Affordably tracking the transmission of respiratory infectious diseases in urban transport infrastructures can inform individuals about potential exposure to diseases and guide public policymakers to prepare timely responses based on geographical transmission in different areas in the city. Towards that end, we designed and tested a method to detect SARS-CoV-2 RNA in the air filters of public buses, revealing that air filters could be used as passive fabric sensors for the detection of viral presence. We placed and retrieved filters in the existing HVAC systems of public buses to test for the presence of trapped SARS-CoV-2 RNA using phenol-chloroform extraction and RT-qPCR. SARS-CoV-2 RNA was detected in 14% (5/37) of public bus filters tested in Seattle, Washington, from August 2020 to March 2021. These results indicate that this sensing system is feasible and that, if scaled, this method could provide a unique lens into the geographically relevant transmission of SARS-CoV-2 through public transit rider vectors, pooling samples of riders over time in a passive manner without installing any additional systems on transit vehicles.

Blood glucose measurement is commonly used to screen for and monitor diabetes, a chronic condition characterized by the inability to effectively modulate blood glucose that can lead to heart disease, vision loss, and kidney failure. Early detection of prediabetes can forestall or reverse more serious illness if healthy lifestyle adjustments or medical interventions are made in a timely manner. Current diabetes screening methods require visits to a healthcare facility and use of over-the-counter glucose-testing devices (glucometers), both of which are costly or inaccessible for many populations, reducing the chances of early disease detection. We therefore developed GlucoScreen, a readerless glucose test strip that enables affordable, single-use, at-home glucose testing, leveraging the user's touchscreen cellphone for reading and displaying results. By integrating minimal, low-cost electronics with commercially available blood glucose testing strips, the GlucoScreen prototype introduces a new type of low-cost, battery-free glucose testing tool that works with any smartphone, obviating the need to purchase a separate dedicated reader. Our key innovation is using the phone's capacitive touchscreen for the readout of the minimally modified commercially available glucose test strips. In an in vitro evaluation with artificial glucose solutions, we tested GlucoScreen with five different phones and compared the findings to two common glucometers, AccuChek and True Metrix. The mean absolute error (MAE) for our GlucoScreen prototype was 4.52 mg/dl (Accu-Chek test strips) and 3.7 mg/dl (True Metrix test strips), compared to 4.98 mg/dl and 5.44 mg/dl for the AccuChek glucometer and True Metrix glucometer, respectively. In a clinical investigation with 75 patients, GlucoScreen had a MAE of 10.47 mg/dl, while the AccuChek glucometer had a 9.88 mg/dl MAE. These results indicate that GlucoScreen's performance is comparable to that of commonly available over-the-counter blood glucose testing devices. With further development and validation, GlucoScreen has the potential to facilitate large-scale and lower cost diabetes screening. This work employs GlucoScreen's smartphone-based technology for glucose testing, but it could be extended to build other readerless electrochemical assays in the future.

Affordably tracking the transmission of respiratory infectious diseases in urban transport infrastructures can inform individuals about potential exposure to diseases and guide public policymakers to prepare timely responses based on geographical transmission in different areas in the city. Towards that end, we designed and tested a method to detect SARS-CoV-2 RNA in the air filters of public buses, revealing that air filters could be used as passive fabric sensors for the detection of viral presence. We placed and retrieved filters in the existing HVAC systems of public buses to test for the presence of trapped SARS-CoV-2 RNA using phenol-chloroform extraction and RT-qPCR. SARS-CoV-2 RNA was detected in 14% (5/37) of public bus filters tested in Seattle, Washington, from August 2020 to March 2021. These results indicate that this sensing system is feasible and that, if scaled, this method could provide a unique lens into the geographically relevant transmission of SARS-CoV-2 through public transit rider vectors, pooling samples of riders over time in a passive manner without installing any additional systems on transit vehicles.

Hypoxemia, a medical condition that occurs when the blood is not carrying enough oxygen to adequately supply the tissues, is a leading indicator for dangerous complications of respiratory diseases like asthma, COPD, and COVID-19. While purpose-built pulse oximeters can provide accurate blood-oxygen saturation (SpO2) readings that allow for diagnosis of hypoxemia, enabling this capability in unmodified smartphone cameras via a software update could give more people access to important information about their health. Towards this goal, we performed the first clinical development validation on a smartphone camera-based SpO2 sensing system using a varied fraction of inspired oxygen (FiO2) protocol, creating a clinically relevant validation dataset for solely smartphone-based contact PPG methods on a wider range of SpO2 values (70–100%) than prior studies (85–100%). We built a deep learning model using this data to demonstrate an overall MAE = 5.00% SpO2 while identifying positive cases of low SpO2 < 90% with 81% sensitivity and 79% specificity. We also provide the data in open-source format, so that others may build on this work.