Dengue reinfection cases up; more severe, say doctors

Pune: Doctors in the city are seeing a rise in dengue reinfection cases, generally more serious than the first time and requiring intensive care.

Dengue reinfection, or secondary dengue as known among medicos, is an infection with another dengue subtype in a person who has had a dengue infection in the past.

"At Ruby Hall, we are seeing cases with complicated dengue, those that have been referred to us from other centres. In the past month, we have come across cases with dengue hemophagocytic lymphohistiocytosis (HLH), an uncommon but severe complication of the infection. This is being seen in young patients getting secondary dengue," Dr Abhijit Lodha, consultant physician with Ruby Hall Clinic, told TOI.

There are four distinct serotypes of the dengue virus. A person infected with one serotype develops protective immunity against that strain, but not to the others.

Dr Urvi Shukla, chief intensivist at the Symbiosis University Hospital and Research Centre, told TOI, "We have treated a few secondary dengue patients this monsoon. Dengue is caused by the dengue virus, which is classified into four distinct serotypes [DEN-1, DEN-2, DEN-3 and DEN-4]. Each serotype represents a different subtype of the virus. Infection with one serotype does not provide immunity against the other serotypes. This lack of cross-protection between serotypes is a crucial factor that contributes to the risk of experiencing severe symptoms or complications during a second dengue infection."

She said the proportion of patients coming to the hospital with secondary dengue seemed to be slightly higher this monsoon than the same period last year.

The dengue cases and the prevalence of associated serotypes have been observed to exhibit a triennial pattern, with changes in dominant serotypes occurring approximately every three years.

"This pattern is a result of the cyclical nature of dengue transmission and viral dynamics. Cross-protective immunity against the four dengue serotypes tends to wane after 2-3 years. This means that the protective effect of immunity acquired from a previous dengue infection may decrease over time, leaving individuals susceptible to infections by different dengue serotypes," Dr Sanjay Pujari, director of the Institute of Infectious Diseases, said.

He said, "When individuals experience a dengue reinfection after their immunity has waned, they may be at risk of developing antibody-dependent enhancement, which can cause severe illness."