Any big gathering involving thousands of people from around the world — potentially swapping deadly microbes — always raises alarm bells for public health folks. And there is perhaps no larger gathering than the Hajj, the annual pilgrimage of roughly three million Muslims from all over the world to Mecca, Saudi Arabia.
In the past Hajj pilgrims have spread meningitis, tuberculosis, and polio — but six months into the world's biggest Ebola epidemic, governments are trying to keep them from getting the incurable virus.
The Saudi Ministry of Health last month banned Hajj visas for Sierra Leone, Guinea, and Liberia — the three nations most affected by Ebola this year with at least 5,800 cases.
Nigeria, which has been battling Ebola, was left out of that ban. It also happens to be one of the countries in the world with the highest concentration of Hajj pilgrims, according to data from the infectious-disease tracking website HealthMap.
There were only 20 Ebola cases in Nigeria (relatively few compared to the West African nations that are currently managing thousands), and the country reported last week that they have no suspected cases at the moment.
Several people were still under surveillance in Lagos and the southern oil city of Port Harcourt. If any of those people test positive, there's a slight chance they may have already infected others. However, the risk of bringing the disease to Mecca seems to be fairly remote. The southern part of Nigeria, where Lagos and Port Harcourt are located, is mostly Christian while the northern part of the country, which has not had any reported Ebola cases, is Muslim.
Still, Nigeria's proximity to a potential health disaster has the World Health Organization on alert.
Since September, the WHO has been briefing Hajj pilgrims on how to protect themselves from Ebola and putting them through health screening at the Lagos airport. Health officials have been taking the body temperature of pilgrims, as well getting their travel history and contact details.
In Saudi Arabia, pilgrims arriving at the King Abdulaziz International Airport airport near Mecca are also being screened for Ebola.
A Lagos State health official told South Africa's News24, "The idea behind the screening all passengers in and out of Nigeria is basically to make sure that Nigeria doesn't export any case to any country and at the same time we don't import any case."
The WHO is not recommending travel restrictions from Ebola-affected countries, but public health agencies like the Centers for Disease Control and Prevention suggest people from high-risk countries postpone Hajj travel.
Besides Ebola, health officials are also on alert for another deadly pathogen: Middle East respiratory syndrome coronavirus (MERS).
Cases in the Arabian Peninsula have increased rapidly in the past few months. The WHO and CDC suggest that, while the risk to Hajj pilgrims appears to be low, people with weakened immune systems or existing respiratory problems reconsider travel plans. They also suggest all travelers avoid contact with camels, believed to be the animal reservoir of the virus.