But while a monkeypox test exists, it requires lab workers to do every step by hand, Morice says. Federal guidelines say testing should only be done by cleaning the lesions of a person suspected of having the virus. These lesions look large or blistered and can appear on the face, hands, feet, around the genitals or anus, or inside the mouth or rectum. The assayed samples are then subjected to a PCR (or polymerase chain reaction) test, which involves extracting genetic material and amplifying it to look for the presence of monkeypox virus DNA.
This makes testing slow. Commercial laboratories such as the Mayo Clinic have been working to automate the process of extracting and amplifying viral DNA. Until recently, the clinic could only process 20 to 30 tests using the manual protocol, but soon it will be able to perform several hundred tests a day, Morice says.
This type of test also raises other problems. “Current tests require you to rub an injury. For people with internal injuries, that might not be possible or it’s very painful,” says Makofane.
Another problem is that it cannot be used until a person has visible symptoms, and it can take several days for a rash to appear. Some people may have very subtle or very few lesions. While it’s unclear whether the disease can spread before the blisters form, Rivers says it would be better to catch an infection earlier, so people can access treatment and vaccines as soon as possible. For the best chance of preventing the onset of the disease, the CDC says, the vaccine should be given within four days of the date of exposure.
Like Covid-19 tests in the early days of the pandemic, monkeypox tests must be ordered by a doctor. Morice says many doctors may not know to test for monkeypox because it’s such a new disease in the United States, or they may not consider referring patients who aren’t in what they think of as at-risk populations. Although most cases have been in men who have sex with men, not all of them are. For example, health officials in Indiana have reported that about 20 percent of the state’s cases have been in women, and two infections have been identified in children.
Financial constraints, stigma, and lack of insurance or transportation to testing sites may also be barriers that prevent some people with symptoms from seeking testing.
The U.S. Food and Drug Administration says monkeypox should only be diagnosed with swab lesions, but a study published in June by researchers in Spain points to other possible ways to develop new tests to detect the virus They detected monkeypox viral DNA in both saliva and semen samples from 12 patients with confirmed infection.
The idea is already being pursued by Flow Health, a California company that has been offering tests for Covid-19. The company is working on a smallpox test that requires a person to spit into a plastic tube. Lab workers then perform a PCR test, extracting and amplifying viral DNA from the sample.
CEO Alex Meshkin says a saliva-based test could have benefits; for example, it could enable the screening of pre-symptomatic cases, which has been central to Covid-19 testing. It can also be done at a pharmacy, mass testing site or even at home, avoiding the potential embarrassment of seeing a doctor. “Relying on a lesion swab that’s painful and invasive and can only be done in a clinic will have inherently low demand because of the hurdles of traditional health care,” says Meshkin.
But in a safety communication released on July 15, the FDA warned that testing samples not taken from a lesion could lead to false positives. The agency noted that it is not aware of clinical data supporting the use of other types of samples, such as blood or saliva.
Rivers says it should be a research priority to develop other modalities, so that testing can reach as many people as possible: “It’s important to determine whether oral fluid testing, for example, is as accurate as the injuries”.