C9

Exposure to contaminated drinking or recreational water is a significant cause of human illness.
Climate change acts as a driver for increased disease risk through several environmental shifts:
- Sustained increases in global and local temperatures.
- A higher frequency of heavy rainfall and subsequent agricultural or urban runoff.
- The physical and biological effects of major storms and hurricanes.
The health impacts resulting from these environmental factors include:
- Gastrointestinal illnesses, with diarrhea being a primary symptom.
- Pathological effects on the human nervous and respiratory systems.
- Chronic or acute damage to the liver and kidneys.

Climate-related impacts influence human exposure to various biological and chemical hazards:
- Pathogens such as bacteria, viruses, and parasites, specifically including $Cryptosporidium$ and $Giardia$ .
- Toxins produced by harmful algal blooms and cyanobacterial blooms in water sources.
- Chemicals introduced into water systems from diverse human activities.
Changing water temperatures significantly alter the behavior and presence of these agents:
- Waterborne $Vibrio$ bacteria and harmful algal toxins may appear at different times of the year than previously recorded.
- These threats are now emerging in geographic locations where they were not considered a threat in the past.
- Toxins may be encountered directly in the water or through the consumption of seafood.

Increases in extreme precipitation, hurricanes, and storm surges lead to increased contamination of water bodies.
Affected water sources include:
- Recreational waters such as lakes and beaches.
- Shellfish harvesting waters.
- Primary sources of drinking water.
Extreme weather events can exceed the designed capacity or cause physical damage to water infrastructure, including:
- Wastewater treatment plants.
- Drinking water treatment facilities.
Such failures increase the risk that populations will be exposed to significant contaminants.

Waterborne diseases are classified as illnesses caused by microscopic organisms, including viruses and bacteria.
These illnesses are typically contracted through the ingestion of contaminated water or through direct or indirect contact with fecal matter.

Pathogenic Agent: $Salmonella\text{ typhi}$ .
Epidemiology: While rare in industrialized countries, it is widespread in extremely poor regions of developing nations.
Statistical Impact: Estimates suggest that up to $20,000,000$ people are affected each year.
Transmission: The disease is highly contagious and spreads through unsafe water, contaminated food, and poor sanitation.

Context: Commonly found in marginalized villages and during humanitarian emergencies characterized by poverty and poor sanitation.
Symptoms: Causes severe diarrhea and dehydration.
Severity: The infection can be fatal within hours or days of exposure to the bacteria.
Progression: Approximately $1$ in $10$ individuals will develop symptoms that are life-threatening.

Transmission: Shared through contaminated water in ponds, streams, municipal water supplies, and swimming pools.
Pathogenic Agent: A parasite.
Duration: The infection typically resolves after a few weeks, though exposure can lead to lingering symptoms.

Characterization: An intestinal infection presenting with severe diarrhea containing blood or mucus.
Transmission: Spread primarily through poor hygiene and coming into contact with fecal matter.
Cause: Can be triggered by bacteria, viruses, or parasites found in unsafe food and water.
Risk: Mortality risk is high if the individual cannot replace fluids quickly enough.

Biological Role: Various strains exist; some are beneficial for a healthy intestinal tract while others are pathogenic.
Transmission Routes:
- Animal waste contaminating produce on farmland.
- Contamination during the production processes of ground beef.
- Coexistence of cattle and human water sources in unsafe environments globally.

Nature: An infection of the liver.
Transmission: Consuming contaminated food and water or through close physical contact with an infected person.
High-Risk Groups: Individuals traveling in developing countries or working in rural communities with poor sanitation and hygiene management.

Primary Source: Ingestion of food or water contaminated with feces.
Vehicle Foods: Undercooked meat, egg products, fruits, and vegetables.
Vulnerable Populations: Most people recover without complications, but higher risks exist for:
- Children.
- Pregnant women.
- Older adults.
- Individuals with weakened immune systems.

How should students enumerate the different vector-borne diseases with their corresponding pathogen?
What are the implications of vector-borne diseases to mankind?
How should students differentiate between a vector and a vector-borne disease?