Environmental
Reservoir
Humans are the primary reservoir for poliovirus. While it is possible for chimpanzees and monkeys have demonstrated the ability to carry the virus, they have not been shown to be a significant reservoir.
Shedding
It has been shown by a study of infected people in a tropical community in a developing country that an individual can shed more than 10^6 virus particles per gram of feces excreted.
Occurrence
Water
Drinking Water
Enterovirus contamination in drinking water is rare if the water is properly treated, though low levels have been detected (Committee on Drinking Water 1979. It is unknown whether these low levels are sourced from viruses that made it through the treatment process or were introduced to the supply after treatment. The later hypothesis is of particular concern to virologists as low doses are capable of causing systemic infection that could go undetected for extended periods of time.
Ground Water
Virus occurence in groundwater is more common among shallow reservoirs and below surfaces that have had sewage or sludge application.
| Organism | Location | Concentration | Reference |
|---|---|---|---|
| Enteroviruses | Groundwater (Israel) | 20% of 99 samples (12% of positive samples were absent of other fecal indicators) | Marzouk, Goyal, and Gerba 1979 |
Surface Water
Enteroviruses can be isolated in low concentrations from almost all surface waters receiving human wastes.
Food
A major risk factor for virus ingestion are fish and shellfish, which an absorb the virus in the environment and eventually release it into humans when consumed. Isolation of enteroviruses from wild oysters living in lightly contaminated waters has been frequently reported.
| Organism | Location | Concentration | Reference |
|---|---|---|---|
| Poliovirus | Oysters in seawater | 600 oysters submerged in 20°C seawater spiked with 10^6 polioviruses / L. Within 1 hour virus concentration in the oysters was 27x higher than in the surrounding water. | Mitchell and others 1966 |
| Poliovirus | Olympia oyster & Manila clam | Contained 10x - 180x higher than in surrounding waters | Hoff and Becker 1969 |
| Poliovirus | Olympia oyster & Manila clam | Contaminated shellfish were held in disinfected seawater (6-16 deg C), concentrations in meat was reduced >99.9% after 96 hours | Hoff and Becker 1969 |
| Poliovirus | Oysters in natural seawater environment | 7.6% of samples contained enteroviruses in environment where 5.6% of water samples were positive. | Vaughn and Metcalf 1975 |
| Poliovirus | Clams (Great South Bay, NY, USA) | 30 viruses / 100 g of clam flesh | Vaughn, et al. 1979 |
Fomites
Sewage
| Organism | Location | Concentration | Reference |
|---|---|---|---|
| Enterovirus | Sewage (Lansing & East Lansing, MI, USA) | 7% and 14% of samples | Bloom, et al. 1957 |
| Enterovirus | Sewage (Haifa, Israel) | 6x10^3 to 4.9x10^5 / L | Buras 1976 |
| Enterovirus | Sewage | 1x10^6 | Buras 1976 |
| Enterovirus | Sewer-stormwater overflows (Seattle, USA) | 1.3x10^3 viruses / L | Heyward et al. 1979 |
| Poliovirus | Sewer-stormwater overflows (Seattle, USA) | 1.3x10^3 viruses / L | Heyward et al. 1979 |
| Enterovirus | Sewage (Ottawa, CA) | Virus detection in 79% of samples, 7% of isolates were poliovirus | Sattar and Westwood 1977 |
| Enterovirus | Raw sewage (Hawaii, USA) | 100% of samples had enterovirus isolates at 1.9x10^4 / L | Fujioka and Loh 1978 |
| Enterovirus | Raw sewage (India) | 11,500 / L (80% of which were had poliovirus) | Rao, Lakhe and Waghmare 1978 |
Enterovirus occurence in sewage can experience wide fluctuations depending on the infection status of the sewage system users. That being said, nearly all sewage systems contain some level of enterovirus. Generally, the level of enterovirus contamination increases when the served community has poor hygiene or large proportion of children. One can assume that sewage in developing countries contains at least 10^5 enteroviruses per liter (Feachem, 1983). Occurrence is greatest during the summer and fall months (July through November).
Air
Airborne droplets of water and wastewater may contain enteroviruses, and these viruses may result in infection when inhaled. These droplets can be produced by flushing the toilet, spray irrigation, recreational activity (boating, splashing, etc.) or bubbling action such as is seen in activated sludge plants. Gerba, Wallis and Melnick (1975) found that when water seeded with 10^8 polioviruses was flushed, at least 2.8x10^3 infectious units up to seat level. It was also shown that it is possible for theses organisms to deposit throughout the bathroom.
Moore, Sagik, and Sorber (1979) were able to isolate small numbers of enteroviruses (up to 1.7x10^-2 per m^3 of air) 50 meters downwind of the wet-line edge of a wastewater spray irrigation site in California, USA.
Persistence
Water
| Organism | Location | Persistence | Temperature | Reference |
|---|---|---|---|---|
| Enteroviruses | Groundwater | 90% reduction @ 11-14 days | Yeager and O'Brien 1977 | |
| Enteroviruses | Shallow ground water (Florida, USA) | 28 days | Wellings et al, 1975 | |
| Poliovirus | River water | 90% inactivation @ 46 hrs | 4-8°C | O'Brien and Newman 1977 |
| Poliovirus 1 | Rio Grande River (New Mexico, USA) | 90% inactivation @ 25 hrs | 23-27°C | O'Brien and Newman 1977 |
| Poliovirus 3 | Rio Grande River (New Mexico, USA) | 90% inactivation @ 19 hrs | 23-27°C | O'Brien and Newman 1977 |
| Poliovirus | Farm pond water | 100% inactivation @ 63-84 days | 20-25°C | Joyce and Weiser 1967 |
| Poliovirus | Farm pond water | Survived for >91 days | 4°C | Joyce and Weiser 1967 |
| Poliovirus 1 | Fresh water (polluted & non-polluted) | 3 log reduction @ 3 to >14 days | 20°C | Hurst and Gerba 1980 |
| Poliovirus | Tap water | 99.9% inactivation @ 91 days | 18-25°C | Lefler and Kott 1975 |
| Poliovirus | Distilled water | 99.9% inactivation @ 112 days | 18-25°C | Lefler and Kott 1975 |
| Poliovirus | Tap water | "completely stable in tap and distilled water for 231 days" | 4-8°C | Lefler and Kott 1975 |
| Poliovirus | Tap water | 99% inactivation @ 80 days | 18-23°C | Kott, Ben-Ari and Vinokur 1978 |
Survival in water is dependent primarily upon temperature and extent of contamination. At temperatures less than 10°C survival times of between 24 and more than 272 days are reported. At temperatures above 20°C the range is 4 to 135 days (Feachum, et al. 1983). These studies were done in drinking water generally considered well treated. Little data exists as to the survival rates in systems that produce variable quality water like those found in many developing nations.
Feces & Sewage
| Organism | Location | Persistence | Temperature | Reference |
|---|---|---|---|---|
| Poliovirus | Sewage | 99.9% @ 42 days | 18-25°C | Lefler and Kott 1975 |
| Poliovirus | Sewage | 99.9% @ 231 days | 4-8°C | Lefler and Kott 1975 |
| Poliovirus | Sewage | 100% "disappearance @ 110 days | 18-23°C | Kott, Ben-Ari and Vinokur 1978 |
| Poliovirus | Bombay sewage | 22-40% loss @ 2 days | 8°C | Rao, et al 1977 |
Results of several studies indicate longer survivals than in river water, with survival times of over 231 days at <10°C and up to 110 days at 20°C (Feachum, et al 1983). It is hypothesized that prolonged survival in sewage is due to adsorption to solids.
Fomites
Food
| Organism | Location | Persistence | Temperature | Reference |
|---|---|---|---|---|
| Poliovirus | Oysters in contaminated seawater | Survival for >6 days | Hedstrom and Lycke 1964 |
Low humidity environments will generally reduce the survival time (Feachum, 1983)
Crops
| Organism | Location | Persistence | Temperature | Reference |
|---|---|---|---|---|
| Enteroviruses | Seeded produce | Undetectable on various produce @ 4-5 days | 4°C | Konowalchuk and Speirs 1975 |
| Enteroviruses | Seeded Produce (dilute feces) | 4-5% detectable @ 5 days | 4°C | Konowalchuk and Speirs 1975 |
| Enteroviruses | Seeded Produce (undilute feces) | 7-12% detectable @ 5 days | 4°C | Konowalchuk and Speirs 1975 |
| Poliovirus | Grape bunches | 99% reduction @ 5 days | 22°C | Konowalchuk & Speirs 1977 |
| Poliovirus | Seeded tomatoes and parsley applied with unchlorinatedwaste stabilization pond effluent w/ exposure to sunlight | 2.2% recovery @ 6 hrs | Kott & Fishelson 1974 | |
| Poliovirus | Seeded tomatoes and parsley applied with chlorinatedwaste stabilization pond effluent w/ exposure to sunlight | 1.6% recovery @ 6 hrs | Kott & Fishelson 1974 | |
| Poliovirus | Seeded tomatoes and parsley applied with unchlorinatedwaste stabilization pond effluent in darkness | 12.7% recovery @ 6 hrs | Kott & Fishelson 1974 | |
| Poliovirus | Seeded tomatoes and parsley applied with chlorinatedwaste stabilization pond effluent in darkness | 8.5% recovery @ 6 hrs | Kott & Fishelson 1974 | |
| Poliovirus | Seeded tomatoes (outdoors) | 100% inactivation @ 24 hrs | 15-31°C | Kott & Fishelson 1974 |
| Poliovirus | Seeded parsley (outdoors) | 100% inactivation @ 48 hrs | 15-31°C | Kott & Fishelson 1974 |
| Poliovirus | Lettuce and radishes sprayed with secondary effluent/sludge 8-10 days after planting (2.5x10^8 viruses/L) | Days immediately following spraying: Recovery of 2.9x10^4 viruses/100 g Two weeks after: Recovery of 100 viruses/100 g >36 days: Recovery of 10 viruses/100 g |
19-34°C (Exposed to the Ohio summer which consisted of sunlight and periodic rain) Soil temperature of 45°C | Larkin, Tierney and Sullivan 1976 |
| Enterovirus | Spiked water droplets on vegetables (lettuce, celery, green peppers, tomatoes, radish, and carrots) | Undetectable @ 4-5 days | 4°C | Konowalchuk and Speirs 1975 |
| Enterovirus | Dilute feces on vegetables (lettuce, celery, green peppers, tomatoes, radish, and carrots) | 4-5% @ 5 days | 4°C | Konowalchuk and Speirs 1975 |
| Enterovirus | Undilute feces on vegetables (lettuce, celery, green peppers, tomatoes, radish, and carrots) | 7-12% @ 5 days | 4°C | Konowalchuk and Speirs 1975 |