33.4  Modes of transmission of diarrhoeal diseases

All three types of diarrhoeal diseases discussed so far are transmitted directly or indirectly by faeco-oral routes, as already described in detail in Study Session 32.

  • Briefly distinguish between direct and indirect modes of faeco-oral transmission of infectious agents.

  • Direct transmission occurs through contact between hands contaminated with faeces and the person’s mouth; indirect modes of transmission are through ingestion of contaminated food or water, contact with infected soil, utensils, etc., and transmission by flies that have crawled on faeces (Figure 33.4).

    Fly
    Figure 33.4  Flies are a major source of indirect transmission of diarrhoeal diseases. (Photo: CDC Image Library, image 5452)

The main modes of transmission for cholera, shigellosis and viral diarrhoeal diseases are summarised in Table 33.1 and Figure 33.5.

Table 33.1  Main modes of transmission for bacterial and viral diarrhoeal diseases.

Diarrhoeal diseaseMain modes of transmission
CholeraContaminated water or food (summarised in Figure 33.5)
Shigellosis (bacillary dysentery)Person-to-person contact, e.g. while caring for a sick person, or via contaminated water or food
Viral diarrhoeal diseasesContaminated water or food, particularly when feeding infants with milk or other nutritious fluids in a contaminated bottle
Main modes of transmission for most diarrhoeal diseases
Figure 33.5  The main modes of transmission for most diarrhoeal diseases are by ingestion of contaminated food and water. (Source: adapted from AMREF, 2007, Communicable Diseases Distance Education Programme, Unit 11)

33.3  Rotavirus infection and other viral diarrhoeal diseases

33.5  Diagnosis, treatment and control of bacterial and viral diarrhoeal diseases