As an Indian I can tell you even a few infected people can come into the country and cause an outbreak here.<p>Its not like in US, the sewage infrastructure in India is very bad. There are open air sewage drains, mosquito infestation is every day life and in cities people live in very densely crowded homes. All of this contributes to a rapid spread in case of a outbreak.<p>In fact dengue outbreaks are common in India every summer, or a few months.