Millions of people joined in to celebrate the first day of the annual Carnival of Brazil, dismissing concerns over an outbreak of the mosquito-borne Zika virus which has been linked to birth abnormalities.

Huge crowds of revelers filled the city center in Brazil’s Rio de Janeiro while in Recife, the city most affected by the disease, more than a million people were partying, according to media reports.

The health ministry and local authorities have been handing out leaflets alerting residents and tourists to the risks of Zika, and telling people to use insect repellent and appropriate clothing. Brazilian authorities said Friday the virus had been detected in patients' saliva and urine, adding to concerns over the spread of the virus at the crowded festival.

The virus has spread rapidly to about 30 countries in the Americas, prompting the World Health Organization to declare an international public health emergency due to its link to microcephaly, a condition in which infants are born with abnormally small heads and can suffer developmental problems. Most people that contract the virus show no symptoms or experience only mild symptoms like a fever, headaches and rashes.

There is currently no vaccine or medicine for Zika.

However, hotel occupancy rate in Rio de Janeiro was expected to hit 85 percent, significantly higher compared to last year, CNN reported, while hotels in Recife were at 93 percent occupancy.

Brazil — faced with a recession last year along with a huge corruption scandal in the state-owned oil company — had to make small cuts to the five-day festival this year, with some smaller cities such as Cruz Alta and Santo Angelo in southern Brazil cancelling celebrations completely. In Sao Paulo, Brazil's largest city, party organizers reportedly said they had to find ways to cut down expenses.