First pig-to-human transmission of Ebola-Reston virus

Abstract

Philippine authorities and internatinal agencies have confirmed that Ebola-Reston virus has likely been transmitted, for the first time, from pigs to human beings. The US Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) previously confirmed the first ever outbreak of the virus in pigs, and has now commenced initial testing on people. The CDC has confirmed that five people in contact with sick pigs have now tested positive for antibodies to the Ebola-Reston virus. Pierre Rollin (CDC Special Pathogens Branch), an expert on Ebola viruses who participated in a recent joint UN mission to the Philippines, said that the discovery of Ebola-Reston virus last year in pigs “was a discovery no one expected”. Initial testing by the US Department of Agriculture, after an increase in Philippine pig mortality, detected various expected viruses, including the arterivirus that causes porcine reproductive and respiratory syndrome (PRRS). However, the search also revealed Ebola-Reston, a distinct species of Ebola first identified after an outbreak a decade ago in non-human primates from the Philippines. Four farm workers and a slaughterhouse worker have tested antibody-positive out of 77 people in contact with the sick pigs. Similar to the previous outbreak, infected workers had no clinical signs of infection, except antibodies to the virus. However, Rollin told TLID that “no one can say something is non-pathogenic for humans with this small number of cases. We don't know what this virus is capable of doing to someone who is immunosuppressed or on immunosuppressive drugs”. Philippine authorities, with CDC support, will be following up the infected people and doing further animal and human testing. “Nobody understands the implications for animal health”, explains Rollin. Other viruses that exist in the pig population are known to cause disease in pigs. CDC is preparing laboratory studies to investigate the consequences of infecting pigs with Ebola-Reston and PRRS viruses, singly and together. Other experts have warned of the possibility that Ebola-Reston could mutate in susceptible people and become more transmissible. With new pathogens “there is always something we don't know”, says Rollin. “We must keep an open mind and not rule out anything”, he said. The joint UN mission was expected to issue recommendations on the outbreak as TLID went to press.