February 18, 2020 in COVID-19 virus

The 2019-nCoV coronavirus: Are there two routes to infection?

The new virus may be expelled from a human via respiratory and intestinal means.

SHARE: Share on PRINT ARTICLE:print this page https://doi.org/10.1287/orms.2020.02.01

The new 2019-nCoV virus started spreading in December 2019 in Wuhan, China. Source: Pixabay

What does it mean, “to be in contact with someone”?

In Wuhan, China, in December 2019, a 34-year-old doctor, Li Wenliang, noticed a strange new virus. “I knew it (was contagious) when the patient I came in contact with infected her family, and I was infected right afterward,” Dr. Li said. “Thus, I discovered it was highly contagious. The patient had no symptoms, so I got careless” [1].

Dr. Li thought the illness resembled SARS, which originated in the Guangdong province of southern China in 2002 and was identified in 2003. As he reported, “It was (thought) that SARS might come back. We needed to be ready for it mentally. Take protective measures.” Dr. Li tried to warn his colleagues and disseminate news of the new virus. For that he was punished by authorities and forced to recant. That led to weeks of delay before authorities seriously dealt with the new virus. Now a national hero, Dr. Li died on Feb. 7 from the virus he acquired from his first patient.

The vast majority of accounts of the new 2019-nCoV virus refer to it as a respiratory infection. But since the 2003 SARS epidemic was cited by Dr. Li, we may ask, “What was the major vehicle for transmission of SARS, person to person?” That takes us to Amoy Gardens of Hong Kong, a residential complex with 19 buildings and the site of the largest community outbreak of SARS. More than 300 cases of SARS occurred there, the largest fraction attributed to one super spreader. The individual – a 33-year-old Shenzhen resident in Hong Kong for kidney treatment was infected with SARS but had severe diarrhea as a key symptom. Those living in the same building in Amoy Gardens vertically either above or below the infected individual became ill very quickly, nearly all at the same time. The infected person never met face-to-face with the vast majority of those he infected.

Detective work traced the transmission to broken plumbing in the building, the breaks allowing virus-laden diarrheic gases from the infected man to move into their apartments. Later work found that these infectious, bathroom-generated plumes traveled to other buildings in Amoy Gardens and infected people there, too. Simulation research has shown that such virus-laden plumes can travel up to 200 meters, infecting people [2]. These are astonishing results: While a sneeze or a cough by someone infected with a “respiratory disease” can only infect others within a few meters, the virus-laden gaseous plume from an infected person having diarrhea can infect others up to 200 meters. Some experts estimate that 10%-20% of SARS patients had diarrhea, with the possibility that the virus in their intestinal tracts could potentially infect others by this route [3]. 

Similarities to SARS

Now back to the 2019-nCoV virus, recently renamed COVID-19. From Dr. Li onward, medical professionals in China have remarked how patients seemingly with “no symptoms” were infecting others. But, as Dr. Li suspected, the new virus does share some similarities with SARS. The virus was first found in the fecal matter of an infected individual in the state of Washington (hospitalized on Jan. 19), the first U.S. case of the virus [4]. Shortly thereafter, similar findings of virus-containing fecal matter were reported from Wuhan and Shenzhen [5]. As a result of these findings, physicians and researchers are alerting others to the risk of fecal virus contamination, but usually only with respect to proper hygiene and disposal of fecal matter. Recent published research reports that roughly 10% of patients eventually diagnosed with COVID-19 virus initially showed only diarrhea and perhaps vomiting for one to two days prior to presenting any respiratory symptoms [6]. Similar to SARS [7], the COVID-19 virus has been found in the intestines of diagnosed patients [8].

As far as this author can ascertain (as of Feb. 14, our submission date), the virus-laden gaseous plumes of Amoy Gardens of Hong Kong have not yet been viewed as problematic (with a breaking news exception, as noted below). One does not even have be at a toilet to expel intestinal gas (flatulence), and the typical adult will do this 12 to 25 times a day, producing 0.6 to 1.8 liters of gas [9]. The airborne fecal route may also explain some family-wide infections of the virus, all using the same bathroom, all breathing the same air [10]. Perhaps the infections started with one family member with no visible (respiratory) symptoms. These alternative spreading ideas are not in any way “scientific findings,” only issues worthy of further research. Only research will determine how infectious each type of gas can be.

On Feb. 11, The New York Times reported from Hong Kong – the city with the Amoy Gardens 2003 SARS high-rise super spreader – that a 62-year-old woman living 10 floors below the apartment of a COVID-19-virus-infected person became infected, apparently from “unsealed” sewage pipes [11]. Of the 49 confirmed cases in Hong Kong, three are extended family members of this 62-year-old woman, two living with her in the same apartment. As a precaution, about 50 residents of the building were placed under quarantine. 

Quarantined Cruise Ships

Consider the three quarantined large cruise ships in Asia waters in February 2020: “The Diamond Princess,” anchored off the coast of Yokohama, Japan, with over 3,500 passengers and crew on board; “The World Dream,” docked in Hong Kong with more than 3,600 people on board; and “The Westerdam,” just docked in Cambodia as we write this. Some have labeled these ships as “floating prisons” [12]. The Diamond Princess has had the most cases of the COVID-19 virus, with at least 218 on board becoming infected as of Feb. 13, with maximum daily growth doubling with 70 new infections in one day (Feb. 10). These infections occurred in the presence of attempted on-board self-isolation of the passengers and crew. According to ship Capt. Stefano Ravera, it may be that the doubling of infections in one day was due to infections acquired on land, before the ship was quarantined [13]. If so, once the incubation period for on-land infections is over, we would expect to see a sharp drop in new infections, assuming the self-isolation plan is working.

But what may cause the self-isolation plan not to work? One possible suspect: the fecal matter route of infection. Has this route of infection been seriously examined for these passengers and crew? While most passengers will have private bathrooms in their rooms and suites, they are all connected by a complex, high-tech plumbing system. Some passengers may attempt to flush objects down the toilet that do not belong there, perhaps leading to local system malfunction until repair. Also, the drain on the bathroom floor of many cruise ships may not have the S-shaped liquid-and-odor catch that one typically has in homes; this can occasionally cause the gases from a ship sewage collection tank to waft into the passenger compartment. These physical attributes of a ship’s plumbing suggest that aerated fecal matter could possibly get into passenger quarters. As this author understands, there are usually no bathroom vents to the outside, so what happens in the bathroom, in terms of gases, stays in the bathroom and cabin. Ship-wide air ventilation, or lack thereof, would also play a role in transmitting infection to others, via the respiratory or intestinal route. According to Shigeru Omi, an infectious disease prevention expert and former regional director for the World Health Organization, “On the ship, infections are getting very dense. ... It now provides a favorable environment for the virus to spread and I think it’s time for people to get off. … It’s like we are seeing a very condensed version of what could happen in a local community” (Feb. 13, [14]). The author’s recommendation: In near-term research, take each of the two possible infection routes seriously and examine the ships for such possibilities.

The cruise ships represent one example of “quarantine facilities.” New land-based quarantine facilities are being prepared far and wide, from China to the United States to Iceland and elsewhere. If the physics of the disease allow the types of fecal contamination spread we discuss here, then care must be taken with shared toilets, air circulation and personal hygiene to assure that “quarantine facilities” do not become “infection facilities” (or worse). Even ignoring the possible fecal route, it is widely known for respiratory infectious diseases such as influenza that air circulation, preferably with negative air pressure venting to the outside, is needed to minimize the risk of one infected person infecting others [15]. 

Not Just a Respiratory Disease

In summary, recorded events of January and February have demonstrated that the new COVID-19 virus is not just a respiratory disease. The virus may be expelled from a human with the disease via two routes: respiratory and intestinal. For intestinal, the virus-laden material may be any form of matter: solid, liquid or gas. Person-to-person respiratory spread by cough or sneeze usually requires the two interacting individuals to be close to one another, usually within two or three meters. Research and detective work on SARS 2003 have shown that the airborne plume of virus-laden diarrheic gases can spread very far, and it can linger.

Regarding our opening question, “What does it mean, ‘to be in contact with someone’”? Usually, with a respiratory disease, this means that two persons were together, within a few meters, for some (perhaps brief) period of time. If what we suggest here is found by additional research to be valid, then we must have an entirely new answer to this question. That is because “being in contact with someone” can mean using the same bathroom or toilet facility, perhaps many minutes or even an hour apart. Or, it could mean just breathing the air from a non-vented bathroom. Or, as we have seen, it could mean living in the same high-rise apartment building and sharing a faulty plumbing system.

If focused rapid research finds that the hypotheses offered here are valid, in whole or even in part, then many changes would be required in the current systems and procedures fighting this disease. These range from hyper vigilance aimed at bathroom and toilet cleanliness, to providing air circulation (preferably via negative air pressure vented to the outside) for the majority of patients, to redefining the parameters of quarantine and self-isolation.

Returning to SARS in 2003, this infectious disease was stopped not by a vaccine but by individuals acting in harmony to reduce frequency and intensity of contacts, using social distancing, improved hygiene and – when in doubt – self-isolation. Today, lacking a vaccine, it is likely that similar focused, diligent steps will be required to eradicate the COVID-19 virus.

Author’s qualifying statement

This article is an out-of-the-box think piece, dated Feb. 14, bolstered by historical evidence and some commonsense reasoning. It is not a refereed research paper and most of the ideas should be viewed as hypotheses, requiring further testing and research. Proven: Plumbing fumes from diarrhea from an infected person (SARS and the coronavirus) can/have spread the infection to others. Not proven: Public toilets or random flatus can spread the infection. Dilemma: How do individuals who test positive but have “no symptoms” spread the disease? My hypothesis: “No symptoms” means no respiratory symptoms, ignoring gastrointestinal distress.

The descriptions of cruise ship functioning derive from general publicly available literature and, since processes and designs continually change over time, do not necessarily pertain to any particular ship. We are still at the very early stages of the COVID-19 coronavirus epidemic, and much will be learned over coming days, weeks and months. 

To hear more about this article, listen to the Resoundingly Human podcast episode with author Richard Larson.


  1. “He Warned of Coronavirus. Here’s What He Told Us Before He Died,” The New York Times (Asia Pacific), Feb. 7, 2020.
  2. Ignatius Tak-Sun Yu, Hong Qiu, Lap Ah Tse and Tze Wai Wong, 2014, “Severe Acute Respiratory Syndrome Beyond Amoy Gardens: Completing the Incomplete Legacy,” Clinical Infectious Diseases, Vol. 58, No. 5, pp. 683-686.
  3. “Consensus document on the epidemiology of severe acute respiratory syndrome (SARS),” 2003, Department of Communicable Disease Surveillance and Response, World Health Organization, WHO/CDS/CSR/GAR/2003.11.
  4. Michelle L. Holshue, et al., 2020, “First Case of 2019 Novel Coronavirus in the United States,” New England Journal of Medicine, Jan. 31, 2020, doi:10.1056/NEJMoa2001191.
  5. Jason Gale, 2020, “Coronavirus Lurking in Feces May Reveal Hidden Risk of Spread,” Bloomberg, Feb. 1, https://www.bloomberg.com/news/articles/2020-02-01/coronaviruslurking-in-feces-may-reveal-hidden-risk-of-spread.
  6. Dawei Wang, Bo Hu, Chang Hu, et al., 2020, “Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China,” JAMA, published online Feb. 7, doi:10.1001/jama.2020.1585, http://bit.ly/2SNCV5a.
  7. Jiang Gu, et al., 2005, “Multiple organ infection and the pathogenesis of SARS,” Journal of Experimental Medicine, Vol. 202, No. 3, pp. 415-424 (Aug. 1), doi: 10.1084/jem.20050828.
  8. Hao Zhang, et al., 2020, “The digestive system is a potential route of 2019-nCov infection: a bioinformatics analysis based on single-cell transcriptomes,” bioRxiv preprint doi: https://doi.org/10.1101/2020.01.30.927806, https://www.biorxiv.org/content/10.1101/2020.01.30.927806v1.full.pdf.
  9. Danielle Dresden, 2018, “Ten facts about why we fart,” Medical News Today, May 21, https://www.medicalnewstoday.com/articles/321866.php.
  10. Jasper Fuk-Woo Chan, et al., 2020, “A family cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster,” The Lancet, Jan. 24, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30154-9/fulltext.
  11. “Infections in a Hong Kong building raise fears about how the virus spreads,” 2020, New York Times, Feb. 11, https://www.nytimes.com/2020/02/11/world/asia/coronavirus-china.html.
  12. Jayme Deerwester and Morgan Hines, 2020, “8 Americans on Princess cruise test positive for coronavirus on Guam bars Holland America ship,” USA TODAY, Feb. 7, https://www.usatoday.com/story/travel/news/2020/02/07/coronavirus-cruise-shipdenied-by-guam-japan-philippines-holland-america/4688716002/.
  13. Yaron Steinbuch, 2020, “65 new coronavirus cases confirmed on cruise ship docked in Japan,” New York Post, Feb. 10, https://nypost.com/2020/02/10/65-newcoronavirus-cases-confirmed-on-cruise-ship-docked-in-japan/.
  14. Mari Yamaguchi, 2020, “Japan reports 1st death from virus, 44 more cases on ship,” Associated Press, posted on Feb. 13, https://www.fox5vegas.com/news/us_world_news/japan-reports-more-cases-of-virus-on-quarantined-ship/article_ec654971-1cc2-56c2-8d73-0575661be7ba.html.
  15. Stan Finkelstein, Shiva Prakash, Karima Nigmatulina and Richard C. Larson, 2011, “A Home Flu ‘Kit’ to Empower Individuals and Families for Pandemic Flu,” Disaster Medicine and Public Health Preparedness, Vol. 5, No. 4, 2011. pp. 266-271.

Pandemics Past and Present

Nearly 15 years ago, spurred by the 2003 SARS outbreak and media reports of isolated cases of avian flu, members of a group within MIT’s School of Engineering focused on systems and policy engaged in discussions with colleagues about how to deploy operations research methods to mitigate the impact of an outbreak of contagious disease. As we were developing our research plan and forged collaborations with public health academics and emergency preparedness officials, lo and behold, we had a worldwide emergency on which to focus – the 2009 H1N1 flu pandemic was unfolding before our eyes.

Our multidisciplinary team of operations researchers and physicians, faculty and students poured over official reports from the Centers for Disease Control and Prevention, the World Health Organization and the media and used that information to develop stylized models of the spread of disease. The models were then used to test the effectiveness of alternative interventions – social distancing and behavioral changes, technology and novel approaches to vaccine allocation – to see what would be required to slow or stop the spread. We were excited to evaluate practical recommendations for low-cost home and workplace remedies – filtration, ventilation and temperature control – that attracted the attention of decision-makers in the public and private sectors.

– Dr. Stan Finkelstein, Harvard Medical School and Massachusetts Institute of Technology 


First-rank Operations Research

As of this writing, it is unclear how lethal the new coronavirus is to those who contract it. There have been more than 1,300 reported deaths among 60,000 infected people, which yields a raw death rate around 2%. That figure might be high because people with mild infections do not seek medical help. But it also could be low, because 7,000 virus sufferers are in critical condition. Already the deaths from the virus exceed the worldwide toll for the SARS outbreak.

Against this backdrop, articles like Professor Larson’s are extremely important. He raises the possibility that measures that reduce the respiratory spread of the virus might be considerably less effective than anticipated. Even if there is only a chance that his fears are realized, it could be prudent to take precautions with fecal waste. It would be irresponsible not to take his concerns seriously.

Professor Larson’s article exemplifies first-rank operations research. It reflects a rigorous review of the facts, a vigorous application of logic and common sense, intellectual audacity, and a recognition that strong OR/MS analysis need not involve elaborate mathematics. He understands that we cannot assume that the experts in an area know all there is to know and use that knowledge most effectively. When the eyes of operations researchers focus on a major problem, they often see vital things that would otherwise go unseen. We should follow his example and go out and look.

– Arnold Barnett, professor, Sloan School of Management, Massachusetts Institute of Technology


Richard C. Larson
([email protected])

Richard C. Larson is Mitsui Professor, Post-Tenure, in MIT’s Institute for Data, Systems and Society. A member of the National Academy of Engineering, Larson served as founding director of MIT LINC (http://linc.mit.edu) and is principal investigator of MIT BLOSSOMS (http://blossoms.mit.edu). Larson’s career has focused on operations research as applied to services industries (urban service systems, queueing, logistics, disaster management, disease dynamics, dynamic pricing of critical infrastructures, education and workforce planning). Larson’s research on pandemic influenza has been extensive, including a Best Paper of the Year award from the journal Value in Health (https://idss.mit.edu/staff/richard-larson/). He served as president of ORSA and INFORMS.

SHARE: Share on

INFORMS site uses cookies to store information on your computer. Some are essential to make our site work; Others help us improve the user experience. By using this site, you consent to the placement of these cookies. Please read our Privacy Statement to learn more.