It may meet sooner if warranted, he added.

“I continue to be concerned about the scale and spread of the virus,” Adhanom Ghebreyesus said at a press briefing. “Testing remains a challenge, and it’s highly probable a significant number of cases are not being picked up.”

Global cases rose from 5,800 on Friday to nearly 7,000 Tuesday, according to U.S. Centers for Disease Control and Prevention data. Friday’s tally was double that of six days prior, June 25, when the decision not to declare an international health emergency was announced by the WHO.

Last week, WHO officials had said the committee would reconvene again soon due to the “evolving situation,” citing the virus’s move into the pediatric population and its “rapid evolution” and spread.

While it appears as if the virus could be mutating rapidly due to recent abnormalities in its spread and physical presentation, such observations may be attributable to a failure in surveillance, Dr. Michael Ryan, executive director of the WHO’s health emergencies program, said in a response to a question asked by Fortune.

“When we look once and look again, did the virus change abruptly, or was our surveillance very poor?” he said, calling for an expansion of genomic sequencing, including real-time sequencing, in Africa. “I think we can say with monkeypox that the surveillance is very poor.”

“What we’re actually seeing at the moment is a little bit like the drunk man looking for his keys under the lamppost. We’re looking where the light is, but we’re not looking in the dark.”

When asked if the further mutations in the virus had been detected beyond the “at least two genetically distinct variants” announced by U.S. officials in early June, WHO officials offered no updates, citing the length of time it takes to sequence a genome.

All strains reported outside of Africa since May, the beginning of the global outbreak, belong to the West African clade, less severe than the other known clade, the Congo Basin, health officials have said. The two new strains previously reported by U.S. health officials were also said to belong to the West African clade.

Threat growing ‘with every hour, day, and week’

In a Friday statement, Dr. Hans Henri P. Kluge, WHO regional director for Europe, said there is “no room for complacency” in the battle against the virus, calling it a “fast-moving outbreak that with every hour, day, and week is extending its reach into previously unaffected areas.”

Nearly 10% of patients have been hospitalized, but there have been no deaths in the region, he said.

“Urgent and coordinated action is imperative if we are to turn a corner in the race to reverse the ongoing spread of this disease,” he added.

Monkeypox is usually found in rural African areas where people have close contact with infected rats and squirrels. Recent cases, however, have occurred in countries where the virus has not previously been seen, and in individuals without a travel history, indicating that it likely has been circulating unnoticed for some time.

When the virus is transmitted human to human, it’s typically through close contact, which may include sex and could include contact with personal items like sheets and clothing. While it’s not considered a sexually transmitted infection, public health officials say many recent cases have been found among men who have sex with men, and note that it’s difficult to tease out sexual transmission from close-contact transmission. Airborne transmission is known to be possible but has yet to be confirmed.

With smallpox declared eradicated by the WHO in 1980 and the vaccine for it, which works on monkeypox, no longer widely administered, the population has a low level of immunity against poxviruses, WHO officials have said. That means transmission into the wider population could occur.

Symptoms are similar to but milder than those of smallpox, according to the CDC. Initial symptoms usually include fever, headache, muscle aches, and exhaustion. Within one to three days, patients develop a rash, usually starting on the face and then spreading to other parts of the body. Lesions progress through various stages before scabbing. The illness usually lasts two to four weeks. The typical incubation period is seven to 14 days but can range from five to 21 days.

But symptoms in new cases appear to differ from those of classic cases—at least in some instances—with recent reports of lesions more subtle than usual and some cases involving just one lesion, health officials have said.

WHO emergency committees currently exist only for COVID-19 and polio. Seven additional past emergency committees have previously been convened for diseases including Ebola, H1N1, and MERS.