One of the most daunting aspects of the novel coronavirus is the way it mutates. The recurrent mutation of SARS-CoV-2 and its route of transmission are still unclear and the scientific community is working relentlessly to find some clarity. According to a recent study in China, the novel coronavirus has mutated into at least 30 different strains and 19 of these strains were previously undiscovered. The study is limited to analysis of strains from 11 randomly chosen COVID-19 patients from Hangzhou and it hints at the unpredictable number of genetic mutations if we consider a global scenario. The route of transmission and the modes of transportation of this multifaceted virus are equally important. Though the primary source of coronavirus is believed to be bats humans are to blame for spreading it. Initially SARS-CoV-2 was diagnosed as a respiratory virus and the transmission occurs via respiratory droplets while contact transmission was identified later on. Yet the transmission via food packaging materials and takeaway from groceries remains on board.

Researchers started looking into sewage and traces of SARS-CoV-2 were found in the Netherlands and Paris wastewater samples. This is the potential mode of transmission that might recur in a completely different way. The wastewater transmission risk was thought to be low beforehand and the extent of this route transportation needs more research. The medical and municipal wastewater can be a potential source of water-based transmission and thus sewage surveillance can be used to get an idea if the virus exists in a community. Also medical waste and wastewater management should be a top priority in the hospitals that are providing healthcare to COVID-19 patients. 

The medical waste management system is quite different than the municipal one. Usually medical waste and wastewater go through special treatment which ensures disinfection before disposal. But in Bangladesh, the scenario of medical waste and wastewater handling is quite frightening and treatment facilities for these wastes and wastewater is rare. After this battle against novel coronavirus, we will be loaded with tons of medical solid waste including the discarded PPEs. Wastewater is regularly generated from medical support premises and mostly released in the municipal sewerage system without any treatment and in worst cases, released into open drains. This is quite concerning as the coronavirus can use this mode of transmission to find its way into the drinking water source. SARS-CoV-2 can survive in human excreta and urine of infected persons that ultimately reaches septic tanks. A matter of relief is that most residential building premises run decentralised faecal sludge management by using septic tanks and soak pits in Bangladesh. But still there are vulnerable communities that are deprived by the standardised sludge management facility and proper hygiene practices. 

We can follow the examples set by China in handling the medical waste and wastewater and start with the initial screening of the medical waste and wastewater treatment scenario of the specialised hospitals for COVID-19 cases and isolation units for suspected possible cases. After the initial screening, we can improve the situation with multiple regulations to deal with this crisis especially limiting the hygiene index that is measured by FC (Faecal Coliform) count to a much lower value than the previous standards. Also, the medical solid waste, sludge can be treated as hazardous waste and the air exhaust from the treatment should also be disinfected. In Wuhan, China applied sodium hypochlorite in municipal sewage treatment plants to disinfect the effluent and sludge. Thus they achieved full disinfection in all 26 treatment plants but residual chlorine was detected in 147 drinking water sources due to super-chlorination. With the lessons learned from China, in Bangladesh, we can use the "Breakpoint Chlorination Curve" to investigate the proper dosage of chlorine-based disinfectants to avoid contamination of drinking water sources. The most important part to prevent water-based transmission in this rainy season should be the blockage of medical wastewater flow into the rainwater. It can be done by decentralising the temporary venues dealing with COVID-19 cases from the central sewerage system. Also close monitoring of wastewater samples from designated medical wastewater outlets and municipal sewerage systems should be conducted where COVID-19 tests is required. The health safety of the sanitation workers in this critical period needs strict supervision and continuous monitoring to prevent them from getting infected. 

It is important to realise that maintaining social distance and personal hygiene will help us to flatten the curve of COVID-19 cases but to prevent another "strike" from a more complex genetic mutation, wastewater surveillance and inactivation of the virus is a must. Having a determined full proof strategy to block transmission routes through waterways may be a life-saving decision.

Farah Rahman Omi is assistant professor, Department of Disaster Engineering and Management, Chittagong University of Engineering and Technology.