Two of the dead were children (aged 2-5 years), one from the city while another from North 24 Parganas district Principal Secretary (Health and Family Welfare) Moloy Dey said.
"Both the children were in critical condition and were fighting for life since being admitted to the hospital last month," Dey said.
The other two patients are women in their 60s, one from Hooghly district, he said.
"All the four patients were under ventilation since the day they were admitted. They had multiple-organ failure that led to their death. One of the two adults was having a cardiac problem while another was highly diabetic," Dey said.