With many(as much as 30%) having no symptoms they are infected the authorities may never figure out who brought the disease in. The contagious phase is also very short in humans and does not start as soon as a human is bitten or infected. Could have been a sailor making a hop from St. Martin to JVD. Could have been a air crew member who introduced the disease to mosquitos near any of the airports. A visitor for a two week sail or camping trip to JVD could easily get bitten at the airport and carry the disease to any number of island mosquito and then human populations.

The mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to ten days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. There is no way to tell if a mosquito is carrying the chikungunya virus. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of the virus to humans has not yet been defined.

"Infected humans are the main carriers and multipliers of the virus, and serving as a source of the virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for several days, at approximately the same time that they have chikungunya fever (see also clinical symptoms)."