A research group from Nagoya University, the Dutch National Institute for Public Health and the Environment, and Ehime University has developed a new simulator for determining the timing of ending isolation for people infected with Empox (clade II).
Empox is an infectious disease caused by the Empox virus, classified into the Congo Basin type (clade I) and the West African type (clade II). Since May 2022, a new clade II lineage has spread to an international epidemic, mainly in Western countries, and the World Health Organization (WHO) has declared a "Public Health Emergency of International Concern (PHEIC)". After that, the number of clade I infections increased and spread mainly in the Democratic Republic of the Congo, and a PHEIC was declared again on August 5, 2024.
Currently, the US Centers for Disease Control and Prevention (CDC) recommends that people infected with EMPO be quarantined for approximately three weeks, but depending on the infectious period of the case, the quarantine may end too early or unnecessarily late. Therefore, in this study, we developed a simulator to verify the timing of terminating quarantine and examined the effectiveness of three different quarantine termination rules: a fixed-period rule (terminating quarantine after a certain period of time), a PCR test-based rule (terminating quarantine after a set number of negative test results), and a symptom-based rule (terminating quarantine after the disappearance of symptoms).
As a result, it was found that the current fixed period rule of about three weeks can prevent over 3% of transmission and is considered to be reasonable. However, it was found that the infectious period for each individual varies widely from 95 to 23 days, and it was shown that isolation based on PCR testing optimized by the simulator can reduce the risk of early isolation termination (the risk of terminating isolation while maintaining infectiousness to others) to less than 50%, while reducing the isolation period by more than one week compared to symptom-based isolation termination.
This study may suggest flexible quarantine strategies that reduce risk while taking into account fluctuating infectivity. In addition, although this study is a study result on clade II, it is possible that important insights can be gained for clade I using similar data sets.
Paper information:[Nature Communications] Modeling the effectiveness of an isolation strategy for managing mpox outbreaks with variable infectiousness profiles
