Blasting the World Health Organization’s (WHO) silence on the Zika virus in Latin America as “deplorable, incompetent and dangerous,” professor Amir Attaran writes in the Harvard Public Health Review that there is no way to continue with the Summer Olympic Games in Rio de Janeiro, Brazil, on schedule without exposing millions to the threat of contracting Zika virus.

Attaran, a professor at the University of Ottawa, writes in the May issue of the publication that the threat of contracting Zika in Rio de Janeiro appears to have increased, not decreased, in the past few months, and that the more doctors understand the threats associated with the virus, the more dangerous it appears to be.

“Simply put, Zika infection is more dangerous, and Brazil’s outbreak more extensive, than scientists reckoned a short time ago.  Which leads to a bitter truth: the 2016 Olympic and Paralympic Games must be postponed, moved, or both, as a precautionary concession,” he writes. He supports his conclusion by noting that Rio de Janeiro is “inside the heart” of the outbreak, with the state of Rio de Janeiro having the highest number of cases nationwide. (Brazil is the epicenter of Latin America’s Zika outbreak, with Colombia and Venezuela suffering high numbers of cases, as well.)

To eradicate the threat, Attaran notes that scientists must first slow down the spread of the virus to have the time to develop the complex technologies necessary to eliminate it from the population. This, he says, is impossible with an injection of half-a-million foreigners into the population, who will leave the country in two weeks to spread the virus throughout the world. Simply put, he concludes, “Mass migration into the heart of an outbreak is a public health no-brainer.”

Attaran calls proceeding with the games given the threat an unethical stance and saves his harshest criticism for the WHO, which he notes “has never issued an official statement on Zika and the Olympics,” and has joined the International Olympic Commission (IOC) in optimistic “denial” of the problem.

Attaran joins a number of public health experts in calling for the Olympics to be relocated or postponed, noting that precedent exists for such a move. In February, Dr. Art Caplan of the NYU Langone Medical Center told Breitbart News he wholly supported the postponement of Olympic Games until athletes could feel safe traveling to Rio de Janeiro, arguing that traveling there this year would be like holding the Olympics in Chernobyl.

The WHO has not budged on its position regarding Zika. Earlier this week, WHO spokesman Christian Lindmeier told reporters that the organization is “confident” that the Olympics will be a success, as Brazilian health officials have appropriately managed the reduction of the population of aedes aegypti, the mosquito responsible for transmitting Zika.

While Zika is largely asymptomatic in adults, and causes only mild symptoms in those who feel anything at all, scientists have found that the strain of Zika currently spreading through Latin America can cause severe brain damage in unborn children when entering the bloodstream of a pregnant woman. It has also been linked on rare occasions to Gullain-Barré Syndrome (GBS) in adults, a neurological disorder causing extreme muscle pain, paralysis, and death.

A study published in late April found that, due to travel and migration patterns, as well as the prevalence of aedes aegypti, more than two billion people are at risk of being exposed to Zika worldwide.

Athletes have expressed serious concerns with participating in the Olympics. American soccer goalkeeper Hope Solo, who threatened not to participate in the games because of Zika, has announced that she will go, but she will likely not spend much time sightseeing in Rio. “I’m not sure I’m even going to be leaving the hotel room, outside of practice,” she told CBS Sports this week.

Rivaldo, a Brazilian soccer star who was part of the last national team to win the World Cup, warned tourists against coming to the Olympics this year, arguing that Rio de Janeiro is getting “more ugly,” and the combined threats of crime and disease are not worth being part of an Olympics ceremony.