Troubling research shows that many common animals in the United States are capable of contracting Ebola. With Ebola-infected sewage already introduced into the landfills and sewer systems of at least one major city, there is an unsettling possibility that wildlife could become infected with the deadly virus.
The story of Spanish Ebola patient Teresa Romero Ramos and the precautionary euthanasia of her dog has put a spotlight on the question of what animals can and can't contract Zaire-type Ebola. Monkeys, antelopes, fruit bats, porcupines, rodents, dogs, and pigs are all known to contract Ebola. However, different species react to the virus differently. In monkeys, Ebola is rapidly fatal. Horses and goats show mild or no symptoms, though they may be briefly contagious before they clear the virus from their systems.i Pigs show severe lung symptoms, and are quite contagious, spreading the virus short distances when they breathe.ii When dogs contract Ebola, they produce antibodies but display no symptoms of the disease. Whether or not infected dogs can pass the virus on to humans is unknown.iii
It's a doomsday scenario that harkens back to the days of the black death: rats carrying deadly plague from home to home. Thankfully, the history of this outbreak suggests that particular sensational scenario is extremely unlikely. Though diseased wildlife is responsible for initiating the current epidemic in West Africa, wildlife isn't known to spread Ebola between humans. Instead, the virus is spread almost exclusively by human-to-human contact.
Nonetheless, there is a less-extreme scenario that is within the realm of possibility. If Ebola finds a suitable animal host in the United States, the virus could be here to stay. Ebola could become endemic in the United States, and America could find itself in the same situation as Africa– experiencing a minor outbreak every few years. Ebola would become part of the American landscape, and every few years unlucky hunters, hikers, farmers, and pet owners could touch an infected animal and become sick.
This scenario is not too far fetched. There are already very small amounts of the virus escaping our hospitals and quarantines. Ebola victim Thomas Duncan spent two days in a Dallas apartment sweating and vomiting before being admitted to a hospital. This highly infectious waste all entered the Dallas sewers and landfills. An NBC film crew and Duncan's family are currently being quarantined, yet they are still depositing waste into public sewer systems. The potential risks are obvious in allowing this sewage to come into contact with sewer rodents before eventually being purified in wastewater treatment plants. Thankfully Ebola can't survive long in pure water, however the virus can survive for several days in body fluids such as feces, urine, and semen.iv
Even recent survivors could present a small risk of wildlife contagion. The CDC says Ebola can be found in semen for up to three months after recovery, and advises survivors to abstain from sex or use condoms for three months.iv This implies that recent Ebola survivors could still be releasing small amounts of the virus into sewers and landfills in their home states.
In the end, it all comes down to luck. It would take a series of very unlikely events for Ebola to travel from our sewage and trash all the way to a permanent animal host. But the more patients, quarantines, and survivors there are out there shedding the virus, the more likely this scenario becomes. It's important that health officials consider wildlife exposure when deciding on waste-disposal safety practices.
i Kudoyarova-Zubavichene, Sergeyev, et al. Preparation and Use of Hyperimmune Serum for Prophylaxis and Therapy of Ebola Virus Infections http://jid.oxfordjournals.org/...
ii Kobinger, Leung, et al. Replication, Pathogenicity, Shedding, and Transmission of Zaire ebolavirus in Pigs. http://jid.oxfordjournals.org/...
iii Allela, Bourry, et al. Ebola Virus Antibody Prevalence in Dogs and Human Risk http://wwwnc.cdc.gov/...
iv Centers for Disease Control and Prevention, Q&As on Transmission http://www.cdc.gov/...