissible in indoor settings and households. Rapid contact tracing, isolation of the asymptomatic contacts, and strict adherence to public health measures are needed to mitigate the community transmission of the delta variant.

2.
J Infect Dis ; 225(5): 793-799, 2022 03 02.
Article in English | MEDLINE | ID: covidwho-1550555

ABSTRACT

BACKGROUND: The Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the predominant variant worldwide at the time of this study. However, its transmission dynamics were unclear. METHODS: We analyzed 405 local cases infected with the Delta variant of SARS-CoV-2 and temporal patterns of viral shedding identified between 22 June and 31 July 2021 in Daejeon, South Korea. RESULTS: Overall, 20% were presymptomatic at the time of epidemiological investigation. We identified 6 clustered outbreaks, and all were associated with indoor facilities. In 23 household contacts, the secondary attack rate was 63%. We estimated the mean serial interval as 3.26 days (95% credible interval, 2.92-3.60), and 15% (95% confidence interval, 13%-18%) of cases seeded 80% of all local transmission. Analysis of the nasopharyngeal swab samples identified virus shedding from the presymptomatic cases and the highest viral load was observed 2 days after symptom onset. CONCLUSIONS: Our findings suggest that the Delta variant is highly transmissible in indoor settings and households. Rapid contact tracing, isolation of the asymptomatic contacts, strict adherence to public health measures, and increased uptake of coronavirus disease 2019 (COVID-19) vaccination, including booster doses, are needed to reduce community transmission of the Delta variant.


Subject(s)
COVID-19/epidemiology , COVID-19/transmission , Communicable Disease Control/methods , SARS-CoV-2 , Adolescent , Adult , Aged , COVID-19/prevention & control , Child , Child, Preschool , Contact Tracing , Disease Outbreaks , Female , Humans , Incidence , Infant , Infant, Newborn , Male , Middle Aged , Republic of Korea/epidemiology , Reverse Transcriptase Polymerase Chain Reaction , SARS-CoV-2/genetics , Virus Shedding
3.
J Am Geriatr Soc ; 69(11): 3044-3050, 2021 11.
Article in English | MEDLINE | ID: covidwho-1398482

ABSTRACT

BACKGROUND: Among nursing home residents, for whom age and frailty can blunt febrile responses to illness, the temperature used to define fever can influence the clinical recognition of COVID-19 symptoms. To assess the potential for differences in the definition of fever to characterize nursing home residents with COVID-19 infections as symptomatic, pre-symptomatic, or asymptomatic, we conducted a retrospective study on a national cohort of Department of Veterans Affairs (VA) Community Living Center (CLC) residents tested for SARS-CoV-2. METHODS: Residents with positive SARS-CoV-2 tests were classified as asymptomatic if they did not experience any symptoms, and as symptomatic or pre-symptomatic if the experienced a fever (>100.4°F) before or following a positive SARS-CoV-2 test, respectively. All-cause 30-day mortality was assessed as was the influence of a lower temperature threshold (>99.0°F) on classification of residents with positive SARS-CoV-2 tests. RESULTS: From March 2020 through November 2020, VA CLCs tested 11,908 residents for SARS-CoV-2 using RT-PCR, with a positivity of rate of 13% (1557). Among residents with positive tests and using >100.4°F, 321 (21%) were symptomatic, 425 (27%) were pre-symptomatic, and 811 (52%) were asymptomatic. All-cause 30-day mortality among residents with symptomatic and pre-symptomatic COVID-19 infections was 24% and 26%, respectively, while those with an asymptomatic infection had mortality rates similar to residents with negative SAR-CoV-2 tests (10% and 5%, respectively). Using >99.0°F would have increased the number of residents categorized as symptomatic at the time of testing from 321 to 773. CONCLUSIONS: All-cause 30-day mortality was similar among VA CLC residents with symptomatic or pre-symptomatic COVID-19 infection, and lower than rates reported in non-VA nursing homes. A lower temperature threshold would increase the number of residents recognized as having symptomatic infection, potentially leading to earlier detection and more rapid implementation of therapeutic interventions and infection prevention and control measures.


Subject(s)
COVID-19 Testing/statistics & numerical data , COVID-19/diagnosis , Fever/diagnosis , Skilled Nursing Facilities , Veterans/statistics & numerical data , Aged , Asymptomatic Infections , COVID-19/complications , Female , Fever/etiology , Humans , Male , Middle Aged , Retrospective Studies
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