Chennai: The Directorate of Public Health, along with WHO, has initiated a lab-based sentinel survey to determine the prevalence of typhoid in the city. The results will help the authorities decide whether interventions, such as vaccines, are required.
Typhoid fever, caused by Salmonella Typhi bacteria, spreads through contaminated food and water, with symptoms such as prolonged fever, fatigue, and abdominal issues. “The estimated incidence of typhoid is 1,000 out of every one lakh people in urban areas like Chennai. Studies have suggested it could be higher, up to 1,200 or 1,500. This could be an underestimate because not many doctors do the gold standard tests to confirm the diagnosis. Even when it is done, not all cases are notified by hospitals and labs,” said director of public health Dr T S Selvavinayagam. “The survey will give us the estimate and help in making policy decisions about the need for a vaccine.”

On Tuesday, the DPH organised a workshop to roll out the lab-based sentinel survey in which three govt hospitals and three private hospitals will send samples to the public health department for the survey. Blood samples of children aged between five months and 15 days, with more than three days of fever and no respiratory complaints, will be sent to the state public health laboratory. While doctors will continue to test and treat patients for the disease, additional samples will be sent to the state lab, he said. The labs will collect samples and test them for a year from the second week of May, he said.
In densely populated cities, the quality and safety of various water sources are crucial in disease transmission. Residents rely on various sources, including piped Metrowater supply, wells and borewells, private water tankers, and packaged water. Contamination occurs at various points, said Kanchi Kamakoti Childs Trust Hospital medical director Dr Janani Shankar. “Sometimes it’s the contamination in the water purifiers that causes the disease.”
The survey will be part of the multi-state study conducted at 18 sites by Union health ministry. A typhoid surveillance group constituted by the Union ministry planned a city-based lab-supported sentinel surveillance with support from WHO to explore the strategy for the introduction of the typhoid vaccine. In Tamil Nadu, Chennai (State public health laboratory) and Vellore (CMC) have been selected to carry out the survey.