Travellers have been warned about the resurgence of a disease spread by mosquitos with 'high risk' in 42 countries. The Foreign Office-backed Travel Health Pro website this week issued an alert over the virus spreading in parts of Africa, Central and South America, and in Trinidad in the Caribbean. Yellow Fever can cause a serious haemorrhagic illness that can be fatal for humans . Yellow fever vaccination and mosquito bite avoidance are important preventive measures against the disease,