Epidemiology & Risk Factors

Strongyloides is known to exist on all continents except for Antarctica, but it is most common in the tropics, subtropics, and in warm temperate regions. The global prevalence of Strongyloides infection is unknown, but experts estimate that there are between 30–100 million infected persons worldwide.

In the United States, a series of small studies in select populations have shown that between 0–6.1% of persons sampled were infected. Studies in immigrant populations have shown a much higher percentage of infected persons ranging from 0–46.1%.

Strongyloides infection is found more frequently in the socioeconomically disadvantaged, in institutionalized populations, and in rural areas. It is often associated with agricultural activities.

The most common way of becoming infected with Strongyloides is by contacting soil that is contaminated with Strongyloides larvae. Therefore, activities that increase contact with the soil increase the risk of becoming infected, such as

  • Walking with bare feet
  • Contact with human waste or sewage
  • Occupations that increase contact with contaminated soil such as farming and coal mining

Furthermore, many studies have shown an association with Strongyloides and infection with Human T-Cell Lymphotropic Virus-1 (HTLV-1). These studies have shown that people infected with HTLV-1 are more likely to become infected with Strongyloides, and that once infected, are more likely to develop severe cases of strongyloidiasis.

Of note, HIV/AIDS infection has not been shown to be a risk factor for acquiring strongyloidiasis or having a worse clinical course.

Page last reviewed: December 31, 2018