Infectious Diseases

Vector-borne diseases encompass a variety of illnesses that are caused by the spread of pathogens by living organisms known as vectors. These infectious diseases can be transmitted via vectors among humans (e.g. malaria, dengue), among animals (e.g. African swine fever, East Coast fever), or from animals to humans (e.g. Nipah virus disease). Many of these vectors are bloodsucking insects, and mosquitoes are the best-known disease vectors.

Viral haemorrhagic fevers include a spectrum of relatively mild to severe life-threatening diseases characterized by sudden onset of muscle and joint pain, fever, bleeding and shock from loss of blood. In severe cases, one of the most prominent symptoms is bleeding, or haemorrhaging, from orifices and internal organs (WHO, no date a). 

Zoonotic diseases, or zoonoses, are diseases shared between animals – including livestock, wildlife, and pets – and people. They can pose serious risks to both animal and human health and may have far-reaching impacts on economies and livelihoods and represent a major public health problem. Zoonotic diseases are commonly spread at the human-animal-environment interface – where people and animals interact with each other in their shared environment (adapted from WHO, FAO, WOAH, 2019 & WHO, 2020). 

Diarrhoeal diseases are infectious diseases, contaminants and other causes of diarrhoea. Diarrhoea is defined as the passage of three or more loose or liquid stools per day, or more frequently than is normal for the individual. Diarrhoeal disease is the third leading cause of death in children 1–59 months of age. It is both preventable and treatable. (WHO, 2024a). 

Airborne transmission of infectious agents refers to the transmission of disease caused by the dissemination of very small droplets that remain infectious when suspended in air over long distances and time, and potentially cause significant morbidity and mortality (adapted from WHO, 2020). 

Cryptosporidium is a microscopic parasite that can live in water, food, soil, or on surfaces that have been contaminated with infected faeces and causes the watery diarrhoeal disease cryptosporidiosis (adapted from CDC 2024 and Peletz et al., 2013).

Bloodborne viruses are viruses transmitted by direct contact with infected blood or other body fluids (adapted from WHO, 2023). 

Cysticercosis is a preventable infection in humans and pigs caused by the larval stages of the parasite Taenia solium (pork tapeworm). Human cysticercosis can result in devastating effects when the larvae are located in the central nervous system, resulting in neurocysticercosis which may cause convulsions and epileptic seizures and can be fatal. It is the main cause of preventable epilepsy where the parasite is present, and it is estimated to affect between 2.56 and 8.30 million people (adapted from WHO, 2023). 

Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, hepatitis E, typhoid and polio (adapted from WHO, 2023a and WHO, 2023b). 

Foodborne diseases are caused by contamination of food and occur at any stage of the food production, delivery and consumption chain. They can result from several forms of environmental contamination including pollution in water, soil or air, as well as unsafe food storage and processing. Foodborne diseases encompass a wide range of illnesses from diarrhoea to cancers (WHO, no date a).