How many people have worms?
Intestinal roundworms are silent devastators of children and humanity. You can’t always tell from the outside if someone is infected and the effects silently accumulate over time as children grow up physically and mentally stunted and as the immune system gets weaker.
How many people in the world are infected with intestinal roundworms? The simple answer: ENORMOUS NUMBERS! Some estimates are as many as 2.3 billion (that’s one out of every three people and just under double the combined populations of North America and Europe). More people are infected than is almost possible to imagine and much more than any other parasite.
It’s hard to get a solid estimate as many of the people infected are the poorest and least accessible and as our techniques to diagnose people are primitive. In addition, the technique used for diagnosis has low sensitivity in general and is especially poor for hookworm diagnosis as the eggs collapse quickly on microscope slides1. Threadworms (Strongyloides) are also difficult to diagnose, and this parasite is likely underestimated2.
Given these challenges, estimates vary. The table below gives low and high estimates.
How many children have intestinal roundworms?
According to de Silva et al. children 14 years and under make up 33% of giant roundworm infections, 26% of whipworm infections, and 21% of hookworm infections. Many hundreds of millions of children are infected— according to their numbers 400,000,000 children have giant roundworms alone! Hall et al. 20084 go on to estimate that of children between ages 5-9 years, 61.1% are infected by at least one intestinal roundworm parasite in Africa region E (e.g. Ethiopia, South Africa), 64.3% in South-east Asia region B (e.g. Indonesia, Thailand), and 63.3% in Americas region D (e.g. Bolivia, Peru). Truly staggering and sobering numbers!!
Countries where intestinal roundworms are a public health problem.
1 Discussed in Habtamu et al., Parasitololgy International 60(2011): 398-402.
2 Montes et al., Current Opinion in Infectious Diseases 23(2010): 500-504.
3 Lower estimates for intestinal roundworms from Fenwick, Public Health 126(2012): 233-236. Higher estimate for intestinal roundworms according to World Health Organization, from de Silva et al., Trends in Parasitology 19(2003): 547-551. Threadworm estimate from Montes et al. Diabetes estimate WHO fact sheet August 2011 (http://www.who.int/mediacentre/factsheets/fs312/en/) . Malaria estimate from WHO fact sheet as of 2011 (http://www.who.int/mediacentre/factsheets/fs094/en/). HIV estimate from UNAIDS, as of end of 2010. Cancer estimates from World Cancer Research Fund International as of 2008 (http://www.wcrf.org/cancer_statistics/world_cancer_statistics.php).
4 Hall et al., Maternal and Child Nutrition 4(2008): 118-236.