Here’s why you won’t be testing for monkeypox at home anytime soon

Infectious disease diagnostics expert Dr Matt Binnicker explains how testing for monkeypox is done and how it differs from Covid-19.

Monkeypox virus, once thought to be a rare viral infection mostly confined to the African continent, has now been confirmed in more than 28,000 cases worldwide, including more than 7,500 in the United States. Last week, the Biden administration declared monkeypox a public health emergency, including plans to expand the availability of vaccines and testing.

Currently, the only way to confirm a positive monkeypox case is to send a sample to a lab, which is why the Centers for Disease Control and Prevention (CDC) recently partnered with 5 commercial labs to expand testing capacity.

Monkeypox is mainly transmitted by direct contact with a lesion (or rash) that contains the virus. Many cases in the current outbreak have been associated with sexual transmission of the virus. The disease can also be transmitted by contact with a contaminated object, such as a bedspread, towel, or clothing, that someone with monkeypox has recently used.

Once exposed, an individual may develop a flu-like illness (fever, headache, and body aches) within a week or two of being infected. Soon after, usually a few days after the first symptoms, a rash will develop, which can be isolated or found on several parts of the body. The rash can persist for several weeks and a person is considered contagious until the rash is completely healed.

While many Americans now rely on home testing to diagnose Covid-19, we are unlikely to see home testing for monkeypox anytime soon. Here are some of the main differences when it comes to testing for monkeypox versus Covid-19.

How is monkeypox testing done?

Throughout the pandemic, the world has become familiar with various types of laboratory tests to diagnose Covid-19, including PCR, antigen and serology (also called antibodies) tests. One of these tests, PCR, is also the recommended method for diagnosing monkeypox.

Despite the similarities between the technology used to detect monkeypox and Covid-19, there are important differences. Firstly, the virus that causes Covid-19 is most commonly found in the respiratory tract i.e. nose, throat and lungs, while the monkeypox virus is most common in a rash. Therefore, if someone is suspected of having monkeypox, their doctor will use a swab to collect cells from the rash and then send the swab to a testing lab.

The lab will first separate any monkeypox virus DNA from the cells and proteins that are also present. The PCR test next »looking for“a small piece of viral DNA (unique to the monkeypox virus), and if present, that specific region of the virus genome is copied – or amplified – by the thousands, and potentially millions, times. Each time a new copy is made, a fluorescent light signal is produced and eventually enough light is generated for the PCR test to be positive.

A second key difference is that PCR and antigen testing have been widely used throughout the Covid-19 pandemic to identify people who are infected but asymptomatic, i.e. without symptoms of the disease. In contrast, monkeypox is not known to be efficiently transmitted by those without symptoms, so asymptomatic testing is unlikely to be common as the monkeypox epidemic unfolds. unfolds.

Will we soon have access to home testing for monkeypox?

Over the past year, there has been a rapid expansion in the availability of home tests to diagnose Covid-19. Americans even have the option of ordering free antigen tests that will be shipped directly to their homes. Will home testing for monkeypox soon become a reality? The short answer is that it’s unlikely. Most home tests are antigen-based, meaning they test for a viral protein that may be present in the sample. Because antigen tests look for protein rather than viral DNA, they are less sensitive than PCR tests. This means that an antigen test can be negative even if the person being tested has the disease.

There are currently other more common causes of rashes that can result from sexual transmission, including herpes and syphilis. Since many cases of monkeypox result from sexual transmission, it is highly likely that laboratories will use PCR tests to assess the multiple potential causes of the patient’s illness. Given that the ongoing monkeypox epidemic has resulted in tens of thousands of cases in more than 80 countries, it is unlikely to be contained.

There is a growing possibility that monkeypox may become an endemic sexually transmitted infection that should be considered in patients with rash-like illness following intimate exposure with a new partner. As the number of cases increases, new tests will likely be developed, including those that allow an individual to collect their own sample at home (but send that sample to a lab for analysis), tests multiplexes that test a sample for multiple diseases (such as monkeypox, herpes, syphilis) in the same test, and potentially in the future, those that do not require submitting samples to a clinical laboratory. Hopefully lessons learned from Covid-19 will translate into innovative testing options to curb the spread of monkeypox.

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