150 public health experts are calling on the World Health Organization (WHO) and International Olympic Commission (IOC) to postpone or relocate the 2016 Summer Olympics in Rio de Janeiro in response to the outbreak of Zika virus in that city that has infected thousands and caused thousands of cases of birth defects in infants.

The letter, published on social media Friday, was authored by four prominent public health academics and signed by dozens of others who note that Olympic Games have been postponed, even canceled entirely, over security concerns, and that the risk of triggering a global spread of the aedes aegypti mosquito, which carries Zika, is not worth the perceived benefits of holding the Games at their scheduled time.

“The 1916, 1940, and 1944 Olympic Games were not just postponed, but cancelled, and other sporting events were moved because of disease, as Major League Baseball did for Zika, and the Africa Cup of Nations did for Ebola,” the authors write. “An unnecessary risk is posed when 500,000 foreign tourists from all countries attend the Games, potentially acquire that strain, and return home to places where it can become endemic.”

The authors call it “unethical to run the risk” of spreading Zika through the thousands of tourists expected to visit Rio de Janeiro for the Olympics, particularly given that Rio is a hotspot for Zika, even in Brazil, the nation most affected by the current outbreak. “Brazil’s government reports Rio de Janeiro state has the second-highest number of probable Zika cases in the country (32,000) and the fourth-highest incidence rate (195 per 100,000), demonstrating active transmission,” the authors note.

The Washington Post notes that the signatories to the letter include representatives from over a dozen countries around the world. Those from nations not affected by Zika fear the introduction of the virus into these new climates. The authors add that the rates of dengue fever in Brazil, also transmitted through the aedes aegypti mosquito, have been growing, as well.

The letter not only requests that the Olympics be postponed but challenges the World Health Organization to prove that it has no vested interest in the Games going on as scheduled, regardless of whether they post an international health risk. The authors accused the WHO of having a “troubling” response to calls to reschedule the Games and request transparency in the group proving it does not have a “conflict of interest.” The letter is addressed to Dr. Margaret Chan, the head of the WHO.

Two of the authors of the letter, NYU’s Art Caplan and the University of Ottawa’s Amir Attaran, have been calling for the Olympics to be postponed for months, until the full extent of how much research would be required to fully understand the threat of Zika became clear. “Are you really going to try to run the Olympics this August in the middle of a public health emergency when the country can’t afford to finish the buildings, and has got to take on the mosquitos?” Caplan asked in February, suggesting that taking one’s family into Rio de Janeiro during the Zika epidemic would be like saying “Let’s visit Chernobyl to enjoy the Olympics!”

Speaking to Breitbart News Daily’s Stephen K. Bannon in February, Caplan suggested taking “six months, get nine months, postpone this… Develop a good diagnostic test. Get something that lets us test the blood supply. Make sure that we’ve killed all the mosquitoes. You know – let’s use some common sense here.”

Attaran recently published an article in the Harvard Public Health Review calling for the Olympics to occur later in the year or in another location. His has been the most scathing criticism of the WHO to date, calling the organization’s action in response to the Zika outbreak “deplorable, incompetent, and dangerous.”

“Mass migration into the heart of an outbreak is a public health no-brainer,” Attaran warned.

The Zika virus typically produces no symptoms in an estimated 80 percent of the people in infects. In the 20 percent that experience symptoms, these tend to be mild fevers, aches, and conjunctivitis. The real threat of Zika, experts content, is to the unborn child.

Children born to women who have been bitten by Zika carriers during their pregnancy are significantly more likely to develop neurological birth defects. In Brazil, the most common defect has been microcephaly, a condition in which an infant’s skull is smaller than its brain, crushing the brain and causing severe developmental problems. Many of the thousands of children with Zika-linked microcephaly in Brazil have died early, and scientists are unsure how much special care those who survive will need in their lifetimes.

A study released in May found that the strain of Zika in Latin America is new and significantly more dangerous than the known strains in Africa and the south Pacific.

The IOC has repeatedly asserted it will not postpone or move the Olympics, however. “The IOC absolutely is not complacent. We do take this very seriously…. Everything is being done to contain and reduce this problem in the lead-up to the games,” Dr. Richard Budgett, medical director of IOC, said in February. In April, the IOC issued a statement confirming the Games will go on: “The Brazilian people will deliver a memorable Olympic Games full of passion for sport for which they are world renowned… The Olympic Games will deliver an important legacy and provide an important opportunity to unite the people of Brazil no matter their background or political views.”