As early as 2007, an increase in pig mortality in swine farms in the provinces of Nueva Ecija and the Bulacan occurred. This prompted the government to initiate laboratory investigations on sick pigs and samples wre sent to international reference laboratories. In October 2008, results confirmed that the pigs were infected with the highly virulent strain of Porcine Reproductive and Respiratory Syndrome as well as the Ebola Reston virus (ERV).

In January 2009, a Joint Mission composed of animal and human experts from the Food and Agriculture Organization, the World organization for Animal Health, World Health Organization and the Departments of Agriculture and Health carried out a full risk assessment of the ERV situation quarantined farms in Bulacan and Pangasinan. In February, upon the recommendation of the experts, the depopulation of pigs was done in affected farms to prevent the further spread of the virus.

The DOH enjoined the local governments, the hog industry and the public in the four lines of defense – 1) report unusual occurrences of sick or dying pigs to local agriculture authorities; 2) adopt security measures to prevent and obtain outbreaks in pig farms; 3) prevent the entry of double-dead meat into the market; and 4) thorough cooking of pork and pork products by the public.