The existence of two strains of the dengue virus — Type I and Type II — was verified by serotyping of samples tested positive for dengue in Delhi. The first produces dengue fever, whereas the second causes hemorrhagic fever and shock.
The other two categories are III, which causes a fever without shock, and IV, which causes a fever with shock or deep shock.
The Type II strain’s existence has sparked considerable alarm. Officials with the Union Health Ministry’s National Vector Borne Disease Control Program (NVBDCP) stated there was no need to be concerned.
“Type I, which causes milder symptoms, is predominant. Only a few samples have been found to be positive for Type II strain,” said an official.
Dengue has been a major public health concern in the city with recurrent outbreaks, prompting a rush to hospitals particularly in the post-monsoon period when mosquito breeding is at its peak.
An NVBDCP official said the serotyping results were preliminary in nature due to the small sample size. “We plan to have more tests to identify the trend so that clinicians are notified in advance about the strains in circulation,” she added. Uttar Pradesh, where febrile illness has claimed the lives of several children over the past few weeks, has also been found to have Type I and II strains of the dengue virus.
Dr Neeraj Nischal, additional professor of medicine, AIIMS, said the type of strain of dengue virus that is in circulation is important to prepare for a potential crisis. However, he added, it was more important to focus on preventing the spread of the disease itself by checking mosquito-breeding.
Nischal said people needed to ensure there was no stagnation of water in such places. The authorities need to make fighting dengue a social movement through public awareness, timely identification of high-risk zones and use of anti-larval spraying, among others, he added.
The latest data collated and shared by the municipal corporations on mosquito-borne diseases in the capital show 158 confirmed cases of dengue on September 11. This is higher than the number of cases of the viral illness reported in the same period last year. At least 68 cases of malaria and 40 of chikungunya — two other mosquito-borne diseases — have also been confirmed.
Said Nischal, “This is a worrying trend and urgent action is needed to prevent a full-blown crisis. We are in the middle of a pandemic caused by the novel coronavirus and another disease outbreak at this time may increase the load of the already stressed health services.
Dr Vinay Aggarwal, chairman, Pushpanjali Medical Centre, east Delhi, said there seemed to be more cases of dengue than of Covid at the moment. At Lok Nayak Hospital too, medical director Dr Suresh Kumar reported a significant surge in cases of dengue. “New admissions due to Covid have gone down. But there is a big increase in cases of febrile illness that are testing positive for dengue. Some patients have required admission,” Kumar said.