Tracking Typhoid: How DNA and GPS Partner to Prevent Disease

Water pumps in Nepal. Image Source: Prince Roy

Water pumps in Nepal. Image Source: Prince Roy

Every year, Nepal witnesses thousands of cases of typhoid illness in Kathmandu. Although the disease is common, how it spreads isn’t completely understood. In an effort to better understand this concern, researchers with Oxford University Clinical Research Unit-Nepal (OUCRU-NP) have been tracking illness occurrences of typhoid strains Salmonella typhi and Salmonella paratyph.

Typhoid is believed to be a water-borne bacteria, but within that category there are many ways the disease may be spread: Person-to-person contact, unclean food in the home, unclean food vendors, or unfiltered water in public places such as schools. The results of this particular study reveal that the bacteria may cluster around public water spouts.

A similar course of discovery took place nearly two centuries ago in the 1840s, when John Snow used interviews, deductive reasoning, and a hand-drawn map to suggest that public pumps might be a key source of spreading cholera in London. Much has changed since Dr. Snow used mapping to investigate cholera hot spots. Today’s researchers share Snow’s goal of disease prevention, but an array of new tools and constantly developing theories of infection aid them in their work.

For the study on typhoid in Kathmandu, researchers took blood from 700 Kathmandu patients infected with typhoid. They used DNA sequencing to determine the strain’s genotype for each patient and mapped the patients’ home locations using GPS (Global Positioning System). Mapping shows that outbreaks tend to cluster around water spouts, as reported by SciDev.Net.

DNA data helps researchers to determine whether separate typhoid outbreaks are related to one another, which in turn allows for speculation as to how the disease may be spreading.

A stronger understanding of sources of disease allows health officials to take more effective action toward the prevention of disease. For example, the Kathmandu study suggests that environmental rather than person-to-person causes may be most responsible for the spread of typhus in Nepal.

If this study is supported by further evidence, then health officials may be able to diminish incidences of the disease by improving ground water quality. (Fecal contamination is suspected as a potential root of water spout transmitted typhus.) Because DNA allows for increased precision in disease tracking, researchers at OUCRU-NP hope that their typhus research may spawn similar studies of other threatening illnesses.