Spike in vector-borne disease cases despite intensified surveillance 

Despite the Pune Municipal Corporation’s (PMC) intensified surveillance, the city has reported a sharp spike in vector-borne disease cases like Chikungunya, Dengue and Zika virus. The PMC has attributed the surge to the change in virus trends and favourable breeding conditions for the vector. This year, the PMC Health Department has reported as many as 100 cases of Zika virus, 251 cases of Dengue and 225 cases of chikungunya respectively. PMC this year started surveillance and containment activities for vector-borne diseases even after suspected cases were reported, unlike after confirmed cases. 

Furthermore, the civic body also intensified vector-borne disease surveillance and containment after the guidance of experts from the National Institute of Virology (NIV), National Center for Vector Borne Diseases Control (NCVBDC)- Ministry of Health and Family Welfare (MoHFW) and state health department. However, the city has still witnessed a sharp spike in the cases, most of them in August and September. 

Dr Rajesh Dighe, assistant health officer and head of the vector-borne disease control programme, said, the reason behind the surge in cases is the virus trend we have observed especially in chikungunya cases.  

“The vector-borne disease virus reportedly mutates changes after a decade, like antigenic drift or shift. This we have witnessed when it comes to the chikungunya virus cases reported in the city. However, once the community develops immunity towards the infection gradually the number of cases starts to decline,” he said. 

Dr Dighe also added that the torrential and erratic rainfall this year is also another significant reason behind the sharp spike in cases, providing favourable breeding conditions. 

Dr Devashish Desai, consultant of infectious diseases at Ruby Hall Clinic, Pune, said, chikungunya outbreaks are witnessed to be reported every 5 to 6 years.  

“Outbreaks are reported after 5 to 6 years when the herd immunity in the community wanes out and the virus mutates. The spike is not just limited to Pune, but the entire country has witnessed a surge in Chikungunya cases,” he said. 

Dr Raman Gaikwad, infectious diseases physician, Sahyadri Hospital, said while the city faces yearly vector-borne outbreaks, this year appears to be a much larger epidemic.  

“The increased ICU admissions and severe cases, including complications like encephalitis, further underline the intensity of this year’s outbreak. The favourable climatic conditions, such as increased rainfall, undoubtedly enhance mosquito breeding, we have not seen any evidence to suggest a change in the Chikungunya virus strain.”