COVID-19 is making a concerning comeback, according to World Health Organization (WHO) officials, who warned this week of new waves of infections across the world while urging governments everywhere to launch new vaccination campaigns to persuade more people to get the shot.

“The perception that COVID is gone is real, but the virus isn’t gone,” Dr. Maria Van Kerkhove, the COVID-19 technical lead at the WHO, told reporters at a press conference in Geneva, Switzerland, on Aug. 6.

Kerkhove said the health agency’s global surveillance system has detected that infections with SARS-CoV-2 are on the rise and that there’s a risk that potentially more dangerous new variants will emerge.

“Data from our sentinel-based surveillance system across 84 countries reports that the percent of positive tests for SARS-CoV-2 has been rising over several weeks,” she said. “Overall, test positivity is above 10 percent, but this fluctuates per region.”

In Europe, where the Paris Olympics are being held, the COVID-19 percent positive is above 20 percent, according to Kerkhove.

At least 40 Olympic athletes have tested positive for the virus in Paris, per the U.N.-based health agency.

The recent spike that triggered Kerkhove’s warning has yet to be reflected in data that countries report to the WHO, which are current as of July 21. The data show that cases have been within a weekly range of 30,000 to 40,000 since mid-April following a seasonal spike over the winter months that got as high as 382,000 weekly cases.

Deaths from COVID-19 have been at their lowest level since the pandemic over the past several months, within a range of 475 deaths to 660 globally per week since April, with no indication of an uptick.

Kerkhove also warned that as the SARS-CoV-2 virus spreads and evolves, there’s a risk that a new mutant version will emerge that defies detection and resists medical interventions, including vaccines.

“If we were to have a variant that would be more severe, then the susceptibility of the at-risk populations to develop severe disease is huge,” she said.

Kerkhove said the WHO is urging governments around the world to start campaigns to persuade more of their citizens to get vaccinated. In particular, she said at-risk groups should get the vaccine at least once every 12 months.

There has been some controversy about vaccination campaigns in light of concerns about the efficacy and safety of the COVID-19 vaccines, particularly as evidence has emerged about side effects that were not detected in trials.

However, health officials continue to maintain that the benefits of COVID-19 vaccines outweigh their risks.

Concerns about vaccine efficacy center on the fact that the virus is continuously mutating and that vaccine development targets variants that may already be on the wane when the new vaccines are rolled out. In June, advisers to the Food and Drug Administration said it’s time to update the recipe for the vaccine that will be widely used in the fall, targeting a version of the virus called JN.1.

The advisers were of the view that, even though there is a newer variant called KP.2 already circulating, JN.1 is a parent variant, and so focusing the vaccines to target it, as opposed to the newer version, is better because it’s more likely to offer some cross-protection against various subvariants.

At the press conference in Geneva, Kerkhove highlighted that vaccine availability has declined over the past year or so as the number of vaccine manufacturers has decreased.

“I am concerned,” Kerkhove said, expressing hope that nasal COVID-19 vaccines, which are still being developed, would be finalized and rolled out quickly.

Nasal vaccines have been viewed as promising because they target the virus where it first enters the body, in the nose and throat. By doing so, they could offer stronger and more localized immunity at the entry point, which could help in curbing transmission and lowering the risk of new variants emerging, according to the National Institutes of Health, which is sponsoring the first in-human trial of the investigational nasal vaccine.

Kerkhove said the decline in vaccine coverage over the past two years has been “alarming.”

“This urgently needs to be turned around,” she said.

The WHO official’s remarks about a global uptick in COVID-19 cases come as data from the Centers for Disease Control and Prevention (CDC) show that more than two-thirds of all U.S. states are experiencing “high” or “very high” levels of COVID-19 infection.

Twenty-three states are seeing “very high” levels, according to a map of wastewater data updated on Aug. 1 by the CDC. Twenty-one states are experiencing high levels, the data show.

Just two states—New York and Virginia—are reporting “low” levels of COVID-19, per the CDC map.

Despite the recent rise in cases in the United States, data published by the CDC show that the total U.S. deaths per week from COVID-19 are at their lowest levels since the start of the pandemic in early 2020.

For the week that ended on July 27, there were a total of 304 deaths from the virus, per the CDC data.