Latent and incubation periods of Delta, BA.1, and BA.2 variant cases and associated factors: a cross-sectional study in China.

Publication date: Mar 06, 2024

The latent and incubation periods characterize the transmission of infectious viruses and are the basis for the development of outbreak prevention and control strategies. However, systematic studies on the latent period and associated factors with the incubation period for SAS-CoV-2 variants are still lacking. We inferred the two durations of Delta, BA. 1, and BA. 2 cases and analyzed the associated factors. The Delta, BA. 1, and BA. 2 (and its lineages BA. 2.2 and BA. 2.76) cases with clear transmission chains and infectors from 10 local SAS-CoV-2 epidemics in China were enrolled. The latent and incubation periods were fitted by the Gamma distribution, and associated factors were analyzed using the accelerated failure time model. The mean latent period for 672 Delta, 208 BA. 1, and 677 BA. 2 cases was 4. 40 (95%CI: 4. 24 ~ 4. 63), 2. 50 (95%CI: 2. 27 ~ 2. 76), and 2. 58 (95%CI: 2. 48 ~ 2. 69) days, respectively, with 85. 65% (95%CI: 83. 40 ~ 87. 77%), 97. 80% (95%CI: 96. 35 ~ 98. 89%), and 98. 87% (95%CI: 98. 40 ~ 99. 27%) of them starting to shed viruses within 7 days after exposure. In 405 Delta, 75 BA. 1, and 345 BA. 2 symptomatic cases, the mean latent period was 0. 76, 1. 07, and 0. 79 days shorter than the mean incubation period [5. 04 (95%CI: 4. 83 ~ 5. 33), 3. 42 (95%CI: 3. 00 ~ 3. 89), and 3. 39 (95%CI: 3. 24 ~ 3. 55) days], respectively. No significant difference was observed in the two durations between BA. 1 and BA. 2 cases. After controlling for the sex, clinical severity, vaccination history, number of infectors, the length of exposure window and shedding window, the latent period [Delta: exp(β) = 0. 81, 95%CI: 0. 66 ~ 0. 98, p = 0. 034; Omicron: exp(β) = 0. 82, 95%CI: 0. 71 ~ 0. 94, p = 0. 004] and incubation period [Delta: exp(β) = 0. 69, 95%CI: 0. 55 ~ 0. 86, p 

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Concepts Keywords
China Associated factor
Symptomatic BA.1
Vaccination BA.2
Viruses Delta
Incubation period
Latent period
SARS-CoV-2

Semantics

Type Source Name
disease VO Viruses
disease VO time
disease VO vaccination
disease IDO history
pathway REACTOME Reproduction
disease MESH Infectious Diseases
drug DRUGBANK Coenzyme M
disease VO population
disease MESH COVID 19 pandemic
disease MESH infection
disease IDO symptom
disease IDO host
drug DRUGBANK Ademetionine
disease MESH comorbidity
disease MESH virus shedding
disease VO vaccine
disease VO dose
disease VO unvaccinated
disease VO vaccinated
disease IDO site
disease IDO infectivity
disease IDO immunodeficiency
disease VO vaccine immunization
disease VO effective
disease VO immunized
drug DRUGBANK Carboxyamidotriazole
disease MESH critical illness
disease IDO process
drug DRUGBANK Indoleacetic acid
drug DRUGBANK Etoperidone
disease IDO infectious disease
disease IDO contact tracing
disease IDO virulence
disease IDO intervention
drug DRUGBANK Guanosine
disease IDO facility
disease IDO cell
disease VO CoronaVac
disease IDO replication

Original Article

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