Portela: Naomi Campbell can no longer parade with them
On Friday afternoon, a costumed man in Rio de Janeiro, Brazil, took possession of a huge fake key from the city's mayor - initiating a week of the wildest merriment in the world.
Rio's carnival is a festival of music, dance and costume that will eventually burn itself out next Wednesday.
But carnival is not immune from the changes affecting Brazilian society, and a new problem is afflicting Rio as it prepares for its yearly party.
Dengue fever has swept through the city and has even struck the carnival's Rei Momo - the "fat king" to whom mayor Cesar Maia symbolically gave the keys to Rio on Friday.
Now carnival floats are being sprayed with insecticide to prevent transmission of the disease, carried by mosquitos.
Another complaint being made by the people of the favelas - the shanty towns where the carnival's samba schools are based - is that carnival is becoming too commercialised.
Seats in the Sambadromo, a custom-built stadium through which the samba school parade, are priced well beyond anything which ordinary Rio residents can afford.
And the carnival themes adopted by the samba schools are being increasingly influenced by financial donors.
This year, the Grande Rio samba group received nearly 2m reals (£574,000) to sing the praises of the northeastern state of Maranhao - where the governor is a leading candidate in Brazil's upcoming presidential election.
Influence
A rival school is getting a similar amount to laud the city of Campos, the electoral base of another presidential hopeful - while two other schools will tell the history of aviation, after donations from Brazilian airlines.
And the sambistas - the composers and musicians who used to be at the centre of carnival - are losing influence on the event.
"The groups used to be run by sambistas - now they're run by businessmen," said Noca de Portela, a veteran samba singer and composer, who has written five winning sambas for the Portela school.
"It's become a party for tourists.
"Once, most of the people parading were from the neighborhoods - now they can't even afford to buy a costume."
But, if past years are anything to go by, these grumbles will be forgotten by the time the samba schools start parading on Sunday and Monday nights.
Fourteen top samba schools - each with some 4,000 costumed dancers and drummers - will parade the 700m-long Sambadromo, cheered on by thousands of singing, cheering fans.
They will be competing for the prize of top samba school, won last year by Beija-Flor.
In the audience this year will be Barbara Bush, wife of George Bush Sr and mother of George W Bush.
But supermodel Naomi Campbell has had to return to the UK where her privacy lawsuit is being heard by the High Court - despite having spent a week learning how to samba at the Portela samba school.