The dengue virus can infect several times, with each subsequent infection being deadlier than the one before, a new research from University of Cambridge says.
For decades, scientists have believed that the mosquito-borne disease infects a person only four times because there are four genetically distinct serotypes (viral strains) -- 1, 2, 3 and 4 -- of the dengue virus.
The findings come at a time when Delhi is battling its worst dengue outbreak in five years that has left 18 people dead. Latest official figures released on Monday put the number of cases at 1,872 amid allegations of underreporting.
The virus' antigenic properties -- the "coats" they wear to evade the immune system – is what makes multiple infections possible and deadlier, a global consortium of laboratories announced on Friday.
Scientists found significant antigenic differences within each dengue serotype, which means a person infected with one viral strain will not develop immunity against antigenically different viruses of the same type.
This explains why the first dengue infection is often milder than subsequent ones. Kapila Somani (name changed on request), 38, experienced it firsthand when she was diagnosed with dengue in August and took more than four weeks to recover. The Defence Colony-resident first had dengue two years ago.
“It was a lot worse this time. Two years ago, I recovered in a week, but it took me a month this year. Though I recovered two weeks ago, I still feel drained by the end of the day,” she said.
Doctors treating dengue patients, especially children, also say people need to be more careful if they are diagnosed with dengue the second time.
“It is easier to recover from dengue if you’ve been infected the first time. The second time, the response of the antibodies is more robust, which can aggravate symptoms and make you feel sicker,” said Dr NK Dubey, head of the department of paediatrics at Dr Ram Manohar Lohia Hospital.
Indian Medical Association secretary-general Dr KK Aggarwal said a patient was susceptible to heavy internal bleeding if infected twice with dengue. “Therefore, it’s important to tell your doctor if you’ve had dengue before, and to increase fluid intake --- 1-1.5 litres within 30 minutes of diagnosis and subsequently 150ml per hour.”
Transmitted by the bite of female mosquitoes that breed in containers with clear and stagnant water, dengue is characterised by high fever, severe pain and nausea.