NEW DELHI: Dengue cases crossed 1,500 in Delhi today where the worried civic authorities issued an ultimatum to the striking mosquito breeding checkers to return to work by tomorrow evening or face sacking.

"If the domestic breeding checkers do not return to work by 5 pm tomorrow, we will sack them and appoint new ones in their place," MCD Public Health Committee Chairman V K Monga said.

Officials, however, admit that that appointing new people may also lead to a temporary manpower crunch as the process may take at least four to five days. The strike by at least half of MCD's breeding checkers demanding regularisation of their contract jobs entered the fourth day today.

The striking workers staged a dharna and raised slogans near the MCD headquarters at Town Hall today. Anti-Malaria Karamchari Sangh president Ashok Chaudhary said the DBCs will continue their agitation. Officials said the workers want the MCD to assure in writing about their regularisation.

Monga said regular employees of MCD Public Health Department have volunteered to "work over-time" to help control dengue, which has caused more of a scare this time due to rapidly increasing cases. The authorities are concerned as the city will host the Commonwealth Games next month.

" The Health Employees Welfare Union will create public awareness with regard to prevention of dengue. The union will involve National Social Service ( NSS) workers of schools and colleges in this initiative," he said unveiling a leaflet published to educate public about the vector-borne disease.

"The health employees will organise public awareness rallies with residents welfare associations, social welfare organisations, the schools of Delhi government and MCD as well as private organisations on Saturdays, Sundays and in the evening after office hours," Monga said.

The national capital today reported 74 new dengue cases, taking the total number of patients to 1512. South Delhi continued to be worst-affected this season recording 252 cases, followed by MCD Central Zone (218) and Civil Lines (177). There were four dengue deaths this season.

Meanwhile, former Delhi Mayor Arti Mehra today urged Prime Minister Manmohan Singh to constitute a special dengue control task force in Delhi to place anti-dengue measures under one nodal head from the PMO thereby ensuring effective coordination among various agencies.

Mehra said that as the prestige of the nation is at stake and the situation appears to be getting out of control having ramifications on the upcoming Commonwealth Games, it would be appropriate if he immediately intervenes.

In a letter, she requested there is an urgent need for the intervention of the Central government. "As a responsible nation, which is hosting the Commonwealth Games, we have to ensure that the foreign guests are not exposed to the fear of dengue," she said.