The two strains had a common H1N1 - type ancestor, but both have been evolving independently in pig populations, and the minute changes to viral genes that allowed the virus to adapt to a new host were different in each strain. (scientificamerican.com)
The circumstances of the Nipah outbreak suggest that the virus needs a large pig population to maintain itself long enough to have a chance of spreading to humans. (discovermagazine.com)
The first priority will be given to Namwendwa because it has the highest pig population in the district. (globaleducationmagazine.com)