District moots geo-mapping and sentinel surveillance

Aswin J Kumar | TNN | Apr 9, 2020, 04:24 IST

Thiruvananthapuram: The district, which has not recorded positive cases for the past six days and registered a 64% dip in persons under home isolation in the past one week, will initiate the second line of action employing geo-mapping and sentinel surveillance.
A sentinel surveillance system is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system, as per World Health Organization.
The health team will map the places where positive cases have been reported in the district. This will be followed by classification of areas as buffer zone and containment zone. Areas within 3km of occurrence of positive cases will be categorized as containment zone. The area beyond containment zone will be marked as buffer zone.
When the cases were reported, the health team had done an extensive screening of primary contacts who were identified during contact tracing in these areas. There were two cases in which number of primary contacts was very high and screening was done for a large number of contacts. As part of sentinel surveillance, the process will be repeated to ensure that there are no missing links.
The persons under high-risk category; those who had come in close contact with the person who was tested positive will also be screened to detect any late onset of symptoms. Persons with influenza like illness (ILI) in areas under containment zone and buffer zone will be screened in the second line of action.
As per WHO, whereas most passive surveillance systems receive data from as many health workers or health facilities as possible, a sentinel system deliberately involves only a limited network of carefully selected reporting sites. Data collected in a well-designed sentinel system can be used to signal trends, identify outbreaks and monitor the burden of disease in a community, providing a rapid, economical alternative to other surveillance methods.
Data collected from containment zones will be a key factor in understanding dynamics of transmission, especially in case of outbreak of disease in clusters; something which has not occurred in the capital so far.
District collector K Gopalakrishnan said that geo-mapping, which has been used mainly in areas where positive cases were recorded so far, will be used extensively from now on. “We have been regularly tracking trends in cases related to influenza like illness based on call service data, patients reporting at private and government hospitals and even from ambulance data. The symptoms of patients being picked up are being closely monitored. This will be extended across the district, especially in areas where cases have already emerged,” said Gopalakrishnan.
The district has so far had 388 primary contacts and 363 secondary contacts from various positive cases reported in the district. Road screening done by the team has also enabled to identify a positive patient who had landed in Chennai airport and then came via road to Neyyatinkara. He was taken to General Hospital and during the testing, his sample turned positive.
In the last one week, the district could bring down number of persons under home isolation from over 18,000 to below 7,000. The number of persons being hospitalized with symptoms has also decreased slightly in district.