36.5% of Delhi’s dengue caseload ‘untraceable’

According to the public health department’s latest dengue disease report, of the 570 dengue cases reported till Monday the MCD has classified 208 as “untraced”.

More than a third of the 570 dengue cases reported so far this year in Delhi remain “untraceable” because of incomplete or incorrect addresses, hampering efforts to identify disease clusters and contain outbreaks, municipal and health officials said on Wednesday.

The lack of traceability is significant as dengue was made a “notifiable disease” in Delhi five years ago under an effort to strengthen surveillance and enable targeted action. (Shutterstock)

The lack of traceability is significant as dengue was made a “notifiable disease” in Delhi five years ago under an effort to strengthen surveillance and enable targeted action

According to the public health department’s latest vector-borne disease report, of the 570 dengue cases reported till Monday, the Municipal Corporation of Delhi (MCD) has classified 208, or 36.5%, as “untraced” because of incomplete or incorrect addresses. Another 90 cases have been classified as infections acquired from other states.

This left only 272 cases, or 47.7% of the total, that can be geographically traced to locations within Delhi.

Faulty patient details hamper efforts to identify dengue clusters and contain outbreaks

A senior public health department official said the objective of bringing dengue under the Epidemic Diseases Act was being undermined by incomplete data submitted by health facilities.

“The reporting of cases has improved, but there is still a large number of cases where the addresses of patients are missing or incorrectly provided. In such cases, we are unable to trace the exact location of patients. This means clusters cannot be identified accurately and countermeasures end up being less targeted,” the official said.

West zone reports highest number of traceable dengue cases in Delhi

The geographical distribution of the 272 traceable cases shows that five were reported from New Delhi, 14 from Delhi Cantonment, seven from the Railways and 246 from MCD areas. Among the MCD zones, the West zone reported the highest number of cases at 43, followed by the Central zone with 34 and Shahdara North with 27.

The problem of untraced cases is not new. During the corresponding period last year, Delhi had reported 412 confirmed dengue cases, while 351 cases remained in other categories. In 2024, the city had reported 425 confirmed cases during the same period, while 424 remained in other categories.

An MCD official said identifying clusters was crucial to classifying areas as “hot spots” or “vulnerable” and triggering intensified surveillance and mosquito-control measures, including fogging, anti-larval work, spraying and information, education and communication (IEC) activities.

“If address tracing is flawed, the countermeasures are also affected,” the official said.

Expanded surveillance has increased reporting, but data gaps persist

Before dengue was notified under the Epidemic Diseases Act in October 2021, the public health department relied on a sentinel surveillance system, under which cases were reported mainly by major hospitals and healthcare facilities.

Under the system, 36 major hospitals shared weekly data on dengue, malaria and chikungunya with the malaria operations headquarters, a second civic official said.

“The number of units and clinics sharing disease data on the portal has gone up five to six times, but the data remains faulty, with a large proportion of cases not having a specific address or contact number of the patient,” the official said.

Ashok Bhasin, who heads North Delhi Residents Welfare Federation said that north Delhi area urgently needs larvicide and fogging drive. “The mosquito density is increasing as corporation has failed to check waterlogging. We have not seen any fogging drive in our area and claims of intensive drives are only on paper. On the other hand we have been struggling to get open sewer holes covered. There is total apathy from administration.”