Aerosol test for airborne bird flu developed

Recent outbreaks of highly pathogenic avian influenza have created a need for rapid and sensitive detection methods to mitigate its spread. Now, researchers have developed a prototype sensor that detects a type of influenza virus that causes bird flu (H5N1) in air samples. The low-cost sensor detects the virus at levels below an infectious dose and could lead to rapid aerosol testing for airborne avian influenza.

Bird flu can spread quickly when infectious respiratory droplets are inhaled by birds and other animals, and the virus’s frequent mutations make airborne transmission to humans a concern. Current methods to detect H5N1 viruses often require extensive sample preparation in a lab, such as polymerase chain reaction (PCR)-based tests. Therefore, a sensor that quickly detects these airborne viral particles without sample preparation could identify transmission before an outbreak occurs. One solution could be the electrochemical capacitive biosensor (ECB), which has been used to successfully detect other airborne viruses.

Previously, a research team led by Rajan Chakrabarty created an electrochemical biosensor to detect SARS-CoV-2 particles in breath. This time, the team from Washington University in St. Louis used ECB technology to detect and measure levels of H5N1 viruses in the air instead.

The new ECB consists of a thin network of Prussian blue nanocrystals and graphene oxide branches on a screen-printed carbon electrode. To make the sensor detect H5N1 viruses, the researchers attached probes (aptamers or antibodies) sensitive to these pathogens onto the network. They paired the sensor with a custom-built air sampler that pulls in droplets from the air and creates a liquid sample. When liquid samples containing H5N1 viruses were applied to the sensor, the viral particles bound to the probes and changed the sensor’s capacitance. By measuring the total change in capacitance, the researchers could measure the levels of H5N1 in the liquid sample.

In demonstrations with aerosolised samples containing known quantities of inactivated H5N1 viruses, the ECB produced results within 5 min. The sensor’s level of detection for avian influenza was 93 viral copies per 1 m³ of air — a level that should be sensitive enough to detect the presence of H5N1 below the virus’s infectious dose, the researchers claim. Furthermore, the sensor’s overall accuracy was over 90% when compared with measurements from a digital PCR test, the traditional method.

Chakrabarty and the team said the new bird flu sensor shows promise for non-invasive, real-time air monitoring for both animal and human populations. Their work has been published in the journal ACS Sensors.

Image caption: Co-authors Joseph Puthuserry, Yuezhi August Li, Joshin Kumar, Shu-Wen You and Professor Rajan Chakrabarty stand alongside the integrated H5N1 sampling-sensing unit that they developed. Photo courtesy of AIR lab.