JOIN USEbola on airplanes, Ebola in sneezes
I’m flying soon. What is the risk of contracting Ebola on a flight?
Not high. Top Ebola experts have said they would not expect to be infected even if they were sitting next to another passenger with Ebola - unless that passenger actually vomited or bled on them. Patrick Sawyer, the Liberian-American who brought the virus to Nigeria in July, was so sick he had to be helped off the plane in Lagos. He had vomited while on board. There were about 200 passengers on the plane, according to Nigerian health authorities, and not one of them got infected.
Isn’t the virus airborne if a sneeze can move it 3 feet? What is the likelihood that Ebola will mutate into an airborne virus?
Although both the World Health Organisation and the Centres for Disease Control and Prevention take the position that Ebola is not transmitted through the air, scientists are publicly battling, on news websites and science websites, over whether it is possible in rare cases - or could become possible if the virus mutates.
Much has been made of two small studies in which the virus appeared to have passed through the air between monkey cages or between pigs and monkeys caged above them. It does appear, some scientists argued, as if prolonged exposure to airborne droplets under laboratory conditions might pass the disease. However, others argued that transmission might be an accident of cage cleaning, feeding or urine splashes.
Also, in 1989, 100 rhesus monkeys shipped from the Philippines to a government research lab in Reston, Virginia, started an outbreak of a variant of Ebola that does not harm humans. Ultimately, to stop the outbreak, all 600 monkeys in the building were killed. Some scientists who worked there believe the virus spread between cages and perhaps even between rooms when monkeys sneezed or coughed.
There are two kinds of airborne transmission. An infectious dose of measles, smallpox or chickenpox virus can be contained in a droplet small enough to hang in the air, so the next person to walk through that “sneeze cloud” catches it, or the disease transmits through ventilation systems. Influenza is thought to need bigger doses in larger droplets that fly as far as 6 feet but then fall to the floor.
No human airborne transmission of Ebola has been confirmed, even though there have been multiple outbreaks in Africa since 1976, and many crowded places - like minibus taxis - providing opportunities. If Ebola was transmitted like influenza, experts point out, an outbreak would echo the spread pattern of the 2009 flu pandemic, and by now there would be millions of cases around the globe. Ebola does not typically cause sneezing or coughing, and saliva does not normally build up large viral loads until late in the disease. But because patients can cough vomit or blood, or vomit violently, caregivers routinely wear masks and goggles.
No one can say exactly what the likelihood is that the virus will mutate to definitively become airborne, but it is not thought likely. No virus has ever been known to change its mode of transmission. HIV mutates incredibly rapidly - as much in one day as flu does in a year, according to CDC scientists - and HIV has not become airborne.
Since Ebola is good at finding hosts, it is under no great Darwinian pressure to change. On the contrary, since human Ebola victims die so fast that they can’t spread it to many others, the more likely change is for the virus to become milder so victims live longer. Airborne viruses have surface proteins that attach to cells in the nose and throat.
Imagine throwing magnetised BBs into a cast-iron pipe; all would stick. Ebola, lacking those proteins, is like marbles, falling down the pipe into the gut, where it attaches. It may take a lot of mutation to do the equivalent of changing a marble into a magnetic BB.
On pets getting Ebola
Can pets get Ebola? If so, which ones? What are the symptoms and treatment of Ebola in pets, and can pet owners get it from them?
Ebola is primarily an animal disease. Its natural reservoir is probably fruit bats, which can live with the virus without getting ill. Gorillas, chimpanzees and humans all die rapidly after getting infected.
Ebola is found in some hunted African animals, including forest antelopes and rodents. Pigs, guinea pigs, horses and goats have been infected experimentally and either had no symptoms or mild ones. Ebola has not been found in any African felines, such as lions, so cats may be immune.
Dogs living with humans apparently can get infected. Although the virus itself has not been found in dogs, antibodies have been detected in their blood, suggesting the dogs had survived infections. Gabon has had several Ebola outbreaks, and in 2005 French scientists tested 337 dogs for antibodies. Many were village strays that lived on what they caught and scraps that hunters threw them.
Villages in which there were both human deaths and hunters returning with infected bush meat - which often started the outbreaks - had the most dogs testing positive. The most likely explanation, the scientists said, was that the dogs were infected with the virus from meat scraps and from licking human vomit. They were not known to get ill.
Whether dogs can pass the virus to humans or to other dogs is unknown. Many diseases - including polio and typhoid - have silent human carriers who never get sick but pass fatal infections to others. Ebola is not known to exist in any North American animal species, including bats. But many species clearly could become carriers.
Since dogs interact intermittently with humans and with animals in city parks and rural forests, they could be a vector for transmitting Ebola from humans into wildlife, where it could, in theory, establish a permanent American reservoir.
While an infected dog could be quarantined, it would have to be caged indefinitely, since it is unknown how long it might remain infectious.