Scientists use ultrasound to destroy influenza A and COVID-19 viruses without damaging human cells

Researchers at the University of São Paulo (USP) in Brazil have discovered that high-frequency ultrasound waves similar to those used in medical exams can eliminate viruses such as SARS-CoV-2 and H1N1 without damaging human cells. In an article published in Scientific Reports, they described how the phenomenon, known as acoustic resonance, causes structural changes in viral particles until they rupture and become inactivated.

“It’s kind of like fighting the virus with a shout. In this study, we proved that the energy of sound waves causes morphological changes in viral particles until they explode, a phenomenon comparable to what happens with popcorn. By degrading the structure of the pathogen, the protective membrane of the virus [called the envelope] bursts and deforms, preventing the virus from invading human cells,” explains Odemir Martinez Bruno, a professor at the São Carlos Institute of Physics (IFSC) at USP who coordinated the study.

Ultrasound-mediated inactivation of enveloped viruses opens up a new treatment possibility for viral diseases. In fact, the team is already conducting in vitro tests against other infections, such as dengue, Chikungunya, and Zika. This alternative treatment is particularly interesting given that antiviral drugs are generally difficult to develop.

“Although it’s still far from clinical use, this is a promising strategy against enveloped viruses in general, since developing chemical antivirals is complex and yields difficult results. Furthermore, it’s a ‘green’ solution, as it generates no waste, causes no environmental impact, and doesn’t promote viral resistance,” says Flávio Protásio Veras, a professor at the Federal University of Alfenas (UNIFAL) and a FAPESP postdoctoral fellow. FAPESP funded the work through projects 20/05601-6, 23/07241-5, 13/08216-2, 19/26119-0, 18/22214-6 and 21/08325-2. 

The research brought together scientists from various fields. In addition to theoretical physicists and acousticians from the IFSC, the initiative benefited from the collaboration of specialists from the Virology Research Center and the Center for Research in Inflammatory Diseases (CRID), both affiliated with the Ribeirão Preto Medical School (FMRP-USP), the School of Pharmaceutical Sciences (FCFRP-USP), and the Faculty of Science and Technology at São Paulo State University (UNESP). These specialists contributed structural and toxicological analyses using techniques such as microscopy and light scattering.

The initiative also benefited from the collaboration of Charles Rice, a professor at Rockefeller University in the United States and the 2020 Nobel Prize winner in medicine. Rice provided fluorescent viruses for real-time visualization.

It’s the geometry

The discovery surprised the researchers because it contradicts classical physics theories, as the wavelength of ultrasound is much longer than the size of the virus. In theory, this difference in size would prevent interaction.

“The phenomenon is entirely geometric. Spherical particles, such as many enveloped viruses, absorb ultrasound wave energy more effectively. It’s that accumulation of energy inside the particle that causes changes in the structure of the viral envelope until it ruptures. Therefore, if viruses were triangular or square, they wouldn’t undergo the same ‘popcorn effect’ of acoustic resonance,” Bruno explains.

He also points out that since the process depends strictly on the shape of the viral particle and not on genetic mutations, variants such as those observed during the pandemic (Omicron and Delta, for example) do not affect the effectiveness of the technique.

Frequency adjustment

“The technique isn’t intended for decontamination. That already exists. Ultrasound is already used to sterilize dental and surgical equipment, but it works through a different physical phenomenon called cavitation, which destroys biological material,” says Bruno.

He explains that acoustic resonance and cavitation differ mainly in the frequency used and their effects on viruses and cells. “While cavitation occurs at low frequencies and destroys both viruses and tissues through the collapse of gas bubbles, acoustic resonance operates at high frequencies [3–20 MHz],” he notes.

Regarding acoustic resonance, Bruno explains that sound energy couples with the viral structure, exciting internal vibrations that lead to the mechanical rupture of the viral envelope without altering the temperature or pH of the medium. “The result is a selective and safe mechanism since only the virus absorbs the energy and is destabilized, posing no risk to human cells,” he adds.

Another scientific article published in the Brazilian Journal of Physics describes the theoretical basis behind the phenomenon of popping enveloped viruses like popcorn. 

About FAPESP

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the state of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration.