ISLAMABAD: Normally, our body is well equipped to deal with influenza; our immune system can ward off infections, causing no more than a few days of discomfort. However, once every few decades, a new strain of rapidly spreading influenza emerges.
New research suggests that should such a pandemic occur, we may be able to predict our chances of survival based on the year we were born in and the flu we were exposed to as children. The 1918 flu pandemic killed over 20 million people, more than twice the number of people killed in the First World War. In the United States, the estimated death toll was 675,000, according to the Centers for Disease Control and Prevention (CDC).
More recently, H5N1 and H7N9have caused the highest number of flu-related illness and death worldwide, the CDC report. In May 2013, the World Health Organization (WHO) reported 131 human cases of H7N9 influenza, of which 24 resulted in death.
The Asian H5N1 was first diagnosed in the Americas in Canada in January 2014. Although human cases are very rare, when they have occurred, about 60 percent of them ended in death.
Both of these viruses have caused severe respiratory problems, such as pneumonia and respiratory failure.
Until now, scientists thought that the virus you were exposed to as a child was irrelevant in predicting immunity to viruses that are transmitted from animals to humans.
New research – published in the journal Science – suggests that, on the contrary, the kind of flu virus we are exposed to as children predicts what avian-origin flu virus we will be protected from later in life.
Researchers from the University of Arizona in Tucson, in collaboration with the University of California-Los Angeles, examined two types of “bird flu” viruses, H5N1 and H7N9. Both of these strands have caused severe illness and death in humans, and they have the potential of spreading very quickly from animals to humans and among human hosts.
When someone gets a flu virus for the first time, the body produces antibodies that target hemagglutinin.
Hemagglutinin is the reason why a flu virus can spread so quickly. It is a protein that sticks out from the surface of the virus, targeting, attacking, and clumping together red cells. The name “hemagglutinin” refers to this protein’s ability to agglutinate red blood cells.
Virus types differ according to the type of hemagglutinin they have. There are only two main types of hemagglutinin and each of the 18 known types of influenza A virus falls into one of these two types.
One type of influenza virus includes human H1 and H2 viruses, as well as the avian H5 virus, and the other includes human H3 and avian H7.
Michael Worobey, the head of the Department of Ecology and Evolutionary Biology at the University of Arizona and senior author of the study, explains their results with the help of an analogy.
Say the two types of hemagglutinin are like two different flavors of a lollipop, he suggests.