The World Health Organisation says the incidence of chikungunya in Tonga, which reached an estimated 10,000 cases at its peak, is now in decline.
WHO Epidemiologist Eric Nilles says a number of factors have contributed to the decline, including removal of breeding sites for mosquitoes and a growing immunity base.
He says when a sufficient proportion of the population has been exposed and built up immunity it is very hard for the disease to continue transmission.
Dr Nilles says it is unclear when Samoa and American Samoa, which are currently suffering from an outbreak of chikungunya, might see a decline.
"Many different factors including types of mosquito vectors and the density of the mosquito vectors and it's dependent again on a number of vectors, mostly weather related, so unfortunately it's quite difficult to make firm and reliable predictions."
Dr Eric Nilles