Ebola is a killer, but it is not very contagious and not a threat in the United States.
If you are not a health worker or, for some other reason, in direct physical contact with someone who has Ebola, you are not at risk of getting it. Here’s what we know:
While Ebola is deadly, it is not very contagious. The flu virus is carried through the air, but the Ebola virus is not. You have to be in physical contact with a sick person and get their blood or vomit or feces on your skin.
Even in areas of Africa where the outbreak is spreading out of control, each sick person infects only two others on average. That is called the R-nought value. It is a measure of how contagious a disease is. Compare it to measles, for example, which is airborne like the flu. The R-nought for measles is 18, meaning each sick person infects 18 others on average during an outbreak.
We’re seeing that system at work right now. Everyone who came in contact with Thomas Duncan, the only person to die of Ebola in this country, was tracked down and monitored for 21 days, which is the maximum incubation period for the virus. All of them have now been cleared of risk.
Duncan did infect two other people; nurses who cared for him in Dallas. So everyone they had contact with was also traced, and those people are also being monitored for 21 days.
But while Ebola is not very contagious, it is highly infectious. One drop of an infected person’s blood may hold a million virus particles, far more than most viral diseases. And you do not need to have a cut on your skin to become infected. It’s enough that the virus come in contact with skin.
That is why health workers treating Ebola patients must be gowned head to toe and must follow strict protocols when removing the contaminated garments. It is also why so many health workers in Africa have died.
Thomas Duncan was infected because he helped to carry a woman who was dying of Ebola to the hospital in Liberia. He also carried her back home when that hospital turned her away for lack of space. The two nurses who treated him in Dallas were apparently infected because their gowns left some skin exposed.
So what is your risk? We’re heading into the holiday shopping season. Should you worry about crowded shopping malls or public transportation? The short answer is no. Even if you find yourself on a crowded bus next to someone who seems sick, what you need to worry about is catching the flu, not Ebola.