A crippling disease in the Indian Ocean island of Reunion has affected 157,000 people, one in five of the population, in the past year, health officials say.
Insecticide spray is being used to try and eradicate the disease
Chikungunya, Swahili for "that which bends up", causes high fever and severe pain but was not thought to be fatal.
However, the health minister of France, which rules the island, said this week 77 deaths may have been caused "directly or indirectly".
Prime Minister Dominique de Villepin is to visit the island on Sunday.
There have also been cases of chikungunya in Mauritius, the Seychelles and Madagascar.
French Health Minister Xavier Bertrand increased fears over the outbreak when he said the mosquito-borne disease could have caused fatalities.
He told Le Figaro newspaper on Thursday this was a "radically new situation, that was not anticipated or foreseen by any scientific theory, according to which chikungunya does not kill".
The prime minister's office said Mr de Villepin would "announce the reinforcement of personal aid and an increase in repellent equipment, with pregnant women, the elderly and children the principal beneficiaries".
Mr de Villepin rejected claims France had failed to take account of the growing health crisis in Reunion.
"We are face-to-face with a devastating epidemic which suddenly accelerated at the start of the year. Developments went beyond all the predictions made by experts," he said.
The outbreak has hit tourism. Industry representatives say bookings are down 60% since December.