Water, Water Everywhere, but Is It Safe to Drink?
“Water is life, and clean water means health.” - Audrey Hepburn, Actor, Humanitarian, UNICEF Ambassador
“Thousands have lived without love, not one without water.” - W. H. Auden
Monday was World Water Day. This year the event focused on the theme of valuing water and raising awareness of the global water crisis. We all know that our survival as a species depends on accessibility to fresh, clean water. But globally, more than 2 billion people lack safely managed water, and polluted water is one of the leading causes of death and disease. An astronomical number of microbes also depend on water for their existence. A single drop of either fresh or seawater contains about 1 million bacterial cells and 10 million viruses. A vast majority of these germs are harmless. Nonetheless, some of these microbes cause an estimated 5 million water-related deaths annually. In this Germ Gems post, I discuss several of the microbes that cause major problems for humans and their relation to COVID-19.
Waterborne diseases. Infections that are transmitted through contact with or consumption of microbially polluted water are termed “waterborne diseases.” Waterborne microbes include a long list of viruses, bacteria, protozoa, and parasites. These pathogens characteristically give rise to infections of the gastrointestinal tract, lungs, skin, or brain. The symptoms of waterborne illnesses usually track with the organs involved, such as diarrhea and vomiting in the case of gut infections and cough and shortness of breath for lung infection (pneumonia).
When dealing with waterborne diseases, the phrase “geography is destiny” is especially pertinent. In the developed world, many waterborne diseases are related to recreational activities, such as swimming (e.g., cryptosporidiosis and leptospirosis) and soaking in a hot tub (e.g., Psuedomonas dermatitis and Mycobacterium avium complex, the cause of “hot tub lung”). In contrast, in the developing world, waterborne diseases are inextricably linked to poverty and inadequate hygiene (e.g., typhoid fever and cholera). In 2019, the World Health Organization reported that 1 in 3 people globally do not have access to safe drinking water, and more than half of the world doesn’t have access to safe sanitation services.
Waterborne viral infections. The norovirus is the single most common cause of gastroenteritis (diarrhea) in the developed world (almost 700 million cases per year). Contaminated food, water, and unclean hands transmit the norovirus from person to person. But as was discussed in the March 10 Germ Gems post, “Unintended Positive Consequences of COVID-19,” a marked reduction in the incidence of norovirus gastroenteritis occurred this past year. This precipitous decline in cases was attributed to more assiduous attention to proper hand washing to stop the spread of SARS-CoV-2, the coronavirus that causes COVID-19. (Contrary to media reports, in 2016 the Center for Disease Prevention and Control called the norovirus a “relatively infrequent” visitor to cruise ships and noted that cruise ships accounted for only .01% of all norovirus cases in the U.S.) And although the data are not yet in for other pathogens that cause gastroenteritis, it seems likely that we’ll also see a fall in the number of these cases not only because of global lockdowns and social distancing but also because of an increase in proper hand washing.
Hepatitis A, hepatitis E, adenovirus, rotavirus, astrovirus, and some enteroviruses are a few of the other viruses that can be transmitted by drinking contaminated water. But the virus that is on everyone’s mind is SARS-CoV-2. What about it?
The question of whether SARS-CoV-2 can be transmitted by contaminated drinking water has been on the minds of researchers since the early days of the COVID-19 pandemic. At the outset of the pandemic, attention focused mainly on SARS-CoV-2 as a respiratory tract pathogen. It became recognized very quickly, however, that this coronavirus has a proclivity for infecting many organs that contain cells expressing ACE2 receptors, the docking site on cells for the spike protein of SARS-CoV-2. A June 2020 JAMA Network Open article reported that 12% of patients with SARS-CoV-2 infection had gastrointestinal symptoms, including diarrhea, nausea, and vomiting. Also, shedding of SARS-CoV-2 RNA in stool was detected in 41% of patients. Subsequent studies identified robust expression of ACE2 receptors throughout the gastrointestinal tract. And several research groups found that gastrointestinal manifestations of COVID-19 are a harbinger of severe disease and worse outcomes.
Just because SARS-CoV-2 is found in stools does not mean that water contaminated by such poop can transmit the virus. According to the website of the Center for Disease Prevention and Control (CDC), transmission of SARS-CoV-2 has not been detected in people in the U.S. through the water in lakes, oceans, rivers, or other natural bodies of water. The virus has also not been found in drinking water that was treated to disinfect it from other causes of disease. Scientists in Ecuador, however, found SARS-CoV-2 present in rivers that are sources of drinking water for the inhabitants of its capitol Quito. This finding has raised concerns that water could be a major transmission risk in developing countries that lack adequate sanitation facilities.
In the United States, we take for granted our access to clean water. As Susan Murcott, MIT environmental engineer stated: “I’ve spent 30 years trying to wake people up to the reality of the importance of safe drinking water…I feel like it’s still an invisible problem—invisible, at least, to those of us who are privileged enough to take safe water, sanitation and hygiene for granted.”
We in the United States are privileged. Nonetheless, there have been well-known instances of water contamination here. I vividly remember the largest outbreak of waterborne infection in U.S. history, which occurred in 1993 in our neighboring state of Wisconsin. Over 400,000 Milwaukee residents were sickened by drinking water from Lake Michigan that was contaminated by sewage. The culprit was the protozoan Cryptosporidium parvum.
It is therefore completely understandable that researchers are concerned about the detection of SARS-CoV-2 in wastewater or sewage (used water from sinks, showers, bathtubs, toilets, washing machines, etc.) in both developed and developing countries. In fact, researchers in the field of water engineering have developed guidelines for handling wastewater, which were discussed in Nature Sustainability in December, 2020, “Rethinking wastewater risks and monitoring in light of the COVID-19 pandemic.” In this article, they underscore the need for “a risk assessment and management framework tailored to SARS-CoV-2 transmission via wastewater, including new tools for environmental surveillance, ensuring adequate disinfection as a component of overall COVID-19 pandemic containment.”
Waterborne bacterial infections. In addition to waterborne viral infections discussed above, a large number of bacterial pathogens can also contaminate water thereby precipitating a massive amount of suffering and death worldwide. Legionnaire’s disease (legionellosis) is one; it is a bacterial infection that afflicts and kills more people in the United States than any other reportable waterborne disease, yet it may not even be on your radar screen. Unlike most other waterborne pathogens, Legionella is not acquired by drinking contaminated water. Instead the bacterium is inhaled in aerosols that upon reaching the lungs cause pneumonia.
Most of our knowledge of this infection started in 1976 following an outbreak of pneumonia that occurred among a group of World War II Legionnaires attending a conference in Philadelphia. This led to the discovery of the bacterium Legionella that is now recognized as one of the most common causes of community acquired pneumonia in the developed world, responsible for 8,000-18,000 hospitalizations per year in the United States, with a mortality of about 10%.
The bacterium that causes most cases, Legionella pnuemophila, loves fresh water. It thrives inside protozoa, such as free-living amoebae associated with microbial biofilms that coat wet surfaces, including pipes of drinking water distribution systems, building plumbing systems, faucets, showerheads, cooling towers, hot tubs, and fountains. And these biofilms are extraordinarily difficult to remove.
An article “Legionnaires’ disease in the time of COVID-19” published in the January 2021 journal Open Access cautioned clinicians and those responsible for water delivery in buildings to remember that legionella as well as COVID-19 can be the cause of pneumonia. COVID-19 and Legionnaires’ disease both present with pneumonia and can be clinically indistinguishable. It is therefore important to keep L. pneumophila in mind when evaluating patients admitted to hospital with pneumonia.
In addition, L. pneumophila is known to thrive in biofilms in the pipes of many buildings. (The crisis with the potable water supply of Flint, Michigan was mainly due to lead contamination. In 2014-15 academic researchers, however, also found L pneumonphilia DNA markers detectible in Flint hospital plumbing but not in Flint homes or small buildings.) Hence, the CDC warns that when office and retail buildings come out of lockdown, the buildup of biofilms in pipes could lead to a burst of cases of Legionnaires’ disease. At a March 2021 conference intended for industry, “Prevention of Disease and Injury from Waterborne Pathogens During an Emergent Health Crisis,” CDC experts presented guidelines for reopening buildings safely. These precautions should not be taken lightly.
Bacterial gastrointestinal tract infections (diarrhea) are also very common. On average, an adult in the United States will have two to three bouts of diarrhea (defined as three or more loose stools per day for 3 days) per year, and often the cause is unknown. But when the diarrhea is more severe or prolonged, it is often due to a bacterial pathogen, such as, Shigella, Salmonella, Campylobacter, or Escherichia coli 0157:H7.
Diarrhea in the developing world is a much graver issue. There it kills 2,195 children every day—more than AIDS, malaria, and measles combined. Of the many bacterial pathogens responsible, Vibrio cholera, the cause of cholera, is historically the most notorious. This infection kills 21,000 to 143,000 people worldwide per year. (See the December 3, 2019 Germ Gems post, “Cholera: When Water Turns Deadly.”) Yet the solution to this devastating pandemic is superficially so simple—just provide safe drinking water.
Waterborne protozoa infections. In addition to the waterborne protozoan pathogen Cryptosporidium parvum that causes many cases of diarrhea in both the developed and developing world, two other freshwater protozoans are notorious causes of gastrointestinal tract infections: Giardia lamblia (1 million cases of giardiasis occur in the U.S. annually) and Entamoeba histolytica (amoebiasis affects 50 million people and kills 100,000 globally each year—primarily in the developing world). While vaccines against these pathogens don’t exist, prevention again looks deceptively simple—just provide safe drinking water.
Future challenges and solutions to providing safe water. In 2010, the United Nations General Assembly declared that access to clean water and sanitation is a basic human right. Although we have a long way to go to achieve this right, the lack of accessible water has sparked a desire for scientists and benefactors worldwide to come up with various and creative ways of creating clean water for the world. In an article published in The Science Times in February, 2020, “Seven New Technologies That Create Clean Water for a Thirsty World,” innovative technologies are discussed that could help achieve this hugely important goal. The two that caught my interest were:
· The Fog Harvester—a system of huge mesh fences set up in the Moroccan desert in order to trap fog and turn it into safe-to-drink water and that can produce up to 17 gallons of safe drinking water per single square yard of mesh fence; and
· Life Straw—a straw that can purify up to 1,000 liters and removes 99.9% of parasites and bacteria and claims “to have revolutionized how people in less developed areas of the world drink clean water.”
In addition, while I was writing this Germ Gems post, planetary geologists announced, with unbridled excitement, that “Perseverance,” the NASA robot searching for life on Mars, had detected what looked like an ocean’s worth of water lurking below Mars’ surface crust. Upon hearing this announcement, my first thought was wouldn’t it be better if the amount of money invested in the exploration of the Red Planet were spent on technologies to bring safe drinking water to those in desperate need on our planet? Then I quickly remembered that many extraordinary breakthroughs were spawned by scientific and technological achievements that didn’t appear at first to have any immediate, practical payoff. Admittedly, it would be out of this world if all that went into this discovery on Mars led some day to providing everyone on planet Earth with clean water!