A few years ago, the Seal Centre set up a rescue centre in a former aquarium in Nouadhibou, a coastal town in Mauritania, not far from the caves where the monk seal pups are born. Until recently, one of the most important populations of monk seals - an estimated 270 animals - lived in this spot where the Sahara "falls into the sea". Unfortunately, a morbilli virus struck here in 1997 and one third to three quarters of the animals died. Scientist Prof. Ab Oosterhaus of the Erasmus University in Rotterdam and one of the advisors of the Seal Centre discovered the virus in several dead animals that Lies Vedder, the Centre's vet had performed an autopsy on. Carers from the Seal Centre and their Mauritanian counterparts looked after four monk seal pups that had lost their mothers because of the virus. Luckily, these animals recovered their health and could be released in September 1997 after being vaccinated against the virus. It is not yet known if and how the seal population will be able to recover from this disaster.