verb
1
BAD : I'm doing the course to expand my job opportunities.
GOOD : I'm doing the course to increase my job opportunities.
◆◆◆
expand = become (or make something become) larger in size, area or activity: 'Metals expand when they are heated.' 'Within three years this small business had expanded into a chain of department stores.' increase = become (or make something become) larger in number, amount, cost, etc: 'Sales of new cars increased from 1.2 million in 1993 to 1.8 million in 1994.' 'By the year 2020 the government aims to increase the number of secondary schools by 50%.'
2
BAD : The epidemic began to expand rapidly.
GOOD : The epidemic began to spread rapidly.
◆◆◆
When you are talking about a disease, fire, war, social problem, feeling, etc, use spread : 'The army was called in to stop the riots from spreading.' 'Dissatisfaction with the present government seems to be spreading.'
3
BAD : The newspapers are not allowed to expand political ideas.
GOOD : The newspapers are not allowed to spread political ideas.
◆◆◆
When you are talking about news, information, ideas, etc, use spread : 'Within hours the news of the bank's collapse had spread all over the world.' 'I hope you haven't been spreading rumours.'