Prevalence of cystic fibrosis
As with sickle cell anaemia, cystic fibrosis is a recessive genetic disorder.
Around 1 in 30 people are heterozygous carriers, i.e. they carry just a single copy of the mutant allele and do not exhibit symptoms.
A person with cystic fibrosis must have both copies of the mutant allele.
Cystic fibrosis carriers may have some resistance to cholera, but this has not been confirmed.
Cystic fibrosis is most common among European populations.