Dengue scare: Why second infection is deadlier; know how symptoms change in case of reinfection

As dengue cases rise rapidly across many parts of the country and Delhi witnesses a remarkable surge in people suffering from the disease, it's time to follow all precautions, even if you have recovered from dengue in the recent or distant past. Unlike many viral infections, dengue virus (DENV) can be deadlier for you in case of repeat infection. While a person who has recovered from a particular serotype of dengue stays protected from the infection from all serotypes of dengue for 2-3 months, after this brief window, the protection wanes and the person can get infected by the rest of the serotypes. There are four serotypes of dengue currently - DENV-1, DENV-2, DENV-3 and DENV-4. (Also read: Dengue during pregnancy can turn fatal; know complications, symptoms and prevention tips)

This behaviour of dengue virus may seem peculiar at first glance as usually with other viral infections including Covid, the body remembers the infection for a long time through its memory B cells and memory T cells. However, in case of dengue the body only remembers infection from the serotype that caused infection and provides immunity only against that particular strain. When infected with other serotypes, the symptoms of dengue can become worse, antibodies from the primary infection may help spread the dengue viral infection.

Why people get second dengue infection

"The risk of getting a second dengue infection is as common as the first one because it occurs due to vector-borne disease and mosquito bites. It is all a matter of destiny that somebody experiences a second dengue attack, which happens because of the second mosquito bite. However, the course and clinical presentation of the disease can change the incubation period, which is generally 3 to 8 days but can shorten to as little as one day to three days. This means that the symptoms may start as early as one day after the mosquito bite and reach their maximum within five days," says Dr Anantha Padmanabha, consultant, internal medicine, Fortis Hospital, Nagarbhavi, Bengaluru.

Why severity of second attack is greater

"Dengue virus, which belongs to the Flaviviridae family, consists of four distinct serotypes, namely DEN-1, DEN-2, DEN-3, and DEN-4. After the first infection, individuals develop specific antibodies targeting the infecting serotype. When encountering a different serotype during a subsequent infection, these pre-existing antibodies can interact with the new virus particles in a phenomenon called ADE. During ADE, the antibodies generated against the first dengue serotype bind to the new virus particles but fail to neutralize them effectively. Instead, the virus-antibody complexes are taken up by immune cells through Fc receptors, which can lead to increased viral replication. This process potentiates viral infection, triggering a more robust immune response characterized by excessive cytokine release and activation of immune cells. Consequently, this heightened immune response can result in severe dengue symptoms, such as haemorrhage, organ failure, and shock," says Dr Hyacinth Peninnah Paljor, Senior Consultant, Dept of Internal Medicine, Amrita Hospital, Faridabad.

"The severity of a dengue infection can be higher when people experience a second attack because preformed antibodies are already present in the patient from their previous exposure to the dengue virus. As a result, the antibody levels peak early, and the platelet count may decrease significantly in a short period during a fresh dengue infection. Normally, platelet levels may decline around the fifth or fourth day and continue to decrease for 7-8 days before starting to recover. However, in the case of a second attack within one year of the first dengue infection, the platelet count falls rapidly, and there is a higher risk of developing a dreaded complication known as dengue shock syndrome (DSS)," adds Dr Padmanabha.

"Several factors contribute to the increased risk of severe dengue in individuals experiencing a second infection. First, the presence of cross-reactive but non-neutralizing antibodies from the previous infection enables ADE to occur. Second, the sequence of dengue virus serotypes to which an individual is exposed can influence the severity of subsequent infections. For instance, sequential infections with DEN-2 followed by DEN-3 or DEN-4 have been associated with a higher risk of severe dengue," says Dr Paljor.

DSS can occur more often in individuals who experience a second dengue attack within one year of the first one. In this condition, they may experience bleeding throughout the body, a drop in blood pressure, and even bleeding in the intra-abdominal and cerebral regions, meaning in the brain. This is a serious complication that can arise due to dengue shock syndrome.

How to prevent second infection

"Given the increased risk of severe dengue in individuals with a second infection, prevention and control strategies become crucial. Vector control measures, such as eliminating mosquito breeding sites and using insecticides, remain vital in reducing dengue transmission. Additionally, public health efforts should focus on raising awareness about the risks associated with sequential dengue infections and the importance of seeking medical attention promptly when symptoms arise," says Dr Paljor.