After weeks of frustration, commercial testing for monkeypox is now going strong in the US and has reduced the backlog. The tests show that, as of Monday, the US had nearly 3,500 cases, among the most in the world.
Yet wider access to existing tests hasn’t made it possible to diagnose infections before they have a chance to spread. For that, the Centers for Disease Control and Prevention and the Food and Drug Administration need to consider new approaches to testing.
The FDA maintains that monkeypox should be detected only by swabbing the lesions of someone who has a rash. In the early days of this outbreak, that guidance was reasonable. Previous outbreaks in African countries where the disease is endemic suggested that contact with lesions was the primary form of transmission.
But now infections are manifesting differently in vulnerable populations of men who have sex with men. Doctors treating people with monkeypox in the US say patients are coming in with rectal pain or severe sore throat (and testing negative for sexually transmitted infections) but have no skin lesions — yet. Before lesions appear, however, doctors have no CDC-validated way to confirm an infection.
Infectious disease doctors on the frontlines of the monkeypox outbreak would like to be able to test other types of samples — saliva, for example, or throat or rectal swabs, which they are often taking anyway to look for an STI — to possibly detect infections before the rash takes hold. Such sampling also could enable public health officials to cast a wider net, to test anyone in a high-risk group who comes into a clinic, regardless of their symptoms. “If we were to do a lot of those tests, I suspect many will come back positive,” said Abraar Karan, an infectious disease physician at Stanford University.
Another concern: The current strategy assumes that lesions are a proxy for contagiousness when, in reality, not enough is known about the ways in which monkeypox virus might be transmitted. Studies of patients in Italy and Spain show that viral DNA can be detected in nasal swabs, urine, blood, feces, semen and saliva. Using — and studying — alternative kinds of testing might reveal when that viral DNA is shed from the body, and for how long, and under what circumstances it might be passed along to others.
This could not only help identify more cases earlier but also provide monkeypox patients better information about their health. They could get answers to pressing questions such as how long they need to isolate and when they can safely resume sexual activity.
Although the CDC advises patients to remain isolated until their lesions heal, infectious disease doctors would like to understand whether the virus could be passed on through sexual contact for a longer period. Monkeypox viral DNA was found in the semen of 29 out of 32 people in a recent study. Based on other reports of lingering viral DNA in semen, public health authorities in the UK advise recovering patients to use condoms for 12 weeks after their infections.
Meanwhile, testing that could diagnose infections earlier could help prevent people from infecting others before they have visible symptoms. And it could help direct vaccination efforts to close contacts of people early in their infections. The monkeypox vaccine, while still frustratingly limited in supply, can be given after an exposure to prevent a more serious case of the disease.
One testing outfit, Flow Health, is already offering a saliva-based monkeypox test that uses the kind of technology found in widely used Covid spit tests. The company has been collecting data on the accuracy of its test since the first cases of monkeypox started cropping up in the US, and it hopes to soon submit data to the FDA.
A saliva-based test could also make possible at-home sample collection, allowing someone to drop their kit into a mailbox or at a community health site. That could significantly widen access to and uptake of tests, said Jeffrey Klausner, a public health expert at the University of Southern California’s Keck School of Medicine.
The CDC is reportedly considering saliva and other types of tests, but seems be concerned that such tests could produce too many false negatives and thus miss cases. Any alternative testing method would need to be closely studied, it’s true, but cases are already being missed in the US, either for lack of access to tests or lack of lesions in early cases.
The virus has been opportunistic in finding a network in which it can thrive. Public health must in turn be opportunistic in finding the best way to detect and contain the disease.
Bloomberg
