It is advisable to pay extreme attention not to lose your passport: there are very few consulates in French Guiana as such services are provided by consulates in Paris, so you will be required to go to Paris in case you need your passport to be reissued if you are not an EU citizen.
Vaccination against yellow fever is necessary.
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French is the official language of France, although Creole is widely spoken. The majority of the population speaks French while few understand English. However, some officials, police, and gendarmes may speak English. Because of the presence of many Brazilians and Dominicans, lots of people understand basic Portuguese and basic Spanish. On the Maroni river, Taki-taki is often used