In the countries where wastewater treatment has improved, there has been a notable reduction in the incidence of diseases such as hepatitis, cholera and typhoid fever. It should come as no surprise, then, that coastal degradation and marine pollution are among the region's worst environmental problems. Population pressures, infrastructure development in general and coastal tourism in particular have done much harm to coastal and marine ecosystems. Coral reefs have also been badly affected. In the Caribbean, 61% of reefs are threatened by tourism pressure and pollution, among other factors.