TORONTO -- The World Health Organization (WHO) is warning that countries lifting public health restrictions too early could see an “immediate second peak” in COVID-19 cases, even if new diagnoses are currently declining in their region.

In a virtual press briefing Monday, Dr. Michael Ryan of the WHO said that although cases are on their way down in many countries, the world is still “right in the middle of the first wave, globally.”

The concept of a second wave of cases after the virus has been beaten down once is a major source of concern. But we haven’t suppressed the virus to a degree where a second wave is the next worry, Ryan said.

“When we speak abut a second wave classically, what we often mean is that there’ll be a first wave, the disease […] goes to a very low level, and then it [goes back up] a number of months later,” he said in the press briefing. “And that may be a reality for many countries in a number of months’ time. 

“But we need to be also cognizant of the fact that the disease can jump up at any time,” he added. “We cannot make assumptions that just because the disease is on the way down now, that it’s going to keep going down and we’re going to get a number of months to get ready for a second wave.

“We may get a second peak in this wave.”

He said that a second peak in cases within the first wave of a pandemic is something that has happened before in the past, such as with the influenza pandemic of 1918, sometimes called the Spanish Flu.

In order to avoid having cases skyrocket for a second time within the first wave, Ryan said that countries in Europe, North America and Southeast Asia should “continue to put in place the public health and social measures, […] the testing measures and a comprehensive strategy, to ensure that we continue on a downward trajectory.”

Ryan added that the situation is very different depending on where in the world one is, pointing out that countries such as Spain have managed to “contain and suppress the disease transmission,” while in other regions such as South America, Africa, South Asia, and “many other countries, we’re still very much in a phase where the disease is actually on the way up.”

Many countries have already started to ease their lockdown measures and reopen some workplaces and public areas in a bid to lessen the economic impact of the pandemic. Japan lifted the state of emergency over Tokyo and four other remaining regions on Monday, ending their nation-wide restrictions.

In Canada, some provinces are beginning to reopen in stages after days or weeks of no new cases, or relatively low case numbers, but Ontario and Quebec have come under fire for beginning to reopen retail and workplaces despite daily case numbers still being in the hundreds.

Quebec leads the country in COVID-19 deaths. In Ontario, the case numbers have climbed over the past few days and the number of tests conducted has been far below the province's capacity.

Tedros Adhanom Ghebreyesus, director-general of WHO, said that the lifting of public health measures such as lockdown orders should not come with complacency.

As restrictions on the population are lifted, the base of the health-care response in terms of things such as contact tracing and testing should “be strengthened,” he said.

“We remind all countries who are lifting the serious measures they had to make sure that the public health measure, the comprehensive approach is in place, and the right instruments are actually continuing to be implemented,” he said.”

Dr. Maria Van Kerkhove of WHO also stressed the importance of remaining vigilant.

“Let us be perfectly clear: all countries need to […] remain on high alert here,” she said. “Even countries that have seen a decline in cases must remain ready.

“The virus will take that opportunity to amplify, if it can.”