Study Study design Results
Hsieh et al., 2005 29
Retrospective cohort study
Onset-to-diagnosis: significantly shorter in quarantined individuals (1·20 vs. 2·89 days, p=0·006) Diagnosis-to-classification: numerically shorter in quarantined individuals (6·21 vs. 7·34 days, p=0·7864) Onset-to-diagnosis time from period 1 to periods 2 and 3: significantly longer for period 1 (no intervention measures implemented) than period 2 (interventions include the implementation of a level B quarantine) (3·64 vs. 2·10 days, p<0·0001); no significant difference between periods 2 and 3 (expedited classification procedures in place) (2·10 vs. 2·60 days, p=0·072) Diagnosis-to-classification time from period 1 to periods 2 and 3: no statistically significant difference between periods 1 and 2 (9·18 vs. 8·24 days); the time from period 2 to period 3 was significantly shortened (8·24 vs. 5·65 days, p<0·001)
Pang et al., 2003 26
Retrospective cohort study
Overall attack rate for becoming a probable case among close contacts: 6·3% (95% CI, 5·3–7·3) Attack rate by demographics in % (95% CI): Work or school 0·36 (0–0·77) Household member (nonspouse) 8·8 (6·6–11·0) Spouse 15·4 (11·5–19·2) Nonhousehold relative 11·6 (7·1–16·2) Friend 10·0 (0·70–19·3) Health care worker 0 (0–12·0) Other 0·75 (0–2·2) Among 206 close contacts whose last contact with a patient with SARS was before the patient’s symptom onset; 4 (1·9%) developed SARS. Some interventions, such as the quarantine of low-risk contacts and fever checks at transportation sites, seemed to have less direct impact in curbing the outbreak.
Park et al., 2020 27
Prospective cohort study
MERS infection: 0% in all groups Overall survival rate: 104/116 (90% survived 2 years); no statistically significant difference between groups (p=0·849)
Wang et al., 2007 28
Retrospective cohort study
Advanced age (>60 years) was identified as a risk factor for SARS in both level A and level B quarantine. For level A quarantine, the odds ratio for developing SARS in this age group was 2·7; for level B quarantine, the odds ratio was 10·5. The probabilities for contracting SARS for the referent group (age <20 years) were different (0·09% vs. 0·02% for level A vs. level B quarantine). Quarantining only those with known SARS exposure could have reduced the number of persons quarantined by approximately 64%
Study Type of model used Results
Becker et al., 2005 30
Transmission model
Adopting multiple intervention strategies reduces the reproduction number. Quarantine combined with contact tracing reduces the reproduction number from its base value of 6 to below 1 when cases are diagnosed within about 5 days of the onset of infectivity.
Chau et al., 2003 31 Back-projection method Quarantining the contacts of confirmed and suspected SARS cases seems to be more effective than quarantining only the contacts of confirmed cases due to the diagnosis time lag.
Day et al., 2006 32
Probabilistic models
When isolation is ineffective, the use of quarantine will be most beneficial when there is significant asymptomatic transmission, and if the asymptomatic period is neither very long nor very short. Provided that isolation is effective, the number of infections averted through the use of quarantine is expected to be very low.
Fraser et al., 2004 33 Mathematical model of infectious disease outbreak dynamics SARS and smallpox are easier to control than pandemic influenza and HIV using simple public health measures (i.e., isolation and quarantine).
Gumel et al., 2004 34 Deterministic model Both isolation and quarantine seem to be effective means for controlling the spread of SARS. Reduction of the time to quarantine or isolation resulted in the greatest reduction of cumulative deaths. If limited resources are available, the authors recommend investing all resources in 1 intervention rather than partially investing in both.
Gupta et al., 2005 35
Mathematical and health economic model
The results indicate that quarantine is effective in containing newly emerging infectious diseases and is also cost saving when compared to not implementing a widespread containment mechanism. Primary wave: Infected=1, Quarantined=100, Averted Infections=4,672 Secondary wave: Infected=8, Quarantined=900, Averted Infections=4,608 Tertiary wave: Infected=64, Quarantined=7,400, Averted Infections=4,096
Hsieh et al., 2007 36
Susceptible–infective–recovered model with additional compartments for Level A and Level B quarantine
Level A quarantine prevented approximately 461 additional SARS cases and 62 additional deaths. The effect of a Level B quarantine was comparatively minor; quarantined cases prevented 29 additional cases and 5 deaths. The combined impact of the 2 quarantine levels reduced the case number and deaths by almost half.
Lloyd-Smith et al., 2003 37
Stochastic model
Contact tracing and quarantine can, to some extent, compensate for inadequate isolation facilities, making an increasingly significant contribution as the basic reproductive number rises. If contact tracing is delayed such that no individuals are quarantined until 5 days following exposure, the quarantine’s contribution is considerably reduced. Delays in initiating quarantine or isolation undermine the effectiveness of other control measures, particularly in high-transmission settings. Health care workers are exposed to a prevalence much higher than that in the community-at-large. Measures that reduce transmission within hospitals have the greatest impact on the epidemic’s reproductive number.
Mubayi et al., 2010 38 Dynamic model, cost-effectiveness model The selection of the “best” weighted quarantine and isolation approaches depends on the ability to identify (in a timely fashion) key epidemiological factors such as infectiousness or susceptibility and, of course, resource availability. The authors concluded that increases in the quarantine rates have the same qualitative effect (but different quantitative effects) on each random tracing strategy, and that the total numbers of new cases, deaths, and time to extinction decrease monotonically.
Nishiura et al., 2004 39 Deterministic mathematical model The possible trajectories of a SARS epidemic depends on the levels of public health interventions, as quarantine and precautionary measures greatly affect the transmissibility. There exist intervention threshold levels to lessen the SARS epidemic, and improved, effective interventions can lead to dramatic decreases in its incidence.
Peak et al., 2017 40 Agent-based branching model The interventions are not equivalent, and the choice of which intervention to implement to achieve optimal control depends on the infectious disease’s natural history, its inherent transmissibility, and the intervention feasibility in the particular healthcare setting. The benefit of quarantine over symptom monitoring is maximized for fast-course diseases (short duration of infectiousness and a short latent period compared with the incubation period) and in settings where isolation is highly effective, a large proportion of contacts is traced, or there is a long delay between symptom onset and isolation.
Pourbohloul et al., 2005 41 Urban contact network model For a mildly contagious disease, an outbreak can be controlled with a combination of isolation, which reduces the infectious period by 25%, and quarantine, which successfully sequesters 30% of all case-patient contacts. Much more rigorous isolation and quarantine are required for a highly contagious disease.
Wang, Ruan, 2004 42
General, deterministic model simplified to a two-compartment suspect-probable model and a single-compartment probable model
The incidence rate is characterized by two stages. The first stage is the process of developing protection measures and quarantine policy, and the second stage coincides with the process of maintaining control measures. The study showed the necessity of implementing maximal control measures in the second stage for a certain period to eradicate the disease. Furthermore, the control measures in the second stage should be implemented before a threshold for the number of probable cases is reached.
Wen-Tao et al., 2020 45 Susceptible–infected–recovered model Under weak prevention and control measures that only succeed in reducing the contact rate and infection efficiency by 45% or less the authors predict 4,719 cases with 739 deaths within three months out of 11·5 million inhabitants in Wuhan. Under strong prevention and control measures (defined as measures that succeed to reduce contact rate and infection efficiency by 50% or more) the number of infected people would be about 3,088 and the death toll about 443.
Yip et al., 2007 43 Back-projection method The overall downward trend of the infection curve corresponds well to the date when changes in the review and classification procedure were implemented by the SARS Prevention and Extrication Committee. In the case of a newly emerging infectious disease epidemic, quick identification and isolation of patients with actual and highly probable cases in a single hospital ward is essential to control the epidemic and prevent the spread of infection in the hospital.
Yue et al., 2020 46 Dynamic infectious disease model The authors assume a worsening of the epidemic’s severity if the government relaxes control measures (e.g., allow travelling), while the situation can be controlled by putting strict control measures in place such as the close down in Wuhan.
Zhang et al., 2017 44 Transmission dynamics mode Quarantining close contacts and informing the public of the actual outbreak situation could be the main countermeasures.