Specific Infectious Diseases of Public Health Concern

Escherichia coli (E. coli) is a bacterium commonly found in the gut. Some strains can cause serious food poisoning, leading to diarrhoea and sometimes to life-threatening complications including haemolytic uraemic syndrome (WHO, 2018a). 

Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world with around a billion cases of seasonal influenza annually, including 3–5 million cases of severe illness. It causes 290,000 to 650,000 respiratory deaths annually (adapted from WHO, 2025).

Smallpox is an acute contagious disease caused by the variola virus. Before its eradication, smallpox was one of the world’s most devastating diseases known and was fatal in up to 30% of cases (WHO, no date a).  

COVID-19 is an infectious disease caused by the SARS Coronavirus 2 (SARS-CoV-2), a virus first identified in human populations in late 2019 which caused a global outbreak of coronavirus – an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (adapted from WHO, 2023 and WHO Euro, no date).

Rabies is a serious public health problem in over 150 countries and territories. It is a viral zoonotic disease that affects the central nervous system and spreads from bites, licks, and scratches from infected mammals. It is almost always fatal when clinical signs appear, killing approximately 59,000 people every year (adapted from WHO, 2024a; and WOAH no date). 

Leptospirosis is an infectious disease caused by a pathogenic bacterium of the genus Leptospira. These bacteria called leptospires affect both humans and animals. Humans become infected through direct contact with the urine of infected animals or with a urine-contaminated environment which can lead to serious and sometimes fatal disease (adapted from WHO & ILS, 2003).

Varicella is an acute, highly contagious disease caused by varicella- zoster virus. Following infection, the virus remains latent in neural ganglia and in about 10-20% of cases it is reactivated to cause herpes zoster, or shingles, generally in persons over 50 years of age or immunocompromised individuals. (WHO, no date).

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Cholera is a global threat to public health (WHO, 2024a). 

Severe acute respiratory syndrome (SARS) is a viral respiratory illness caused by a coronavirus called SARS-associated coronavirus (SARS-CoV). Among individuals who meet the current WHO case definition for confirmed SARS, the case-fatality rate is approximately 9.6% (WHO, no date). 

Plague is caused by the bacteria Yersinia pestis, and can be a very severe disease in people, with a case-fatality ratio of 30% to 60% for the bubonic type and is always fatal for the pneumonic kind when left untreated (WHO, 2022).