import re
text1 = "The disease has spread to three countries: Guinea, Guinea-Bassau and Equatorial Guinea."
text2 = "Only Guinea-Bassau and Equatorial Guinea contained strains of the virus."
list_of_countries = ['Guinea', 'Guinea-Bassau', 'Equatorial Guinea']
list_of_countries=sorted(list_of_countries,key=len,reverse=True)

rx=r'\b(?:{})\b'.format("|".join(list_of_countries))
print(re.findall(rx, text1))
print(re.findall(rx, text2))