Aerosolization of a Human Norovirus Surrogate, Bacteriophage MS2, during Simulated Vomiting

<div><p>Human noroviruses (NoV) are the leading cause of acute gastroenteritis worldwide. Epidemiological studies of outbreaks have suggested that vomiting facilitates transmission of human NoV, but there have been no laboratory-based studies characterizing the degree of NoV release during a vomiting event. The purpose of this work was to demonstrate that virus aerosolization occurs in a simulated vomiting event, and to estimate the amount of virus that is released in those aerosols. A simulated vomiting device was constructed at one-quarter scale of the human body following similitude principles. Simulated vomitus matrices at low (6.24 mPa*s) and high (177.5 mPa*s) viscosities were inoculated with low (10⁸ PFU/mL) and high (10¹⁰ PFU/mL) concentrations of bacteriophage MS2 and placed in the artificial “stomach” of the device, which was then subjected to scaled physiologically relevant pressures associated with vomiting. Bio aerosols were captured using an SKC Biosampler. In low viscosity artificial vomitus, there were notable differences between recovered aerosolized MS2 as a function of pressure (i.e., greater aerosolization with increased pressure), although this was not always statistically significant. This relationship disappeared when using high viscosity simulated vomitus. The amount of MS2 aerosolized as a percent of total virus “vomited” ranged from 7.2 x 10^-5 to 2.67 x 10^-2 (which corresponded to a range of 36 to 13,350 PFU total). To our knowledge, this is the first study to document and measure aerosolization of a NoV surrogate in a similitude-based physical model. This has implications for better understanding the transmission dynamics of human NoV and for risk modeling purposes, both of which can help in designing effective infection control measures.</p></div

Schematic of Simulated Vomiting Device.

<p><b>(</b>A) Diagram of the simulated vomiting device (B) Experimental set-up for capturing aerosolized virus.</p

Summary of Model Parameters, Assumptions, and Relevant Formulae used in Scaling the Simulated Vomiting Device.

<p>Assumptions:</p><p>(1) Flow through the human esophagus and machine esophagus was treated as flow through a smooth pipe.</p><p>(2) In some cases, the machine dimensions were rounded to the nearest available dimension offered by material manufacturers.</p><p>(3) The vomitus fluid inside the human body will be the same inside the vomiting machine; achieved by using surrogate vomitus with similar viscosities.</p><p>Summary of Model Parameters, Assumptions, and Relevant Formulae used in Scaling the Simulated Vomiting Device.</p

Aerosolization Experiments using bacteriophage MS2.

<p>Virus concentration “vomited” is designated by blue squares. Green diamonds show the amount of captured MS2 at designated pressures for simulated vomitus having low and high MS2 titer and of low and high viscosity. Error bars denote one standard deviation above the mean. Shared letters and symbols indicate treatments that were not statistically significantly different within each group.</p

Relationship between polyGT allele length and nausea sub-score.

<p>In patients with diabetic gastroparesis, the relationship between polyGT allele length and nausea sub-score on the GCSI questionnaire fit to a slope that was significantly different from zero (P < 0.006 by linear regression, dotted lines are 95% confidence intervals) and b) subjects with one or two long alleles (open circles in Fig 4a) had significantly higher nausea sub-scores than subjects with zero long alleles (closed circles in Fig 4a, P = 0.022, Mann Whitney test). Whiskers are the medians with the interquartile ranges for the nausea sub-score.</p

Size distribution of the polyGT repeat lengths.

<p>a) The size distribution of the polyGT repeat length in type 2 diabetic controls is significantly longer than the allele length in non-diabetic controls. The fractional frequency distribution of the lengths of polyGT repeat in <i>HMOX1</i> from non-diabetic control subjects with no GI motility disorders (n = 170) compared to subjects with type 2 diabetes and no GI motility disorders (n = 84) are shown (P < 0.05 Dunn’s test). b) Fractional frequency distribution of the lengths of polyGT repeat in <i>HMOX1</i> from subjects with type 2 diabetes and no GI motility disorders (n = 84) compared to subjects with type 2 diabetes and gastroparesis (n = 72, P = NS, Dunn’s test). c) Fractional frequency distribution of the lengths of polyGT repeat in <i>HMOX1</i> from subjects with type 1 diabetes and no GI motility disorders (n = 84) compared to subjects with type 1 diabetes and gastroparesis (n = 99, P = NS, Dunn’s test). Allele length was determined by PCR amplification of genomic DNA from blood using the ABI 3730 platform and capillary electrophoresis and using primers flanking the GT repeat region.</p

Data on gastroparetic subjects that were studied.

<p>Data on gastroparetic subjects that were studied.</p