The Times of India recently reported that a number of people have been falling ill with what doctors have described as a likely new strain of dengue virus.
Doctors have said, of patients presenting with very similar symptoms, 1 in 10 have not been screening positive on the dengue virus Elisa test. Doctors believe that a mutation of dengue virus giving rise to a new strain may be what is causing the confusion. On the other hand, many other pathogenic infections cause systems similar to dengue fever. So, this new crop of patients may not have dengue virus to blame.
Sources: Times of India. http://timesofindia.indiatimes.com/city/bhopal/Not-dengue-but-vicious-virus-strain-hits-Bhopal/articleshow/54929875.cms