Infected once, immune from second attack

PUNE: There is a silver lining to the trauma and panic experienced by the 250-odd patients who have tested positive for the H1N1 flu. The National Institute of Virology (NIV) says that after recovering, these patients develop long-term immunity against the virus. Even if the virus turns virulent, these patients will not be infected again.

������The strain of the H1N1 virus is fairly mild at this stage and its clinical severity is like that of a seasonal flu,������ NIV director A C Mishra said. ������Those who get infected by the virus strain and recover develop an immunity against it. And if the strain become virulent and strikes back, those who have recovered will be safe.������

Microbiologist Siddhartha Dalvi said as the pandemic evolves, the H1N1 strain is bound to mutate and change its properties to a greater or lesser extent. ������But those who have already been exposed to this strain will be protected for a long duration even if the strain mutates, depending upon the genetic make-up of an individual,������ he said.

Even if there were to be a new pandemic with a different H1N1 strain after a few years, the population presently infected will still be at least partly protected, said Dalvi. H1N1 subtype is one of commonest subtypes causing recurring epidemics and pandemics over the years, he added.

Dalvi said, ������There are two types of immune responses - cell-mediated and antibody-mediated - that develop when a human being encounters a new pathogen. Both responses are developed in a person infected with the H1N1 virus strain, which results in long-lived resistance to chances of re-infection.������