Golf's world number one Jason Day has announced he will not participate in this summer's Olympic Games in Rio de Janeiro because of concerns over the Zika virus. The 28-year-old Australian has joined Rory McIlroy in withdrawing from the event due to health concerns.

The 2015 PGA Championship winner admitted the risk of contracting the mosquito-borne virus is small, but Day said it is one he is unwilling to take as he plans to have more children. The virus has been linked to brain defects in newborn babies.

"The reason for my decision is my concerns about the possible transmission of the Zika virus and the potential risks that it may present to my wife's future pregnancies and to future members of our family," he explained in a statement posted on Twitter.

"I have always placed my family in front of everything else in my life. Medical experts have confirmed that while perhaps slight, a decision to compete in Rio absolutely comes with health risk to me and to my family."

The announcement comes shortly after McIlroy announced he would not be competing in Brazil either. "After much thought and deliberation, I have decided to withdraw my name from consideration for this summer's Olympic Games in Rio de Janiero," McIlroy – who planned to compete for Ireland in Brazil – said in a statement.

"I trust the Irish people will understand my decision. The unwavering support I receive every time I compete in a golf tournament at home or abroad means the world to me. I will continue to endeavour to make my fans and fans of golf proud with my play on the course and my actions off it."

Previously, Fiji's Vijay Singh and Australian Marc Leishman withdrew because of concerns over the virus, while Adam Scott, Louis Oosthuizen and Charl Schwartzel have already announced they will not take part due to scheduling reasons. Day's decision is another major blow for the sport, which is returning to the Olympics after a 112-year absence.