How ALS is Contracted
ALS is not a contagious disease that you "contract" or "catch" from others—it develops through a complex interaction of genetic susceptibility and environmental factors, with approximately 90% of cases being sporadic (occurring without known cause) and 10% being familial (inherited). 1
Understanding ALS Development
Sporadic ALS (90% of cases)
The vast majority of ALS cases arise without a clear genetic mutation or identifiable cause 1. The disease appears to result from:
- Gene-environment interactions: Multiple environmental risk factors acting together with genetic variants to trigger disease onset 1
- Unknown mechanisms: The precise pathophysiology remains unclear despite extensive research 2
Familial ALS (10% of cases)
When ALS runs in families, it follows an autosomal dominant inheritance pattern in most cases 2:
- C9orf72 gene mutations: Account for 40% of familial cases 2
- SOD1 gene mutations: Account for 20% of familial cases 2
- Over 60 genes identified: More than 20 major genes have been associated with ALS, with four genes explaining >50% of familial cases 3, 2
Environmental Risk Factors
While not "contagious," certain exposures may increase ALS risk 1:
- Early life factors: Being born and living in rural/country areas, younger parental age, lower educational attainment 4
- Occupational exposures: Welding and soldering, lead vapor inhalation, chemical exposures, electrical trauma 5, 6
- Nerve injury: May potentially initiate the disease process in susceptible individuals 7
Critical Clinical Point
ALS is neither infectious nor transmissible between people. It cannot be "caught" through contact, proximity, or any form of person-to-person transmission. The disease develops through a multistep pathway involving polygenetic variants combined with polyenvironmental risk factors acting over time 4.
For individuals with family history of ALS, genetic testing and counseling should be offered to identify at-risk carriers and provide appropriate support 1.