On February 19, 2020, WEF published The Water Professional’s Guide to COVID-19. The Guide was meant to increase water sector awareness of COVID-19 virus and any water and wastewater-related issues and relevant resources. The content was reprinted in the April 2020 issue of Water Environment & Technology. Since then, the World Health Organization (WHO) has declared COVID-19 a pandemic and the disease has spread to more than 210 countries with more research on the virus being published every day. In an effort to keep the water community informed of COVID-19 developments, the Waterborne Infectious Disease Outbreak Control (WIDOC) working group has prepared an update to highlight the latest scientific findings, as well as topics not previously addressed. The goal is to contextualize these new results and state the implications and significance from a water and wastewater collection and treatment, public health and water resource recovery facility (WRRF) worker perspective. Primary Messages The research community has yet to find evidence of survival of infective COVID-19 virus in feces and in wastewater systems. Efforts are ongoing to assess the relative risk of exposure to wastewater. Current efforts estimate numbers of infections in the community and support public health surveillance by detecting the virus in wastewater using molecular techniques that identify presence and quantities of genetic material (RNA). This method does not assess virus viability or infectivity.
Future research on COVID-19 virus is encouraged to investigate concentrations of infective virus in feces (if any), shedding patterns in patients and factors influencing persistence of infective virus in plumbing and collection systems. Research is ongoing, but experts currently believe that exposure to wastewater is not a significant transmission route for COVID-19 virus. WEF continues to work on improving protection of wastewater workers from pathogen exposure — especially via aerosols — by forming a Blue Ribbon Panel to address the issue of required personal protective equipment, as well as protective work and hygiene practices. Coronavirus and Water Systems WSEC-2020-TR-002 Water Environment Federation Page 2 | 27 This update reinforces our previous recommendations, which align with the U.S. Centers for Disease Control and Prevention (CDC), the U.S. Occupational Safety and Health Administration (OSHA), WHO and the Pan American Health Organization (PAHO). There is still no evidence that coronavirus survives the disinfection processes utilized for drinking water and wastewater treatment. No coronavirus-specific protections are recommended for workers working in wastewater treatment and collection systems. However, as data emerges almost daily with regard to this virus, heightened vigilance in compliance with existing personal protective procedures is appropriate to control exposure.
Does detecting COVID-19 virus RNA mean the virus is infective?
No. As explained below, viruses can be detected using a variety of methods. Some test whether the virus can infect cells, while others just look for nucleic acids (also called RNA or RNA fragments). But viruses need much more than just their RNA to successfully infect cells, so detecting RNA is a little bit like detecting an antibody — it tells you that the virus was once there, but not whether it is still there and is infectious now. Virus structure and function Not all pathogenic viruses detected in the built environment by molecular methods are infectious (Prussin et al. 2020). To understand the difference between detecting RNA and detecting infective virus, we must first understand the basic structure and biology of viruses. When outside a host, viruses are considered non-living or inert particles called virions. Virions are not cells. They are made up of nucleic acids — DNA or RNA — contained in a protein coat (called a capsid) and in some cases, such as COVID-19 virus, they are surrounded by a lipid envelope. Most importantly, they do not have the necessary parts to replicate (i.e. produce copies of themselves) on their own, so they need to find a host cell, hijack it, and make it produce copies of the virus. Figure 1 depicts COVID-19 virus attaching to a receptor on a host cell.
In this process, the red spikes on the surface of the COVID-19 virus (called the S proteins) are extremely important. These S proteins allow the virus to attach to the host cell receptors (ACE2) and gain entry into the host cell to replicate. This means that, in principle, all cells carrying ACE2 receptors in the respiratory or intestinal tract can potentially be hijacked by COVID-19 virus.
Can COVID-19 virus spread through the sewerage system?
Summary: Despite prolonged shedding of the virus RNA in feces, experts believe that exposure to wastewater is not a significant transmission route for COVID-19. However, most scientific efforts related to wastewater thus far have not looked for infective viruses. Instead they have focused on quantifying virus RNA levels to try to estimate the infection rate in the population, thereby aiding public health surveillance and infection control in the population. It is important to note that detection of virus RNA by RT-PCR provides no indication that the virus is infectious. Implications for water professionals: While much is still unknown about COVID-19 virus shedding and transmission, CDC and WHO state that current evidence does not support that COVID-19 virus is transmitted via wastewater.
Water professionals should be able to communicate that the detection of COVID-19 virus RNA in wastewater does not translate to public health risk and does not result in the need for change in operations or procedures by utilities. The preliminary data from treated effluent suggests that wastewater treatment processes that are in place already are sufficient for COVID-19 virus control. This data corresponds with CDC, OSHA, WHO, and WEF recommendations. The data produced from surveillance of RNA could indicate the scale of the outbreak and aid in emergency response planning in communities and at utilities (i.e., prediction of absenteeism and critical staff management), but these data need to be interpreted with caution
Can COVID-19 virus spread through the fecal-oral contamination route?
Summary: There is currently no evidence of fecal-oral transmission of COVID-19; however, scientific evidence supports the possibility of this transmission route for the following reasons:
• COVID-19 virus was found to bind to receptors in the lungs and intestinal tract; its ability to infect and reproduce in the intestinal tract suggests that it can be excreted with feces in a potentially infective state.
• COVID-19 RNA has been recovered from a large percentage of COVID-positive patients’ fecal material and anal swabs. It also has been recovered from toilet bowls and sinks from positive patients’ rooms.
• Virus RNA was recovered from untreated wastewater in three studies but was not detected in treated wastewater in the one study where it was analyzed.
• Infective virus was detected in feces in two studies without quantification. However, other reports have documented the inability to detect infective virus in stool samples from positive patients.
• Infective virus shows multiple shedding routes, including saliva and respiratory secretions.
• Virus can be highly stable under some conditions, e.g., at room temperatures in laboratory conditions. Implications for water professionals: Due to the multiple shedding routes of the virus from infected individuals, COVID-19 virus, or at least its RNA, may reach collections systems and WRRFs in wastewater. The virus has the potential to be present in sanitary sewer overflows (SSOs) and combined sewer overflows (CSOs). While much about COVID-19 virus transmission remains unknown, experts currently believe that exposure to wastewater is not a significant transmission route for COVID-19 virus. The evidence from the Netherlands, however, preliminarily supports the recommendations made by WHO, CDC, OSHA, and WEF and confirms that wastewater treatment can be effective at managing viral risk.
Comparing SARS, MERS and COVID-19 viruses Summary:
COVID-19 virus has been shown to be more transmissible than SARS-CoV and MERSCoV. Like SARS-CoV, it uses ACE2 receptors on host cells in the respiratory and gastrointestinal systems to invade host cells and can survive in aerosols and fomites for hours. Implications for water professionals: Despite differences in resulting illness, data extrapolated from SARS-CoV and MERS-CoV (as well as other surrogates) have been helpful in predicting COVID-19 virus behaviour and recommending appropriate risk management practices before analyses specific to COVID-19 virus is completed and validated. Details: Compared with the known SARS-CoV and MERS-CoV genome, COVID-19 virus is closer to the SARS-like bat CoVs in terms of the whole genome sequence. Most genomic encoded proteins of COVID-19 virus are similar to SARS-CoV, though certain differences do exist. Several independent research groups have identified that COVID-19 virus belongs to β-coronavirus group, with high genomic similarity to bat coronavirus. Though this points to bats as the natural host, the identity of an intermediate host is still not confirmed. Current reports still show that COVID-19 virus may be more transmissible, while causing less serious illness or virulence compared to SARS-CoV and MERS-CoV (Guo et al., 2020). As of March 1, 2020, the currently analyzed mortality of COVID-19 is 3.4%, lower than death rate of SARS (9.6%) and MERS (around 35%), respectively (de Wit et al., 2016). Binding to the host cells is a critical step for viral cell entry and infection. Studies have shown that the COVID-19 virus binds to host cells through its spike glycoprotein and uses the same host cell receptors — angiotensin-converting enzyme 2 (ACE2) – as that for SARS-CoV tract (Hoffman et al., 2020; Wan et al., 2020). ACE2 protein is present in abundance on lung alveolar epithelial cells and the enterocytes of small intestine, which may explain the routes of infection and disease manifestations (Guo et al., 2020). A study by Wrapp et al. (2020), compared the biophysical strength of binding between the glycoprotein spikes of the COVID-19 virus and the SARS-CoV and found this protein binds at least ten times more tightly than the corresponding spike protein of SARS–CoV to their common host cell receptor. The authors proposed that this may explain the higher transmission rate of COVID-19 from human to human; however, additional studies are needed to investigate this possibility. MERS-CoV, on the other hand, uses dipeptidyl peptidase 4 (also known as CD26). Comparisons of aerosol and fomite survival of SARS-CoV and COVID-19 virus have shown that the viruses have very similar half-lives and that differences in disease transmission stem from other infection characteristics
Reference & Source Information: https://www.wef.org/
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