Fate and Transport of Pathogens in the Environment Charles P. Gerba Department of Soil, Water and Environmental Science The University of Arizona Tucson, Arizona

How Important is the Environment in Disease Transmission? 80% of all infections are acquired through the environment Most other infections are acquired from insect bites and direct personal contact (e.g. sex, hand shaking, kissing)

Import Things to Remember about Microbial Transport and Fate Microbes are colloids – not solutes –Log-normal or Possion distributions Microbial transport is influenced by electrostatic and hydrophobic interactions Microbes are individuals

Routes of Exposure Ingestion –Water –Food –Hand to mouth (fomites) Inhalation (aerosols) Dermal

Factors Important in Assessing Exposure Route of Exposure Duration of exposure –Seconds, hours, minutes Number of exposures –How many times in a day, month, year Degree of exposure –Liters of water ingested –Liters of air inhaled –Grams of food ingested

Percentage of Estimated Foodborne Illness Attributable by Agent* Protozoan 3% Bacteria 30% Viral 67% *Mead et al., 1999

Sources of Foodborne Organisms Infected animal Cross contamination –Cutting board to produce (vegetables) Irrigation water Handling and processing –Hand to produce –Wash water –Ice

Accumulation in sediments (viruses occur in higher concentrations in sediment than the overlaying water) Uptake by crustacea and bottom feeding fish Sewage outfall Resuspension by rain, wave action, tides, dredging, etc. Aerosolization by breaking waves Virus association with suspended solids (acts to prolong virus survival) Transport and fate of enteric viruses in the marine environment

FACTS 42 million people in the United States depend on private wells for their source of drinking water There are 100,000 small water treatment systems in the U.S. (< 10,000 persons) 60 million persons depend upon septic tanks for treatment of household wastes

Air/Water Interface Viruses

Life in the 21 st Century Most of our time is spend indoors More people work in offices than ever before We travel more than ever before We spend less time cleaning than the last generation We are less clean (e.g. laundry practices) We spend more time in public places We are more mobile and have more electronic equipment (e.g. cell phones)

Most Diseases Spread Through Hand Contact Every three minutes, a child brings his/ her hand to nose or mouth Every 60 seconds, a working adult touches as many as 30 objects

Occurrence of fecal bacteria on the hand (United States) Preparing a meal Greatest Children after playing Doing the laundry Least Person exiting a toilet

Disease Spread by Fomites Route of exposure –Children under 12 months to their face 60 times per hour –Cross contamination of foods Which fomites are important –How often does hand contact occur on which fomites? Frequency of pathogens on fomites in a given environment Concentration of pathogen on a fomite

Transmission by Fomites Hard surfaces –Phones, tap handles, desk tops, door knobs, cutting boards, table tops Cleaning clothes –Sponges, dish clothes Clothing –Laundry, towels, bed sheets

Transmission by Fomites Bathroom (Bano) –Sinks, taps, bottom of the toilet seat –Norovirus, Graidia, Cryptosporidium, Shigella Kitchen –Sponge, sink, cutting board –Salmonella, Campylobacter Schools –Norovirus, rhinovirus, Salmonella

Sites by Coliform Densities Bath Sink Kitchen Floor Bath Counter Bath Floor Toilet Seat Kitchen Sink Sponge Cutting Board

Classrooms (Grades 4-6) Areas most contaminated with bacteria –Pencil sharpener –Student desk top –Computer –Sink in classroom Viruses isolated –Influenza –Norovirus –Parainfluenza

% Time Coliform Bacteria Detected (public restrooms) Top of the toilet seat20 Flush handle 6 Wall behind toilet 9 Floor in front of toilet64 Sink61 Tap15

% Time Coliform Bacteria Detected (public restrooms) Urinal – inside30 Urinal flush handle 0 Sanitary napkin disposal –outside57 Door knob 4

MRSA Occurrence not Related to Total Bacterial Numbers in Cars

Staph. aureus in Autos

The Forgotten Fomites – Critical Control Points? Phone (cell phone) TV remote Computer keyboard Computer mouse Sink taps/handles Sponges/cleaning clothes Laundry

Bio aerosols

Types of Bioaerosols Sneezing Showers Cooling towers Waste handling –Sewage treatment –Land application of biosolids and sewage –Compost facilities

Factors Affecting the Survival of Microorganisms in Aerosols Relative humidity ( Depends upon the microorganism – optimal may be at either high, low, or medium relative humidity) Sunlight (UV light) Longer survival at night Suspending media (lower survival in the presence of organic matter Temperature – greater survival at lower temperatures

Summary Temperature and sunlight (UV light) are the major factors determining the survival of enteric pathogens in the environment Viruses can travel long distances in groundwater Shellfish concentrate enteric bacteria and viruses from water Enteric pathogens survive less in seawater than freshwater