Section 2: Biological Hazards

Section 2: Biological HazardsPreviewObjectivesThe Environments Role in DiseaseWaterborne DiseaseCholeraMalariaAntibiotic ResistanceEmerging VirusesCross-Species TransferObjectivesExplain why the environment is an important factor in the spread of cholera.List two changes to the environment that can lead to the spread of infectious diseases.Explain what scientists mean when they say that certain viruses are emerging.

The Environments Role in DiseaseNot all all damage to human health by the environment is due to toxic chemicals but by organisms that carry disease. Infectious diseases caused by pathogensPathogen - a virus or microorganism that causes diseaseCan be spread airborne from person to person or waterborne

The Worlds Most Infectious Diseases

Secondary Host Other diseases are transmitted by a secondary hostSecondary host - organism that harbors a parasite Vector - intermediate host that transfers pathogen or parasite to host Ex: Secondary host = human, parasite = malaria, vector = mosquito http://www.hhmi.org/biointeractive/malaria-mosquito-host

Malaria on the March

No vaccine for malaria but can be cured if treated promptly and correctly More common in tropical areas (near the equator) mosquitoes like that environment Waterborne DiseasesIllnesses caused by drinking water contaminated by human or animal feces Ex: Cholera, hepatitis A, salmonella, typhoid fever, e. coli About three-fourths of infectious disease are transmitted through water

CholeraIntestinal infection caused by drinking contaminated water that contains the bacterium Vibrio cholerae Causes diarrhea and vomiting quickly leads to severe dehydration and death without proper treatment Causes most of the infant mortality around the world

Antibiotic ResistanceAntibiotic resistance - resistance of a microorganism to an antimicrobial drug that was originally effective for treatments of infections caused by itThreatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses, and fungi

Emerging VirusesEmerging viruses - newly discovered viruses, one that is increasing in incidence or with the potential to increase incidenceEx: hantavirus, ebola virus, the West Nile virus, and the HIV (which causes AIDS) Most viral diseases spread directly from one person to another Often, the virus invades the body through a cut or through mucous membranes

Emerging VirusesWe do not have many effective drugs to treat viral diseases.Our main defense against viral diseases is vaccination.However, vaccines are virus specific and viruses evolve rapidly.New vaccines must be developed when a new strain of a viral pathogen evolves.

Cross-Species TransferLately, there has been an increasing number of pathogens that have made a cross-species transfer, or have moved from one species to another. These pathogens have lived for centuries in some species of wild animals and have often done little damage.Ex: HIV, West Nile virus