RIO DE JANEIRO (AP) — Some Paralympians face more risks than Olympic athletes from the Zika virus and filthy water in Rio de Janeiro, the medical and scientific director of the International Paralympic Committee told The Associated Press in an interview on Wednesday.

Peter Van de Vliet said he had not heard of any Paralympic athletes pulling out of Rio, but acknowledged the threat.

"Having said that, we do have a certain athlete population that might be a bit more vulnerable to infection," Van de Vliet said. "There is definitely, by the nature of certain impairments, a group of athletes that might need a little higher threshold to fight an infection."

The Paralympics open Sept. 7 with 4,350 athletes, preceded by the Olympics, which run Aug. 5-21 with 10,500.

Van de Vliet listed athletes with spinal-cord injuries, and some with cerebral palsy as a group at higher risk.

To illustrate physical problems, he used the example of athletes who have lost both lower limbs and have trouble regulating body temperature. Or athletes with "intellectual impairments" that are vulnerable because of poor hygiene habits, or the visually impaired simply not being able to see open wounds.

"Also, you should never forget that these are athletes," Van de Vliet said. "That means that across the board their resistance to any kind of negative impact is — by default — a little higher than the normal (impaired) population."

Van de Vliet, who will be in Boston this week for the annual meeting of The American College of Sports Medicine , said part of the conference included a special section on preparing athletes for Rio de Janeiro.

Van de Vliet said Paralympic athletes would be getting the same advice given to Olympic athletes about the bacteria and viruses in Rio's waters — and the Zika virus, which has been shown to cause birth defects.

The Paralympic Games seem to have avoided the problems with doping that are dogging the Olympics. The International Olympic Committee announced recently that up to 55 athletes have tested positive for doping in a reanalysis of samples from the past two Summer Olympics.

Van de Vliet said the popularity of Paralympic sports had mushroomed in the last 10 years. Though good news, it also means that the threat of cheating had increased.

"I strongly believe we are not exposed to the same risk or abuse as Olympic athletes," Van de Vliet said. "Having said that, we clearly should not be naive."

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Stephen Wade on Twitter: http://twitter.com/StephenWadeAP .His work can be found at http://bigstory.ap.org/content/stephen-wade