11 Sludge Hygienisation—A Novel Technology for Urban Areas …
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still well understood and need continued scientific exploration [54, 55]. The bats are
thought to be the most likely ecological reservoirs for SARS-CoV-2. However, it is
believed that the virus got transmitted to the humans via another intermediate animal
host. While the possibilities include domestic food animals, wild animals, as well
as, domesticated wild animals; the identity of the intermediate animal host has not
been ascertained yet [56].
The human-to-human transmission of pathogens can be effectively traced through
a deeper understanding about the manifestation of a pathogen inside the carrier (host),
the transmission through the fecal–oral route, and the sustenance of the pathogens
in the environment. For example, pathogens responsible for enteric diseases can get
transmitted from one human host to another in two different ways, viz. (a) via the
direct contact (fecal–oral route) and (b) via indirect contact (e.g. through contaminated fluids, such as surface water; food, currency notes and fomites, such as clothes,
utensils and furniture, that are likely to contain infectious particulates because of daily
usage by an infected host (human) [55].
It is to be noted that most of the pathogens that are transmitted via the fecal–
oral route are likely to be very stable and can even sustain under reasonably hostile
conditions. This ability is exhibited by the success passage of live infectious particles
through the varying pH conditions of the gastrointestinal tract that includes acidic
ambience of stomach and alkaline or mildly acidic ambience of the intestine the
hostile conditions [55].
Furthermore, researchers have found that viruses, helminths and the protozoan
cysts and oocysts (a cyst that contains a zygote formed by a parasitic protozoan)
exhibit longer sustenance (ranging from a few days to several months) in the environment as compared to the vegetative bacteria [17, 54]. Therefore, the discovery
of live COVID virus and the SARS-CoV-2 RNA fragments in the human faeces as
mentioned before, elevates the danger of community spread. Further, it is reported
that COVID 19, with its high transmissibility, can result in the spread of the virus to
at least 2–2.5 uninfected individuals from each infected individual on an average, if
the precautionary measures, such as social distancing, are not strictly abided by [57].
The human-to-human transmission of a typical enteric pathogen via the fecal–
oral route is largely dependent on the three distinct phases of transmission amplification, viz. (a) Amplification within the donor (host): The amplification within
the host depends on a few key factors, such as the gut microbiome (the genome
of all the microorganisms, symbiotic and pathogenic, living in the intestine) of the
donor, pathogenicity (ability to cause diarrhea) of the microorganism, niche adaptation of the pathogen within the intestinal tract of the host (persistence) and the
extent of shedding in the faeces; (b) Amplification in the Environment (during
the transmission): The amplification of pathogenicity in the environment primarily
depends on the environmental stability of the particular pathogen, habits and practices of a human community in connection with food and hygiene (agriculture, food
processing, food storage and transport, etc.) and also on the environmental microbiome; (c) Amplification within the receptor: The amplification within the receptor
is akin to that in the donor, and largely depends on the receptor gut microbiome,
271
still well understood and need continued scientific exploration [54, 55]. The bats are
thought to be the most likely ecological reservoirs for SARS-CoV-2. However, it is
believed that the virus got transmitted to the humans via another intermediate animal
host. While the possibilities include domestic food animals, wild animals, as well
as, domesticated wild animals; the identity of the intermediate animal host has not
been ascertained yet [56].
The human-to-human transmission of pathogens can be effectively traced through
a deeper understanding about the manifestation of a pathogen inside the carrier (host),
the transmission through the fecal–oral route, and the sustenance of the pathogens
in the environment. For example, pathogens responsible for enteric diseases can get
transmitted from one human host to another in two different ways, viz. (a) via the
direct contact (fecal–oral route) and (b) via indirect contact (e.g. through contaminated fluids, such as surface water; food, currency notes and fomites, such as clothes,
utensils and furniture, that are likely to contain infectious particulates because of daily
usage by an infected host (human) [55].
It is to be noted that most of the pathogens that are transmitted via the fecal–
oral route are likely to be very stable and can even sustain under reasonably hostile
conditions. This ability is exhibited by the success passage of live infectious particles
through the varying pH conditions of the gastrointestinal tract that includes acidic
ambience of stomach and alkaline or mildly acidic ambience of the intestine the
hostile conditions [55].
Furthermore, researchers have found that viruses, helminths and the protozoan
cysts and oocysts (a cyst that contains a zygote formed by a parasitic protozoan)
exhibit longer sustenance (ranging from a few days to several months) in the environment as compared to the vegetative bacteria [17, 54]. Therefore, the discovery
of live COVID virus and the SARS-CoV-2 RNA fragments in the human faeces as
mentioned before, elevates the danger of community spread. Further, it is reported
that COVID 19, with its high transmissibility, can result in the spread of the virus to
at least 2–2.5 uninfected individuals from each infected individual on an average, if
the precautionary measures, such as social distancing, are not strictly abided by [57].
The human-to-human transmission of a typical enteric pathogen via the fecal–
oral route is largely dependent on the three distinct phases of transmission amplification, viz. (a) Amplification within the donor (host): The amplification within
the host depends on a few key factors, such as the gut microbiome (the genome
of all the microorganisms, symbiotic and pathogenic, living in the intestine) of the
donor, pathogenicity (ability to cause diarrhea) of the microorganism, niche adaptation of the pathogen within the intestinal tract of the host (persistence) and the
extent of shedding in the faeces; (b) Amplification in the Environment (during
the transmission): The amplification of pathogenicity in the environment primarily
depends on the environmental stability of the particular pathogen, habits and practices of a human community in connection with food and hygiene (agriculture, food
processing, food storage and transport, etc.) and also on the environmental microbiome; (c) Amplification within the receptor: The amplification within the receptor
is akin to that in the donor, and largely depends on the receptor gut microbiome,