The Promise of Saliva-Based Diagnostics for Monkeypox Outbreak Response
The recent global outbreak of monkeypox has underscored the urgent need for improved diagnostic capabilities that can support rapid case identification and effective disease surveillance. Current recommendations for the diagnosis of monkeypox rely on lesion-swabs as the gold-standard specimen type, despite many patients experiencing symptoms prior to the appearance of the characteristic skin lesions. Alternative sample types, such as saliva, which enable earlier detection could bolster the monkeypox response by mitigating transmission and facilitating timely access to antiviral treatments.
Saliva Emerges as a Viable Option for Monkeypox Diagnosis
Over the past year, a growing body of evidence has highlighted the potential of saliva as a diagnostic specimen for the detection of monkeypox virus. Several studies have reported high concordance between saliva and lesion-swab samples, with some cases identified through saliva testing that did not present with visible skin lesions. Notably, saliva has demonstrated the ability to detect the virus earlier in the course of infection, as viral loads often peak in saliva before reaching their highest levels in lesion samples.
These findings underscore the key advantages that saliva-based testing could offer for monkeypox outbreak response and ongoing disease surveillance efforts. Saliva is a non-invasive sample type that can be self-collected, reducing the burden on healthcare workers and enabling more frequent sample collection from exposed individuals. This, in turn, facilitates earlier case identification and isolation – critical steps for halting transmission chains. Furthermore, the ease and comfort of saliva collection holds particular promise for expanding access to testing, especially in resource-limited settings where the current reliance on specialized swabs and personal protective equipment poses significant logistical challenges.
Adapting an Extraction-Free, Saliva-Based PCR Test for Monkeypox Detection
Recognizing the potential of saliva-based diagnostics to strengthen the response to the ongoing monkeypox outbreak, our team sought to adapt our previously developed SalivaDirect protocol – an open-source, extraction-free PCR test for SARS-CoV-2 – for the detection of monkeypox virus. By leveraging this streamlined approach, we aimed to create a flexible, low-cost testing solution that could be readily deployed to support sustainable disease surveillance and outbreak control efforts.
Evaluating Monkeypox PCR Assay Performance in Saliva Samples
We first compared the performance of five different PCR assays for the detection of monkeypox virus in 30 saliva samples collected using the Spectrum SDNA-1000 collection device. Despite identifying several nucleotide substitutions in the primers of the CDC’s Monkeypox Virus Generic Real-Time PCR Test, we observed no significant differences in the mean cycle threshold (Ct) values generated across the assays.
Importantly, we were able to successfully incorporate each of the five PCR assays into our extraction-free, saliva-based testing workflow. This flexibility is crucial, as it allows laboratories to leverage assays that have been recommended or validated by regulatory authorities, while maintaining the benefits of a simplified, low-cost testing approach.
Evaluating Monkeypox Stability in Raw Saliva Samples
To further explore the feasibility of saliva-based testing for monkeypox, we investigated the stability of viral detection in raw, unsupplemented saliva samples. We found that the presence of monkeypox virus DNA remained relatively stable for 24-48 hours when stored at temperatures ranging from 4°C to 30°C. Even at the higher temperature of 40°C, detection was maintained for the first 24 hours before declining.
Importantly, monkeypox detection also remained stable when the saliva samples were subjected to simulated shipping conditions, representing both summer and winter temperature profiles. These findings suggest that saliva samples could potentially be transported through postal systems without the need for specialized cold chain logistics, further reducing the barriers to widespread testing access.
Implications for Improving Monkeypox Outbreak Response and Surveillance
The results of this pilot study highlight the promise of a flexible, saliva-based, extraction-free PCR test for the detection of monkeypox virus. By leveraging the advantages of saliva as a specimen type and the simplicity of our streamlined testing approach, this solution has the potential to significantly enhance outbreak response and strengthen sustainable disease surveillance efforts, particularly in resource-limited settings.
Facilitating Earlier Case Identification and Isolation
The ability to detect monkeypox virus in saliva prior to the appearance of characteristic skin lesions could enable earlier case identification and isolation, crucial steps for halting transmission chains. By collecting serial saliva samples from exposed individuals, public health workers may be able to detect infections earlier, facilitating timely access to antiviral treatments and reducing the window of potential infectiousness.
Expanding Access to Testing
The low-cost and easy-to-implement nature of our saliva-based PCR test could help to address the significant barriers to testing access that have hampered the global response to the monkeypox outbreak. The elimination of specialized swabs and the reduced need for personal protective equipment makes this approach particularly well-suited for deployment in resource-constrained communities, where the current reliance on lesion-swab samples has posed major logistical challenges.
Supporting Sustainable Surveillance
Beyond outbreak response, the stability of monkeypox detection in raw saliva samples under various storage conditions suggests that this testing approach could also support sustainable disease surveillance efforts. The ability to collect and transport samples without the need for specialized cold chain infrastructure could facilitate the establishment of continuous monitoring programs, enabling public health authorities to track the circulation of the virus and rapidly identify emerging threats.
Conclusion
The ongoing global monkeypox outbreak has underscored the urgent need for improved diagnostic tools that can support effective outbreak response and long-term disease surveillance. The findings of this pilot study demonstrate the potential of a flexible, saliva-based, extraction-free PCR test to address these critical gaps.
By enabling earlier case identification, expanding access to testing, and facilitating sustainable surveillance, this innovative approach could play a vital role in strengthening the global public health community’s ability to mitigate the impact of monkeypox and prepare for future emerging infectious disease threats. As we continue to navigate the evolving landscape of monkeypox, the development and deployment of flexible, low-cost diagnostic solutions like this will be essential for protecting vulnerable communities and safeguarding global health security.
