An official in the Health Ministry says another Sierra Leonean doctor has been infected with Ebola, yet another blow to his country's fragile health system.

Ebola has infected more than 15,000 people, the majority of them in West Africa, and a higher number of health workers than in any previous outbreak. That has made responding to the epidemic even more difficult in countries that had too few health workers to begin with.

Abass Kamara of the Health Ministry said Tuesday that Dr. Aiah Solomon Konoyeima tested positive for the dreaded disease a day earlier. Konoyeima is a doctor at a children's hospital in the capital of Freetown and has been admitted to an Ebola treatment center in the city.

Ebola has infected more than 500 health workers in this outbreak.