Players from the Pittsburgh Pirates and Miami Marlins have raised significant concerns about their upcoming series in Puerto Rico, expressing fear of exposure to the Zika virus, multiple league sources told Yahoo Sports.

Officials from Major League Baseball and the MLB Players Association have not yet given serious consideration to canceling the two-game series, scheduled to be played at Hiram Bithorn Stadium in San Juan on May 30-31, according to sources. But the sides plan on continuing to weigh the potential danger to teams and their families before making a decision, sources said.

"The health and safety of our players and staff is our No. 1 priority," said Brian Warecki, the Pirates' vice president of communications. "We are working closely with all parties, including MLB, MLBPA and the CDC, to ensure we are fully educated on the issue. We are very confident that we are taking the overly cautious steps to ensure we have a very successful two-game series in San Juan."

The Marlins declined comment.

Samples of mosquitoes responsible for transmitting dengue and Zika sit in a petri dish. (AP) More

Around 400 cases of the virus, spread by mosquito bites and through sexual contact, have been confirmed in Puerto Rico. The Center For Disease Control has estimated upward of 700,000 people – about 20 percent of Puerto Rico's population – could be infected by the end of the year.

The virus has been linked to birth defects in babies, a worry for multiple players who have considered having children in the near future, sources told Yahoo Sports. Other players have expressed no apprehension about the series in Puerto Rico, and the lack of unanimity inside the clubhouses has clouded the decision about how to proceed, sources said. The league plans to bring in experts from the CDC to address the subject of Zika and give players a sense about its danger, sources said.

"We believe the games will be played as scheduled, and we are having ongoing conversations with the CDC to alleviate the players' concerns," said Patrick Courtney, MLB's chief communications officer.

The Marlins and Pirates are not the only teams that have taken Zika precautions. Multiple organizations with personnel that regularly travel to Caribbean countries for scouting trips have advised employees planning on having children in the near future to skip scheduled visits, sources told Yahoo Sports.

The concern goes beyond baseball. Olympic athletes have grappled with the specter of Zika in Brazil, the epicenter of the outbreak and home to the 2016 Summer Games. The CDC has recommended pregnant women not travel to Rio for the event this August.

Nearly $2 billion in emergency Zika prevention funding requested by the Obama administration still hasn't been approved, even after the World Health Organization deemed the virus a global health emergency. While cases of Zika in the United States have been linked to those contracting the virus in other countries and returning to the United States with it, Dr. Anthony Fauci, the director of the U.S. National Institute of Allergy and Infectious Diseases, told Fox News on Sunday that he expects the mosquitoes carrying the virus to reach U.S. soil this summer.

"It is likely," Fauci said, "we will have what is called a local outbreak."

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