Search

Outbreaks of acute haemorrhagic conjunctivitis (AHC) - a rapidly progressing and highly contagious infection - often occur in schools during summer and autumn. We used dynamic modelling to evaluate the efficacy of interventions to control AHC outbreaks in schools. A susceptible-infected-recovered (SIR) model was built to simulate AHC outbreaks in Chinese schools, with isolation or school closure added into the model. We used outbreak data from the period 2004-2015 in our models to estimate the effective reproduction number and assess the efficacy of interventions. The median effective reproduction number (uncontrolled) of AHC outbreaks was 7·00 (range 1·77-25·87). The median effective reproduction number (controlled) of AHC outbreaks was 0·16 (range 0·00-2·28). Intervention efficacy is affected by the timing of isolation; earlier isolation is associated with a lower morbidity peak and smaller total attack rate (TAR). School closures were not effective; TARs were almost 100% and did not change even when different school closure durations were adopted. Isolation and school closure as a combined intervention strategy was used to simulate outbreak control, but the efficacy was the same as isolation alone. An isolation programme could be an effective primary intervention during AHC outbreaks in schools. However, school closure is not recommended.

To assess the efficacy of quarantine for acute hemorrhagic conjunctivitis (AHC) outbreaks control in schools, by using the Compartment Model. Through combining the characters of both AHC and compartment model, we built a susceptive-infective-removal (SIR) model suited for AHC outbreaks control in schools, and then quarantine was added into the model to develop a susceptive-infective-quarantine-removal (SIQR) model. An outbreak of AHC in Changsha in 2011 was employed as a sample to assess the effect of quarantine for the prevention and control of AHC. Basic reproduction number (λ0) of the AHC outbreak without intervention was 6.80, thus the transmission speed of the disease became quite fast. If no intervention had been adopted, almost all the students, faculties and staff members would have been infected within 23 days, and the accumulative cases would become 738, with the total attack rate (TAR) as 99.73%. The peak of the outbreak was at Sep. 11th and the number of new cases was 126 on that day. The efficacy would have been different if quarantine forces had been taken at different time and differently. The bigger and earlier the quarantine force had been adopted, the lower morbidity peak and the smaller TAR would have been appeared, with better efficacy of outbreak control. If the quarantine rate had been taken at the level of 90% on the sixth day, the accumulative case would have been reduced to 132 and the TAR had become 17.84% consequently. Quarantine program could be used as a main intervention approach to be employed for ACH outbreak at schools.

To simulate intervention measures in controlling an outbreak of acute hemorrhagic conjunctivitis on one school campus by using the Susceptible-Infected-Recovered (SIR) model, to provide evidence for preparedness and response to the epidemic. Classical SIR model was used to model the epidemic. Malthusian exponential decline method was employed to estimate the infective coefficient β for interventions. The initial value of parameters was determined based on empirical data. The modeling was implemented using Matlab 7.1 software. Without interventions, the outbreak was expected to experience three phrases: (1) early stage (the first 5 days) in which the epidemic developed slowly and could be intervened easily; (2) rapid growing stage (6 - 15 days) in which the number of infected cases increased quickly and the epidemic could not be well controlled; and (3) medium and late stage (16 days and later) in which more than 90% of the susceptible persons were infected but the intervention measures failed to prevent the epidemic. With the implementation of interventions, the epidemic was predicted to be controlled in the early stage, under the SIR model. The simulation based on the SIR model kept an acceptable consistency with the actual development of epidemic after the implementation of intervention measures. The SIR model seemed effective in modeling interventions to the epidemic of acute hemorrhagic conjunctivitis in the schools.