U.S. health officials have concluded that infections by the mosquito-borne Zika virus in pregnant women can cause microcephaly, a birth defect marked by small head size that can lead to severe developmental problems in babies.
However, Picciani, who was appointed by interim President Michel Temer, said the situation had significantly improved.
"We hosted 43 test events in Rio with 7,000 athletes and we have not had any case of Zika or dengue," he told BBC Rio de Janeiro.
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"We had 4,300 cases in April, which fell to 700 in May and there will be another significant reduction in June or July, and in August it will be very close to zero.
"All the mechanism of prevention and protection are guaranteed. I would say to any athlete, to any visitor planning on coming to Rio, you do not have to worry, Rio and Brazil have prepared for this moment."
Golfer Jason Day became the latest athlete to cast doubt over his participation in Rio, after U.S. cyclist Tejay Van Garderen withdrew from the Games over concerns that the outbreak could present risks for his pregnant wife.
(Reporting by Nivedita Shankar in Bengaluru; Editing by John O'Brien)
