The novel H7N9 avian influenza strain that has emerged in recent weeks has infected more than 500 people and killed a little over 200. The severity of this strain in such a short time has led investigators to look into the evolution of the virus in a report published by Nature this past week.
What these investigators found was that the virus was initially detected in Shanghai late March of 2013. The cause was attributed to birds, leading to the closure of poultry markets. The quick response to the outbreak helped drastically decrease the incidence of the virus; however, months later, the virus returned, resulting in a second wave of human infections in the South of China.
Like other flu viruses, the virus was seen to have a winter seasonality.
As the virus spread South, it began to mutate - by the second wave, it had divided into three main branches that led researchers to draw conclusions about the spread of the virus in both human and avian populations.
The work of these researchers only reinforce the notion that careful surveillance of flu is necessary to containing outbreaks and preventing epidemics. While such surveillance requires both time and money, it is important to do so, especially for strains like H7N9 that are believed to have pandemic potential.