Coronaviruses may be vulnerable to ultrasound vibrations, within the frequencies used in medical diagnostic imaging, said researchers.

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Through computer simulations, the team modelled the virus' mechanical response to vibrations across a range of ultrasound frequencies and found that vibrations between 25 and 100 megahertz triggered the virus' shell and spikes to collapse and start to rupture within a fraction of a millisecond. This effect was seen in simulations of the virus in the air and in water, said the researchers, including Tomasz Wierzbicki from the Massachusetts Institute of Technology.

"We've proven that under ultrasound excitation the coronavirus shell and spikes will vibrate, and the amplitude of that vibration will be very large, producing strains that could break certain parts of the virus, doing visible damage to the outer shell and possibly invisible damage to the RNA inside," said Wierzbicki. The coronavirus' structure is an all-too-familiar image, with its densely packed surface receptors resembling a thorny crown, the team said.

These spike-like proteins latch onto healthy cells and trigger the invasion of viral RNA. While the virus' geometry and infection strategy is generally understood, little is known about its physical integrity. For the study, published in the Journal of the Mechanics and Physics of Solids, the team introduced acoustic vibrations into the simulations and observed how the vibrations rippled through the virus' structure across a range of ultrasound frequencies. The team started with vibrations of 100 megahertz, or 100 million cycles per second, which they estimated would be the shell's natural vibrating frequency, based on what's known of the virus' physical properties.

When they exposed the virus to 100 MHz ultrasound excitations, the virus' natural vibrations were initially undetectable. But within a fraction of a millisecond the external vibrations, resonating with the frequency of the virus' natural oscillations, caused the shell and spikes to buckle inward, similar to a ball that dimples as it bounces off the ground. As the researchers increased the amplitude, or intensity, of the vibrations, the shell could fracture -- an acoustic phenomenon known as a resonance that also explains how opera singers can crack a wineglass if they sing at just the right pitch and volume.

At lower frequencies of 25 MHz and 50 MHz, the virus buckled and fractured even faster, both in simulated environments of air and of water that is similar in density to fluids in the body.