Cystic fibrosis is not contagious, which means that it is not possible to catch it from someone else. It is a genetic condition that occurs when both parents pass mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on to their child.
More than 30,000 people in the United States have cystic fibrosis (CF), while an estimated 10 million people are carriers. In carriers, only one copy of the CFTR gene contains mutations. People need two abnormal copies of the gene — one from each parent — to develop CF.
In this article, we discuss how genes play a role in cystic fibrosis. We also provide information on screening and testing for the condition.
Cystic fibrosis is a genetic disease, so faulty genes play a role in its development. Genes are small sections of the DNA on chromosomes inside each cell. Most cells in the human body contain 23 pairs of chromosomes.
The abnormal CFTR gene causes problems with how the body regulates chloride. In turn, this affects the cells that produce mucus, digestive fluids, and sweat.
If a child has CF, it means that they inherited the faulty CFTR gene from both parents. However, even if both parents have the CF gene, there is a chance that their child may not develop the disease.
If both parents carry the CF gene, their child has:
- a 25% chance of inheriting two abnormal genes and having CF
- a 50% chance of inheriting one abnormal gene and being a carrier
- a 25% chance of not inheriting either copy
Each child belonging to these parents has the same chance of inheriting the CFTR mutation, regardless of whether their siblings have CF or are carriers of the condition.
If a person with CF has children with a CF carrier, their children will either have CF or be CF carriers.
Although CF is not contagious, people with the disease have an increased risk of passing certain germs between them. Doctors refer to this as cross-infection.
CF causes a buildup of mucus in the lungs, which means that people with this condition are more prone to lung infections.
To lower the risk of cross-infection, doctors recommend that people with CF who spend time in the same area try to stay at least 6 feet apart because this is the distance that germs can travel when people sneeze or cough. Some people refer to this as the "6 foot rule."
People can also reduce the risk of spreading germs to others with CF by doing the following:
- keeping the hands clean
- covering the mouth when coughing
- getting all recommended vaccines
It is important to note that cross-infection only affects those with CF. People without this condition are not at increased risk of catching an illness from people with CF.
Cystic fibrosis symptoms vary in type and severity from one person to another. Some mutations of the CFTR gene cause more severe symptoms than others.
Possible symptoms include:
- frequent or chronic lung infections
- chronic sinus infections
- salty-tasting skin
- digestive issues, such as diarrhea or greasy or foul-smelling stools
- a persistent cough or coughing up blood
- poor growth
- nutritional deficiencies
- nasal polyps, which are growths in the nose
- rectal prolapse, where the lower intestine protrudes from the anus
People with CF may also develop CF-related diabetes and liver problems.
CF tests are now a part of newborn screening in all 50 U.S. states. As a result, most people with CF receive a diagnosis at birth.
Occasionally, CF results from a gene mutation that the newborn screening does not detect. In these cases, doctors usually diagnose CF before the child's second birthday when symptoms develop. It is also possible to test for CF during pregnancy.
There are two ways to check for CF in an unborn baby:
- Amniocentesis: testing of a sample of the amniotic fluid, which the doctor performs at 15–20 weeks of pregnancy.
- Chorionic villus sampling (CVS): testing a sample of tissue from the placenta, between weeks 10–13 of pregnancy.
Even if these tests determine that a child has CF, a doctor cannot use the results to predict the severity of the symptoms.
People can also choose to have a blood test to check for the CF gene. Some people opt to do so before they start a family, especially if they have a relative with CF or believe that they may be a carrier.
Testing after birth
If a person presents with chronic lung infections or other symptoms that could relate to CF, a doctor may recommend CF testing.
The standard test for CF is the sweat test. It involves collecting sweat and testing it for the presence of chloride. A person will only receive a CF diagnosis if they have two separate tests that show consistently high levels of chloride.
Individuals should speak to their doctor if they or a child in their care has symptoms of cystic fibrosis. A doctor can perform a physical examination of the individual and review their medical and family history.
People who have a close relative with CF and want to start a family may wish to speak to their doctor about genetic testing.
The doctor can do a simple blood test before pregnancy or use other methods during pregnancy.
Cystic fibrosis is not contagious — it is a genetic condition that a person inherits from their parents. It causes symptoms that affect the lungs and digestive system, and it also increases the risk of health complications, such as diabetes and liver disease.
Sometimes, parents may feel guilty that their child was born with CF. However, they should not feel responsible as the disease occurs due to a genetic mutation. Most people are not even aware that they carry this faulty gene.
People who wish to test for CF should speak to their doctor about it. It may also be helpful to see a genetic counselor to understand exactly what the test results mean.