Monkeypox: Stop Testing Lesions Alone and Open Many More Testing Sites

Lao-Tzu Allan-Blitz, MD; Jeffrey D. Klausner, MD, MPH


August 02, 2022

In late 2019, as the COVID-19 pandemic was sweeping across the globe, the World Health Organization shipped tests to 57 countries. The United States was not one of those countries. Because of the declared public health emergency, the United States only allowed tests authorized by the Food and Drug Administration. That policy resulted in delays in testing for COVID-19 and subsequent rapid increases in viral transmission. We now face a similar junction, where we must expand our testing capacity for monkeypox in order to curtail the rapid and sustained increase in cases in the United States.

The Food and Drug Administration maintains that monkeypox testing must be performed on swabs from a skin lesion. The Centers for Disease Control and Prevention have provided similar guidance. The problem with that narrow thinking is that skin lesions, although perhaps the most impressive finding, are not always the first manifestation of monkeypox. Many, if not most, patients who have contracted monkeypox report a "prodromal period," or a period of fevers, fatigue, and swollen lymph nodes. During that period, it is possible that infected persons might spread infection to others.

The premise of restricting testing to lesions rests on the notion that only lesions are infectious. However, in prior outbreaks of monkeypox, human-to-human transmission via saliva was thought to occur in a subset of patients. Furthermore, emerging data show the ability to detect viral DNA in the saliva of infected individuals even before the rash has manifested. Identification of asymptomatic cases as well as the presence of viral DNA at various sites in the body has led many experts to suspect that patients with monkeypox have the potential to transmit the infection before the rash develops. Therefore, waiting for the rash to develop may serve to place close contacts of infected individuals at risk for infection and probably exacerbates the spread of the disease within the community.

The central component of our current public health strategy for containing the monkeypox outbreak is very similar to our response to the COVID-19 pandemic: case-finding, isolation, and contact-tracing, with the addition of postexposure immunization via a severely limited supply of vaccines. However, in order for that strategy to be effective, we have to identify cases before an infected individual spreads the infection within the community. Awaiting the appearance of the rash may directly subvert any utility of our current disease control strategy.

Increasingly, published reports from across the world are highlighting the utility of testing mucosal swabs from the rectum or oropharynx. In Belgium, asymptomatic cases of monkeypox were identified through rectal swabs. In a study of 12 cases of monkeypox in Spain, all 12 patients had positive saliva tests. Similar results have been reported in the United Kingdom. Throat swabs were also frequently positive (20 of 29) among tested cases in a large study across 16 countries. Notably, there are cases in which the throat swab will be falsely negative. However, studies have also documented false-negative swabs of a skin lesion. The point is not that all cases of monkeypox will be captured by oral fluid or throat swabs, but that many more will likely be detected — and detected sooner — than if we depend on lesion swabs exclusively.

It turns out that we can borrow more than the benefits of our experience with COVID-19 to combat monkeypox. Publicly accessible COVID-19 testing sites, of which there are many, can serve a dual purpose with the addition of monkeypox testing. Given the high rates of co-infection with sexually transmitted infections noted during the current outbreak, sexual health clinics, which routinely test rectal and throat swabs for sexually transmitted infections, can also incorporate routine screening for monkeypox on the same swabs.

The communities that are suffering most from the current outbreak are often already marginalized. Waiting for lesions to develop to test for monkeypox only ensures the continued transmission and continued suffering among those communities. We cannot afford to make the same types of mistakes we made early on in the COVID-19 pandemic: Testing must be rapidly expanded to include more than lesion swabs to facilitate early detection of cases, isolation, vaccination and treatment to curb the current outbreak. The opportunity to stop the spread of monkeypox is now.

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