Research
Projects
Sunlight Inactivation of Viruses in Water
Some enveloped viruses, like avian influenza, may be spread through contaminated environmental waters. The persistence of infectious viruses in water depends on many factors, however, including the presence of sunlight. Although we have a lot of information on short-wavelength, UVC light disinfection of viruses, this study was the first to provide quantitative data on sunlight inactivation of enveloped viruses in water.
The first part of this study (Key Findings, Publication) focused on infectious virus decay of two enveloped viruses and one non-enveloped virus. This study raised questions, however, about what the sunlight was targeting within the virus, if there was a clear distinction between enveloped and non-enveloped viruses, and the role of colored dissolved organic matter in indirect inactivation. We have expanded the project and are now addressing those additional questions (Key Objectives).
Collaborators
Kris McNeill, Environmental Systems Science at ETH Zürich
Bill Mitch, Environmental Engineering at Stanford University
Catherine Blish, Medicine - Infectious Diseases at Stanford University
Key Objectives
Identify key mechanisms of enveloped virus inactivation from sunlight, including genome, lipid, and protein degradation
Determine the inactivation rate of enveloped viruses given the presence of photosensitizers in colored natural water
Key Findings
The enveloped viruses tested decayed faster than the non-enveloped virus tested
Enveloped viruses were more susceptible to UVA and visible light versus the non-enveloped virus tested
Publication
Survival and Removal of Ascaris Suum from the Built Environment
Soil-transmitted helminths, like Ascaris, infect millions of people worldwide. Even with substantial drug treatment, they are endemic to Bangladesh. Ascaris infections may be so persistent because of their resilience in soil - they can survive years in soil and are virtually impossible to remove. When humans interact with the soil, they can then ingest Ascaris eggs and become infected.
To stop this cycle of transmission, what if we could remove the environmental intermediary? How would Ascaris eggs survive in a new environment - like on concrete? Could they be more easily removed? This study provides some of the first insights into Ascaris outside of soil environments. It will also help inform results from the ongoing Cement flooRs AnD chiLd hEalth (CRADLE) NIH trial in Bangladesh.
Collaborators
Jade Benjamin-Chung, Medicine - Epidemiology & Population Health at Stanford University
Key Objectives
Quantify the decay of Ascaris suum on concrete
Quantify the removal of Ascaris suum from concrete by mopping.
Developing Novel Microbial Source Tracking Markers
When pollution contaminates the environment from non-point sources, it is often difficult to track its origin. We are especially interested in mitigating microbial pollution from human sources, as human feces pose a higher risk to human health than animal feces. One way we can differentiate between sources is through microbial source tracking (MST) markers which use markers only found in human (or animal) gut microbiomes to identify the source of the pollution.
An ideal MST marker is specific to the origin of interest and reliable over time and space. Recently, two new phages were identified in the human gut microbiome - Hankyphage and LoVEphage. Could they be ideal MST markers?
Collaborators
Ami Bhatt, Medicine - Hematology at Stanford University
Key Objectives
Develop the MST markers
Test their performance using different sample types and a range of environmental conditions
Transfer rate of viruses between fingerpads and
surfaces
Surfaces (or fomites) can become contaminated with infectious viruses. When people come into contact with the viruses, they can transfer the viruses to their hands and can then innoculate themselves by touching their eyes, nose, or mouth. The transfer rate of viruses between hands and surfaces, however, is not well understood. Therefore, we cannot accurately predict the risk that viruses in the environment pose.
This study aims to develop a large-scale picture of virus transfer, investigating different variables like virus type, surface, time since last handwash, and direction of transfer. We used volunteers and plaque assays to measure infective viruses. This is one of the first large-scale data sets investigating the transfer of enveloped viruses between surfaces and fingerpads.
Key Findings
Both viruses were readily transferred, and the non-enveloped virus was transferred more frequently
The effect of the direction of transfer and surface type varied by virus
Handwashing did not affect the transfer rate of either virus
Publication
Transfer rate of enveloped and nonenveloped viruses between fingerpads and surfaces
Efficacy of Handwashing Methods Against Viruses
Handwashing has been proven to reduce the incidence of respiratory and gastrointestinal diseases and is especially important when pharmaceutical interventions, such as vaccines, are unavailable. Health programs like the CDC and WHO recommend handwashing for at least 20 seconds with soap and water, but what happens when you don't (or can't) follow those rules? Should we prioritize soap distribution? Should people turn to alcohol-based hand sanitizers? Is there a "one-size-fits-all" solution?
This study seeks to answer those questions and more in volunteer-based experiments with infective bacteriophages. It is one of the first studies to investigate the removal of enveloped viruses. Enveloped viruses, such as influenza and coronaviruses, are characterized by lipid membranes.
Collaborators
Marlene Wolfe, Environmental Health at Emory University
Key Findings
Wash your hands for at least 20 seconds - even if you don't have soap
Washing your hands for 20 seconds without soap was just as effective as washing with soap for both viruses tested
Washing your hands for 5 seconds was only effective for the enveloped virus tested
Use context-based interventions
Using hand sanitizer was only effective for enveloped viruses
Washing with a pre-made solution of powered soap and water was also as effective as regular soap and water use
Publication