A very long time ago, I was in Afghanistan speaking with a parasitologist from UC Berkeley. It seems that an unfortunate medical doctor in Eastern Iran had made the mistake of advising someone that there had been an outbreak of an epidemic. The doctor was severely beaten by Savak, the secret police. Such a disclosure would have discouraged tourism.
So, Ok, this is Saudi Arabia with billions of dollars -
As of 2010, about three million pilgrims participate in this annual pilgrimage. Crowd-control techniques have become critical, and because of the large numbers of people, many of the rituals have become more stylized. But even with the crowd control techniques, there are still many incidents during the Hajj, as pilgrims are trampled in a crush, or ramps collapse under the weight of the many visitors, causing hundreds of deaths.
The logic is simple. A person contracts the illness, but does not show signs in Saudi Arabia. He gets on the boat or plane, goes home and dies. No problem. He must have gotten the illness somewhere else, right?