I rather imagine that this doctor is much healthier in general than the patients he treats in Africa. Hoping, praying that his system can combat this monster.
According to articles I have read, a medical colleague in the U.S. he has been in touch with says he was “exhausted” when he contracted the virus. Sadly, the stress and the long hours he worked caring for his patients may make his immune system less able to fight the disease. He does need prayers.
My concern with the situation is with his family who was with him as recently as a few days before he became symptomatic. They are now back in Texas and are not quarantined. Word from Health Officials in Texas is that the virus is not contagious prior to the onset of symptoms. I am skeptical of this information as typically viruses are frequently contagious before symptoms occur... think of chicken pox for example. The incubation period is 2-21 days for Ebola. That leaves much time for his unfortunate family to interact with many people in Texas before they show symptoms. These people in turn could potentially interact with many more people... etc. This is how epidemics begin.
In my educated opinion, while it was and is a noble thing for this doctor to minister to the ill in Africa it was misguided for him not to send his family home once the outbreak began. In keeping them there with him, he may have inadvertently brought this virus to North America.