Unnecessary isolation of mpox can be reduced by adopting test-based protocols

Monkeypox, a disease caused by the monkeypox virus, has seen a significant increase in cases since mid-2022. The 2022 outbreak variant, called clade IIb, has spread globally, primarily affecting men who have sex with men. In response, there has been an increasing need for effective isolation strategies that balance public health and individual freedom.

Using individual data from patients with clade IIb mpox, the dominant clade during the 2022 outbreak in Europe and America, a study led by researchers at Nagoya University in Japan has proposed a sophisticated modeling framework to improve isolation protocols for mpox patients.

Their results show that current standard practice of ending isolation is effective, but implementing test-based protocols can further reduce unnecessary isolation after the infectious period. Their findings, published in Nature Communicationscan improve our response strategies and reduce patient isolation times.

“Our approach emphasizes the crucial role of understanding individual variations in viral shedding dynamics to minimize both the risk of premature isolation termination and unnecessary prolonged isolation,” said Shingo Iwami. “Based on our results, the use of PCR tests can reduce the burden of isolating patients with COPD while preventing further transmission, especially as the number of COPD patients increases.”

The main method of controlling the spread of MPOX is to isolate infected individuals. Current recommendations for isolating patients with MPOX are based on symptoms. The average duration of symptoms is about 3 weeks.

However, the period of MPOX infection varies among patients. Some health officials worry that strategies based on symptoms or fixed time periods cannot account for this variability. As a result, people released into the community may still be contagious.

Iwami and colleagues sought to refine isolation strategies by developing a modeling framework to characterize when infected individuals cease to be infectious, thereby optimizing isolation protocols. They built the models using viral load in lesion samples from previous MPOX studies.

They found that the duration of viral shedding between individuals ranged from 23 to 50 days. The researchers also found greater variation in the duration of viral shedding among cases of mpox that spread across Europe and the United States in 2022.

Using these data, the group compared three isolation strategies: a symptom-based rule where isolation ends when symptoms resolve; a fixed-duration rule where isolation ends after a fixed period, typically three weeks; and a test-based rule where isolation is based on a negative test result with varying numbers and intervals of tests.

Their results showed that the fixed duration rule provided a balance between risk and unnecessary isolation, but was less flexible. In contrast, the test-based rule shortened this period, depending on the number of tests and the intervals. They concluded that while the fixed duration rule was effective, the test-based approach offered a more personalized solution that could better match individuals’ infectious period.

“The test-based rule was shown to be effective in minimizing the risk of prematurely ending isolation and reducing unnecessary isolation time,” Iwami said. “According to our analysis, 63% of individuals in the analyzed population could benefit from reduced isolation periods using the test-based rule compared to symptom-based or fixed-duration rules.”

“To keep the risk of premature release from isolation below 5%, PCR tests optimized by our simulations could reduce isolation periods by more than a week on average compared to the general isolation rule based on the disappearance of symptoms,” he said.

“Our simulations showed that if patients are tested at intervals of 2 to 5 days and get three to four consecutive negative results, we can safely end their isolation,” he continued. “This highlights the limitations of universal isolation policies.”

Implementing a test-based rule requires careful planning and resources, but it could prove more effective in managing the duration of isolation and reducing the burden on isolated individuals. Public health policies could incorporate this knowledge into the design of more flexible and responsive isolation strategies.

By using detailed viral load data and sophisticated modeling, public health authorities can develop more effective isolation protocols that minimize the risk of both premature termination of isolation and unnecessary prolonged isolation.

Iwami said: “Although our study is based on data from clade IIb, if similar data become available for clade Ib, the variant circulating in the current growing epidemic in Africa, we believe the approach of this study would be a useful tool for planning the optimal duration of infection prevention and control.”