With the United States on the lookout for more monkeypox cases, federal health officials this week said they’re considering expanding testing networks, even as they’ve stressed the current two-step process is not delaying treatment or containment of the outbreak.

For possible monkeypox cases, swabs from the patient are sent to both a local or state lab for initial testing, and to the Centers for Disease Control and Prevention for confirmatory testing. The initial tests identify whether the sample is an orthopox — the genus that monkeypox belongs to — while the CDC verifies that it is in fact monkeypox. The process explains why local communities are announcing suspected cases, followed by confirmation a few days later.

The CDC has faced questions about whether the protocol might prolong infection detection, at a time early in the outbreak when active case investigations and severing transmission chains can prevent the virus from becoming established in communities. The scrutiny is heightened by memories of the Covid-19 pandemic’s early days, when faulty tests and slow regulatory action left the country with a dearth of testing capacity — and a hindered ability to track the virus as it exploded.

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But with monkeypox, regional and federal health authorities have underscored they’re treating any suspected cases as presumptive cases, using that information to steer clinical care of patients and to launch contact tracing. They’re not waiting on CDC confirmation to do that.

“I want to emphasize that the orthopox test that they have is sufficient for managing patient care and contact tracing and all of those things,” Jennifer McQuiston, deputy director of the CDC’s division of high consequence pathogens and pathology, told reporters this week.

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Still, McQuiston said that officials are weighing how to expand testing capabilities to other labs, if that becomes necessary.

“It’s not an easy matter to shift the tests out to the states,” she said. “And I think we’re actively exploring what it would take. I’ll just tell you that we’re committed to, if it’s possible, doing it as quickly as we can.”

Gigi Gronvall, a senior scholar at Johns Hopkins’ Center for Health Security, said the current two-step system can be effective, “as long as they’re still doing the contact tracing as necessary based on the presumption” from the initial testing. If the outbreak continues to grow, perhaps the CDC’s capacity might not be able to keep up, she said, but other facilities should be able to handle monkeypox testing.

The testing protocols for monkeypox stem from the country’s smallpox preparedness planning. When someone seeks care for a suspicious rash, facilities in what’s called the Laboratory Response Network — a collection of state, local, veterinary, and military labs tapped to test for biological or chemical threats — perform the initial test to see if the cause is an orthopox virus. Samples are also sent to CDC to confirm which type. The system for poxviruses was designed specifically so the CDC would handle any cases of smallpox, McQuiston said. (Smallpox, which once was often lethal, is the only human disease that’s been eradicated, but a small number of labs have stores of the virus that causes it for research purposes.)

In the United States, 74 of the labs in the response network in 46 states can run orthopox tests, with a capacity to do nearly 7,000 tests a week, CDC Director Rochelle Walensky said at a briefing this week.

“In this circumstance, an orthopox diagnosis at the LRN is monkeypox until proven otherwise,” said John Brooks, a CDC medical epidemiologist.

Chris Mangal, the director of public health preparedness and response at the Association of Public Health Laboratories, explained that labs in the LRN aren’t equipped to test for monkeypox because it’s been so rarely seen in the United States. Otherwise, they would have to maintain assays and ensure that the necessary materials are available and stored properly.

Mangal said she didn’t think other labs would need to start testing specifically for monkeypox unless the outbreak grew much larger. The CDC could distribute assays to other labs, but there are specific rules and regulatory requirements for how that process works and when it can be done. Labs can also develop their own tests, which would need to meet certain regulatory standards.

From a technical standpoint, “it’s not a difficult process, but there are a couple things they have to do,” she said.

At the CDC, PCR tests not only determine if samples are indeed monkeypox, but if so, which clade they belong to. (The cases in the current outbreak have been from the West African clade, which is typically less severe than the Congo Basin clade, with a suspected case fatality rate of 1% or lower.) The CDC has also been sequencing cases, which can help scientists track how the virus has been spreading globally.

Monkeypox is a very different pathogen than the coronavirus that causes Covid — it’s a much less efficient spreader, for example — and this isn’t an instance where scientists are having to design a test for a never-before-seen virus. There have been monkeypox cases in the United States in the past.

Many of the cases identified in the global outbreak have occurred in men who have sex with men, and many were identified at sexual health clinics. Health officials are scrambling to raise awareness ahead of Pride Month, even as they’re stressing that other people are susceptible to contracting the virus as well.

So far, more than 300 confirmed and suspected monkeypox cases have been detected in about 20 countries outside those in West and Central Africa where the virus is endemic. Walensky said Thursday the United States has nine cases, some of which have travel histories to areas where the virus is spreading and some of which do not, an indication of domestic transmission.

Meanwhile, Roche announced this week it had developed monkeypox diagnostic tests that it was making available around the world.

Helen Branswell contributed reporting.

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