Outbreaks, Epidemics, and Pandemics Summary(Dr MI Week 10)

Outbreak Definitions

  • Outbreak/Incident:

    • Two or more people with similar illness linked by time or place.

    • Infection rate higher than usual background rate.

    • Single case of rare diseases (e.g., diphtheria, botulism).

  • Epidemic: Sudden increase in cases above normal expectations in a specific population/area; similar to outbreak but potentially larger geographically.

  • Pandemic: Epidemic occurring worldwide, crossing international boundaries, affecting many people.

Outbreak Investigation

  • Recognition:

    • Through UKHSA, local authorities, NHS, microbiologists, primary care, NOIDS.

  • Outbreak Control Team (OCT):

    • Formed when an outbreak declaration happens; includes microbiologists, medical clinicians and infection control nurses.

  • Data Collection:

    • Patient info: age, location, conditions, travel history.

    • Affects diagnostic testing.

    • Medical history is important.

  • NHS England regional monitoring teams use PHE data to predict service demand during seasonal outbreaks.

  • Surveillance helps the NHS identify rises in influenza, norovirus, and other acute seasonal illnesses.

Management of Outbreaks

  • Primary objective: protect public health by identifying the source and implementing control measures.

Surveillance

  • Global: WHO, CDC.

  • European: ECDC (e.g., measles cases in EU).

  • PHE/UKHSA:

    • Data from clinical microbiology labs.

    • Laboratory-confirmed cases (pathogen isolated from sample).

    • Mandatory surveillance requires labs to forward data on specific microbes.

Viral Outbreaks Examples

  • SARS-CoV-2003:

    • First severe and transmissible disease of the 21st century.

    • Over 8000 cases worldwide, 774 deaths, CL3 lab required.

  • Swine Flu Pandemic (2009-2010):

    • H1N1; First pandemic where the UK had a specific vaccine while the virus was still causing disease.

  • MERS-CoV:

    • First appeared in Saudi Arabia, circa 2012.

    • Approx 35% of patients died.

    • Camels are a major reservoir host.

  • Zika Virus:

    • Transmitted by mosquito; may cause birth defects during pregnancy.

Bacterial Outbreaks Examples

  • Cholera (Yemen):

    • Largest outbreak since records began (>1 million cases).

    • Caused by Vibrio cholerae.

  • Diphtheria (Yemen):

    • Transmitted by close contact; respiratory diphtheria is fatal.

  • Measles (Europe):

    • Outbreaks in France, Bulgaria, Italy, Poland and Romania.

  • Tuberculosis (Leicester):

    • Largest TB outbreak in the UK (2001).