Environmental Surveillance of Infectious Diseases

These flashcards cover key concepts related to environmental surveillance, wastewater monitoring, and One Health approaches to infectious diseases.

What are environmental reservoirs for infectious diseases?

Environmental reservoirs are locations where potential human and domesticated animal pathogens can be found, such as water or soil.

What is the role of environmental surveillance in infectious disease monitoring?

Environmental surveillance monitors potential or known pathogens from environmental samples to detect emerging diseases before they enter human or animal populations.

What percentage of emerging pathogens are zoonotic?

Approximately 75% of emerging pathogens are zoonotic.

What is a One Health approach?

One Health is a collaborative approach that integrates multiple sectors, such as animal and human health, to improve public health outcomes.

what is the most common PCR method used and how?

RT-qPCR is a common method used for the amplification and detection of SARS-CoV-2 RNA in wastewater.

this targets the genes:

• RNA-dependent RNA polymerase (RdRp)

• envelope (E)

• nucleocaspid (N)

• spike (S) sometimes

  • can reduce sensitivity

What are some advantages of wastewater surveillance?

Wastewater surveillance allows for monitoring of viral spread across an entire region and can detect viruses even when clinical testing coverage is low.

what are the challenges with wastewater surveillance?

• quantification

  • differences in excretion rates of viruses during course of infection

  • variation in wastewater infrastructure and environment

  • population fluctuation due to travel

    • ex: spring break, migration, etc

• degradation of viral particles and genetic material not well characterized in environment

• ethical issues associated with population level surveillance

What is human fecal normalization?

It is the process of normalizing SARS-CoV-2 concentrations in wastewater to account for changes in human waste input over time.

What ethical considerations are associated with wastewater surveillance?

• good

  • underserved and vulnerable populations can be prioritized to avoid outbreak

  • cost effective and almost anonymous

• bad

  • vulnerable marginalized population can be targetted for extra surveillance leading to more stigmatization

  • marginalized populations might not be serviced by the sewage network

Why is laboratory control essential in wastewater surveillance?

Laboratory controls are necessary for comparing SARS-CoV-2 RNA concentrations over time and ensuring accurate results across different testing methods.

What does the term 'spillover events' refer to in infectious disease contexts?

Spillover events are instances when pathogens from environmental reservoirs enter and circulate within human or domesticated animal populations.

How can wastewater surveillance function as an early warning system?

It can identify the presence of SARS-CoV-2 RNA in wastewater prior to clinical confirmation of cases, allowing for proactive health measures.

What are the implications of using wastewater surveillance for monitoring SARS-CoV-2 variants?

Variants can be identified and monitored through lineage-specific PCR and sequencing to understand population changes over time.

What is the estimated sensitivity of wastewater surveillance for SARS-CoV-2?

The estimated sensitivity of wastewater surveillance can be up to 80% at a clinical incidence of 13 cases per 100,000 people.

What was the conclusion regarding wastewater surveillance of pathogens?

Wastewater surveillance provides qualitative assessments and can track trends in disease spread over time, requiring ongoing validation of methods.

what are some examples of pathogens with environmental reservoirs?

• vibrio cholera = brackish water

• legionella pneumophila = fresh water, plumbing

• clostridium tetani = soil

• clostridium botulinum = soil, food contamination

• listeria monocytogenes = soft cheese/raw milk, soil, water

• hepatitus A virus = water, food

• norovirus = water, environmental surfaces

• giardia lamblia = water

how are pathogens shed by humans into the environment?

human waste, scats, snot, etc

how did they apply wastewater surveillance in yellowknife?

in yellowknife they had positive wastewater tests which led to the testing of travellers to identify asymptomatic travellers who were shedding the virus at the end of their self-isolation period

how does population-wide surveillance work by applying wastewater surveillance?

looking at many different treatment plants alongside reduced clinical testing to estimate the prevalence of covid

how does specific population surveillance work by applying wastewater surveillance?

testing wastewater directly at a facility’s septic system for covid

can have strong ethical and social implications

how to detect variants and mutations of interest or concern in wastewater?

• lineage specific PCR

  • PCR primers need to be updated as the virus mutates

• sequencing

  • needs to be processed with bioinformatic tools

what did wastewater surveillance sensitivity conclude about covid?

fecal → oral route is not likely a major concern of SARS-CoV-2 transmission

what are the advantages of wastewater surveillance?

• allows identification of viruses for an entire geographical region connected by water treatment systems

• enables monitoring of viruses even if they do not result in symptomatic diseases or if clinical diagnostic test coverage is low/biased

• can provide population level, sensitive, and low biased method to monitor the spread of SARS-CoV-2

  • if coupled with seasoning, could identify different variants to understand viral population changes over time

what are some method for detecting SARS-CoV-2 in untreated wastewater?

• ultrafiltration

• electropositive membrane (viruses are negatively charged)

• PEG precipitation

• flocculation (chemical coagulant)

• ultracentrifugation

what are the laboratory controls?

• matrix recovery control

  • spike in known amount of non-target nucleic acid

• human fecal normalization

  • target compound specific in human feces

• inhibition assessment

  • use matrix recovery control

• quantitative positive controls

  • run in parallel of the samples tested

• negative controls

  • samples known to have NO SARS-CoV-2

describe matrix recovery control

uses fixed amount of known target is inserted into sample and tracked over the sample preparation process to understand the amount of target lost during the process

>1% of spiked amount can be detected

describe human fecal normalization

normalizes SARS-CoV-2 concentration by the amount of human feces in wastewater

the controls are organisms or compounds specific to human feces to estimate the fecal content

• ex viral targets: pepper mild mottle virus, crAssphage

• ex bacterial targets: bacteroides HF183, lachnospiraceae lachno3

describe inhibition assessment

• when covid concentrations are high, check if the concentrations in the RNA dilute to different levels than expected

  • this is the preferred method since you can evaluate in the same reaction used to quantify covid

• when covid concentrations are low, do the spike thing and compare the concentration to either viral RNA spiked into negatives or to a dilution of the spiked extract