It is better if you do not. During very early stages of Chikungunya virus fever there is viremia. And some of the virus may be present in the breast milk though Chikungunya virus infection is acquired through mosquito bite and NOT through ingestion. As in newborns the immune system is not matured particularly monocyte-macrophages system, these cells may not be able to take care of the ingested virus absorbed through mucous membranes.