JP7820122B2 - Infection Risk Assessment System - Google Patents

Description

The present invention relates to an infection risk assessment system and an infection risk assessment method.

In order to reduce the risk of infection from patients infected with pathogens, it is necessary to accurately understand the infection risk based on the spread of the pathogen and to develop countermeasures.
Therefore, various methods have been developed to analyze the diffusion of substances emitted from patients.

For example, Patent Document 1 proposes a system that detects water droplets dispersed using a simulated cough airflow generator using water-sensitive paper coated to change color when exposed to water droplets.
The method in Patent Document 1 makes it possible to assess to some extent the risk of droplets (mainly saliva) emitted by the patient scattering and adhering to other people in close proximity or to surfaces such as surrounding furniture, causing droplet infection.

However, the method of Patent Document 1 cannot evaluate the risk of so-called microdroplet infection (aerosol infection), which is infection caused by inhaling droplet nuclei (microdroplets) with small particle diameters floating in the air.
Larger pathogens tend to fall to the ground, reducing the risk of infection, but smaller particles can remain suspended in the air for long periods of time. These small particles that can remain suspended in the air for long periods of time are called droplet nuclei (microdroplets).

One possible method for evaluating microdroplet infection is airflow measurement, which has been widely used in analyzing indoor temperature and humidity control, etc. However, while airflow measurement can visualize airflow, it cannot quantify the number of particles emitted by an infected person that reach a target area.
In addition, by spraying standard particles such as latex or polystyrene with a size of 5 μm or less, it is possible to quantify the number of particles that reach the target location from the spraying point. However, since latex and polystyrene cannot be distinguished from indoor particles outside of a clean room, they can only be used in an unmanned clean room or chamber.

Because fluctuations in carbon dioxide concentration are largely due to carbon dioxide emitted by humans, it is used as a simple indicator of the number of people indoors. While it can be used as a guide to assess the risk of infection due to the number of people, it cannot be used to identify the route of infection transmission.
Computer simulations can predict how many particles emitted by a patient will reach a specific location in a room, but they are costly because a model must be created for each room, and they have many limitations, such as the increased computational load and the inability to complete the calculations when the conditions increase or the evaluation time becomes longer.

JP 2014-137754 A

In light of the above circumstances, the present invention aims to provide an infection risk assessment system and method that can quantitatively assess, at each assessment point in an actual facility, the amount of droplet nuclei generated by coughing, etc., that reach that point, and how the amount of droplet nuclei changes over time.

In order to achieve the above object, the present invention employs the following configuration.
[1] A particle spray device that sprays fluorescent particles that emit fluorescence when irradiated with excitation light by simulating coughing or sneezing;
an analyzer for detecting the fluorescent particles;
An infection risk assessment system comprising: a sampling tube that draws gas from one or more assessment points and supplies it as sample gas to the analytical device.
[2] The analytical device is an infection risk assessment system described in [1], which has a detection tube through which the sample gas flows, an excitation light source that irradiates excitation light onto aerosol particles in the sample gas in the detection tube, and a fluorescence detection unit that detects fluorescence emitted from the aerosol particles by the excitation light.
[3] The infection risk assessment system described in [2], wherein the analytical device further has a scattered light detection unit that detects the excitation light scattered by the aerosol particles.
[4] Fluorescent particles that emit fluorescence when irradiated with excitation light are sprayed from one or more simulated droplet generation locations, simulating coughing or sneezing,
aspirating gas from one or more evaluation points and supplying the gas as a sample gas to an analyzer that detects the fluorescent particles;
An infection risk assessment method for assessing the arrival status of the fluorescent particles at the assessment point based on the detection results of the analysis device.
[5] The infection risk assessment method described in [4], wherein the detection result of the analysis device is the number of fluorescent particles detected per unit time.
[6] The infection risk assessment method described in [4], wherein the detection result of the analytical device is an integrated value of fluorescence intensity per unit time.
[7] The infection risk assessment method according to any one of [4] to [6], wherein the fluorescent particles are particles of lactose to which a fluorescent substance is attached.
[8] The infection risk assessment method described in [7], wherein the fluorescent substance is riboflavin.
[9] An infection risk assessment method described in any one of [4] to [7], wherein there are multiple simulated droplet generation locations, and the fluorescent particles sprayed from each simulated droplet generation location are particles containing fluorescent substances with different fluorescent wavelengths.

The infection risk assessment system and infection risk assessment method of the present invention make it possible to quantitatively assess, at each assessment point in an actual facility, the amount of droplet nuclei generated by coughing, etc. that reach a given point, and how the amount of droplet nuclei changes over time.

1 is a schematic configuration diagram of an infection risk assessment system according to one embodiment of the present invention. 1 is a schematic diagram showing an example of a particle spraying device used in the present invention. FIG. 1 is an explanatory diagram showing an example of a mode of use of a particle spray device used in the present invention. FIG. 1 is a schematic diagram showing an example of an analytical device used in the present invention. FIG. 1 is an explanatory diagram of a test method used in an example. FIG. 10 is a graph showing the change over time in the number of particles obtained in the example.

<Infection risk assessment system>
An infection risk assessment system according to one embodiment of the present invention will be described with reference to FIG.
The infection risk assessment system of this embodiment comprises a particle spray device 10, an analysis device 70, a first sampling pipe 63 that sucks gas from a first evaluation point 61 and supplies it to the analysis device 70, and a second sampling pipe 64 that sucks gas from a second evaluation point 62 and supplies it to the analysis device 70.

The infection risk assessment system of this embodiment further includes a clean air cylinder 65, a cleaning pipe 66 that supplies clean air from the clean air cylinder 65 to the analysis device 70, a sample changer 67 that switches between the first sampling pipe 63, the second sampling pipe 64, and the cleaning pipe 66 and connects them to the analysis device 70, and a computing device 80.

In this embodiment, a first evaluation point 61 is set in a simulated coughing area 100 (such as a hospital room where a patient is present), which is located in the same room as the particle spray device 10. In addition, a second evaluation point 62 is set in an isolated area 200 (such as a nurse's station) isolated from the simulated coughing area 100.

The analysis device 70, computing device 80, clean air cylinder 65, and sample changer 67 are installed in the isolation area 200, and the first sampling pipe 63 passes from the simulated cough occurrence area 100 through a wall separating the simulated cough occurrence area 100 and the isolation area 200 and is connected to the sample changer 67 in the isolation area 200.

The particle spray device 10 is not limited to a specific configuration as long as it can spray particles by simulating a cough or sneeze, but for example, one with a configuration shown in FIG. 2 can be used.
The particle spray device 10 shown in Figure 2 comprises a particle containing cartridge 20, a compressor 31 that supplies compressed air to the particle containing cartridge 20, an air supply pipe 32 that connects the compressor 31 and the particle containing cartridge 20, and an electromagnetic valve 33 provided in the air supply pipe 32.

The particle storage cartridge 20 includes an outer cylinder 21, a cylindrical inner cylinder 22 with a bottom disposed inside the outer cylinder 21, a lid 23 that closes the upper end opening of the inner cylinder 22, a gas introduction pipe 25 that passes through the lid 23 and has a tip that reaches near the bottom of the inner cylinder 22, and a connector 26 for connecting an air supply pipe 32 to the gas introduction pipe 25. The lid 23 is provided with a plurality of ejection ports 24.
The fluorescent particles 40 to be sprayed are accommodated in the bottom of the inner cylinder 22 .

The pressure when the solenoid valve 33 is opened and the time for which the open state is maintained can be adjusted as appropriate.
The particle storage cartridge 20 can generate an airflow that simulates a cough or sneeze by operating the compressor 31 differentially and opening the solenoid valve 33 for a predetermined time under set pressure conditions.

The generated air flow passes through the air supply pipe 32 and the gas introduction pipe 25 and is blown onto the fluorescent particles 40 contained in the bottom of the inner cylinder 22 of the particle-containing cartridge 20. The fluorescent particles 40 are blown up inside the outer cylinder 21 by the blowing of this air flow, and are sprayed outward from the nozzle 24 together with the air flow.
3, the particle-containing cartridge 20 can also be placed in the mouth 51 of a thermal manikin 50. Using the thermal manikin 50 makes it possible to perform tests that simulate the airflow after spraying, taking into account the influence of the patient's body temperature.

The analytical device 70 can be configured, for example, as shown in FIG. 4. The analytical device 70 in FIG. 4 includes a detection tube 71 through which sample gas flows, an excitation light source 72 that irradiates excitation light onto aerosol particles in the sample gas within the detection tube 71, and a fluorescence detection unit 73 that detects fluorescence emitted from aerosol particles in the sample gas within the detection tube 71. The analytical device 70 of this embodiment further includes a scattered light detection unit 74 that detects excitation light scattered by aerosol particles in the sample gas within the detection tube 71. It also includes a signal processing device (not shown) that processes signals obtained from the fluorescence detection unit 73 and the scattered light detection unit 74 to obtain data to output to the computing device 80.

The wavelength of the excitation light emitted from the excitation light source 72 is selected appropriately depending on the type of fluorescent substance contained in the fluorescent particles 40. For example, when riboflavin is used as the fluorescent substance, the wavelength of the excitation light can be around 400 nm. Furthermore, the excitation light source 72 is selected appropriately so as to emit excitation light of the required wavelength. For example, a Xe flash lamp (xenon discharge tube), a D2 lamp (deuterium discharge tube), etc. can be used.

The detection wavelength of the fluorescence detection unit 73 is appropriately selected depending on the type of fluorescent substance contained in the fluorescent particles 40. For example, when riboflavin is used as the fluorescent substance, the detection wavelength of the fluorescence can be in the wavelength range of 420 to 600 nm.
A photomultiplier tube, a photodiode, a phototransistor, an avalanche photodiode, etc. may be appropriately used as the fluorescence detection unit 73. In addition, in order to cut light other than fluorescence, for example, wavelengths of excitation light, optical members such as a cut filter and a diffraction grating may be appropriately combined and used.

The fluorescence detection unit 73 is preferably installed in a position where it is not reached by Mie scattered light (excitation light scattered by aerosol particles). In this embodiment, the fluorescence detection unit 73 is positioned diagonally across the detection tube 71 from the excitation light source 72. Since the fluorescence emitted within the detection tube 71 is emitted in all directions, in the example of Figure 4, a collecting mirror 75 is used to capture fluorescence heading in a direction different from the fluorescence detection unit 73 and collect it in the fluorescence detection unit 73.

The detection wavelength of the scattered light detection unit 74 is the wavelength of the excitation light emitted from the excitation light source 72 .
A photomultiplier tube, a photodiode, a phototransistor, an avalanche photodiode, etc. can be appropriately used as the scattered light detection unit 74. In addition, in order to cut out light other than the scattered excitation light, optical members such as a cut filter and a diffraction grating can be appropriately combined and used.

There are no particular limitations on the positional relationship of the scattered light detection unit 74 with respect to the excitation light source 72, but in the analysis device 70 of Figure 4, the scattered light detection unit 74 is positioned on the optical axis of the excitation light source 72, on the opposite side of the detection tube 71 from the excitation light source 72. In other words, it is designed to detect forward scattering due to Mie scattering.

A shielding plate 76 is provided to prevent the excitation light that has traveled straight along the optical axis of the excitation light source 72 without being scattered from the excitation light source 72 from reaching the scattered light detection unit 74 .
Furthermore, a collimating lens 77 is disposed adjacent to the shielding plate 76 on the optical axis in front of the shielding plate 76, and a condenser lens 78 is disposed at a position slightly spaced apart from the collimating lens 77. The excitation light scattered by the aerosol particles and deviated from the optical axis passes outside the shielding plate 76, is collimated by the collimating lens 77, and is then collected by the condenser lens 78 into the scattered light detection unit 74.

By detecting forward scattering due to Mie scattering, the scattered light detection unit 74 can detect that aerosol particles have passed through the detection tube 71. Therefore, by processing the signal from the scattered light detection unit 74, the analysis device 70 can obtain data proportional to the number of aerosol particles in the sample gas passing through the detection tube 71 per unit time.

Furthermore, by detecting the fluorescence, the fluorescence detection unit 73 can detect that aerosol particles emitting fluorescence have passed through the detection tube 71. Therefore, by processing the signal from the fluorescence detection unit 73, the analysis device 70 can obtain a number proportional to the number of aerosol particles emitting fluorescence in the sample gas passing through the detection tube 71 per unit time.
Furthermore, it is also possible to obtain the integrated value of the fluorescence intensity per unit time from inside the detection tube 71 as data.

The analysis device 70 processes the signal from the scattered light detection unit 74 to determine a number proportional to the number of aerosol particles in the sample gas passing through the detection tube 71 per unit time, and processes the signal from the fluorescence detection unit 73 to determine a number proportional to the number of fluorescent aerosol particles in the sample gas passing through the detection tube 71 per unit time. By calculating the ratio of the latter to the former, it is possible to obtain data representing the ratio of the number of fluorescent aerosol particles detected per unit time to the number of aerosol particles detected per unit time.

The analytical device 70 also processes the signal from the scattered light detection unit 74 to determine a number proportional to the number of aerosol particles in the sample gas passing through the detection tube 71 per unit time, and processes the signal from the fluorescence detection unit 73 to determine the integrated value of the fluorescence intensity per unit time from within the detection tube 71. By calculating the ratio of the latter to the former, it is possible to obtain data that correlates with the proportion of fluorescent aerosol particles in the sample gas.

Commercially available devices that can be used as the analytical device 70 include, for example, the Instantaneous Microbial Detection ^™ real-time bacterial detector manufactured by BioVigilant Systems, the Ultraviolet Aerodynamic Particle Sizer (Model 3314) manufactured by TSI, and the BioTrak real-time microbiological measuring instrument (Model 9510-BD) manufactured by TSI.
Among these, the real-time bacteria detector manufactured by Bio Vigilant Systems is preferred because it can detect 0.7 femtog (0.7×10 ⁻¹⁵ g) of riboflavin attached to the surface of lactose particles and can perform extremely accurate analysis.

The data obtained by the analysis device 70 is sent to the calculation device 80 .
The computing device 80 can quantitatively evaluate the arrival status of droplet nuclei at a specific first evaluation point 61 within the simulated cough occurrence area 100 based on data obtained while the sample changer 67 connects the first sampling tube 63 to the analysis device 70. Also, the computing device 80 can quantitatively evaluate the arrival status of droplet nuclei at a specific second evaluation point 62 within the isolation area 200 based on data obtained while the sample changer 67 connects the second sampling tube 64 to the analysis device 70.

Furthermore, by connecting the cleaning tube 66 to the analyzer 70 via the sample changer 67, the inside of the detection tube 71 of the analyzer 70 can be cleaned with clean air. This prevents fluorescent particles 40 remaining in the detection tube 71 when the sample changer 67 connects one of the sampling tubes to the analyzer 70 from affecting the measurement results when another sampling tube is subsequently connected to the analyzer 70.

<Infection risk assessment method>
The infection risk assessment method of the present invention is a method in which fluorescent particles that emit fluorescence when irradiated with excitation light are sprayed from one or more simulated droplet generation locations to simulate coughing or sneezing, gas is then aspirated from one or more assessment locations and supplied as sample gas to an analysis device that detects the fluorescent particles, and the arrival status of the fluorescent particles at the assessment locations is assessed based on the detection results of the analysis device.
The infection risk assessment method of the present invention can be carried out using, for example, the infection risk assessment system described with reference to FIGS.

The fluorescent particles 40 are particles that emit fluorescence when irradiated with excitation light. The size of the fluorescent particles 40 can be set appropriately depending on the size of the particles to be evaluated. When evaluating the risk of microdroplet infection, it is preferable to use fluorescent particles of a small size that can remain suspended in the air for a long period of time.
Specifically, the particle size of the fluorescent particles 40 is preferably 0.01 to 100 μm, more preferably 0.1 to 50 μm, and even more preferably 0.5 to 30 μm.
It is also possible to mix fluorescent particles 40 of different sizes, or to use fluorescent particles 40 with a particle size distribution.

The fluorescent particles 40 are preferably carrier particles to which a fluorescent substance is attached.
The carrier particles are preferably excipients added to improve the handling or formulation of pharmaceuticals, pesticides, etc., or to facilitate administration. Since excipients are non-toxic, they can be used in places where patients and medical personnel are present, such as actual hospitals.
Excipients include lactose (milk sugar), starch, dextrin, sucrose (cane sugar), glucose (grape sugar), precipitated silica, and the like.

It is also preferable that the carrier particles are water-soluble. If the carrier particles are water-soluble, the fluorescent particles 40 can be removed using a humidifier. For example, by installing a humidifier in the duct of an air conditioning system, it is possible to remove the fluorescent particles 40 returning from the air conditioning system to the room, and to evaluate only the particle propagation within the room.
Examples of water-soluble carrier particles include lactose (milk sugar), soluble starch, dextrin, saccharose (cane sugar), glucose (grape sugar), and the like.
As the carrier particles, lactose, which is commonly used as an excipient, is particularly preferred.

There are no particular limitations on the fluorescent substance, as long as it emits fluorescence when irradiated with excitation light. Since it is not limited to certain locations for use, it is preferable that the substance is harmless to the human body. For example, riboflavin (vitamin _B2 ) is a water-soluble vitamin that is harmless to the human body and is therefore preferred.
Fluorescent substances other than riboflavin include NADH, aromatic amino acids (tryptophan, tyrosine, phenylalanine), coumarin, and the like.
As the fluorescent particles 40, particles in which riboflavin is attached to lactose are particularly preferred.

It is also possible to use multiple types of fluorescent particles 40 containing fluorescent substances with different fluorescent wavelengths. For example, when multiple simulated droplet generation locations are provided where the particle spray device 10 is installed and fluorescent particles 40 are sprayed, if fluorescent particles 40 containing fluorescent substances with different fluorescent wavelengths are used for each simulated droplet generation location, it is possible to determine from which simulated droplet generation location fluorescent particles 40 detected at a specific evaluation point arrived.
Furthermore, if fluorescent particles 40 are made by mixing carrier particles of different sizes to which fluorescent substances with different fluorescent wavelengths are attached, particle propagation for each particle size can also be evaluated.

The fluorescent substance of the fluorescent particles 40 is preferably attached to the surface of the carrier particles. When riboflavin is attached to the surface of lactose particles, the mass of riboflavin relative to the mass of lactose is preferably 0.001 to 1% by mass, and more preferably 0.01 to 0.1% by mass.

When the ratio of the mass of riboflavin to the mass of lactose is equal to or greater than the lower limit of the preferred range, fluorescence can be sufficiently detected using the commercially available analytical device described above. When the ratio of the mass of riboflavin to the mass of lactose is equal to or less than the upper limit of the preferred range, the amount of expensive fluorescent substance used is not excessive, and the evaluation method of the present invention can be carried out while keeping costs down.

Methods for uniformly attaching fluorescent material to the surface of carrier particles include coating the entire surface of the carrier particles with fluorescent material, and attaching the fluorescent material to the surface of the carrier particles by a method other than coating.

In the method of coating the fluorescent material over the entire surface of the carrier particles, a part of the coated fluorescent material may be impregnated into the interior of the carrier particles.
To coat the entire surface of the carrier particles with the fluorescent substance, first prepare a solution in which the fluorescent substance is dissolved in a solvent at a predetermined concentration, and then apply the solution uniformly to the surface of the carrier particles. The application method is not particularly limited, and examples that can be used include mixing the solution in which the fluorescent substance is dissolved at a predetermined concentration with an excipient, or spraying the solution in which the fluorescent substance is dissolved at a predetermined concentration onto the carrier particles.
The amount of the fluorescent substance used for coating is preferably 0.001 to 1% by mass, more preferably 0.01 to 0.1% by mass, relative to the carrier particles.

Next, the solvent of the solution is removed, leaving the fluorescent substance, which is the solute of the solution, on the surface of the carrier particles, thereby obtaining the desired composite particles.
Examples of devices for mixing a solution in which a fluorescent substance is dissolved at a predetermined concentration with carrier particles and then removing the solvent include a pan coating device, a tumbling coating device, and a fluidized bed coating device.

In a method for attaching a fluorescent substance to the surface of a carrier particle by a method other than coating, it is preferable to attach (fix) the fluorescent substance relatively strongly to the surface of the carrier particle.
Methods for producing composite particles in which the fluorescent substance is relatively weakly attached to the surface of the carrier particles include a mixing method in which the carrier particles and the fluorescent substance are mixed while stirring using a mill or the like, a mixing method using a fluidized bed method, and a mixing method using a high-speed compression/shear type mixer.

Dry particle composite technology is one method that can adhere fluorescent material relatively strongly to the surface of carrier particles. With this technology, carrier particles dispersed in a high-speed airflow and fluorescent material are collided with each other, and the carrier particles and fluorescent material are dry-bonded (fixed) together primarily by the impact force of the collision, allowing the fluorescent material to adhere so that it covers all or at least part of the surface of the carrier particles.

By using dry particle composite technology, it is possible to form a film made of a fluorescent material on the surface of carrier particles by appropriately adjusting the conditions during collision. During this film formation, the shape of the fluorescent material before collision can be maintained, or the shape of the fluorescent material can be deformed by the collision energy. Basically, the shape and particle size of the carrier particles before collision can be maintained even after collision (composite formation).
When using the dry particle composite technology, it is preferable to finely pulverize the fluorescent material to a predetermined size in advance. After pulverization, the particle size of the fluorescent material is preferably 1 μm or less, and more preferably 0.01 to 0.1 μm.

When forming composite particles using dry particle composite technology, the chamber in which the carrier particles and fluorescent material collide is dried and cooled, and the chamber is filled with an inert gas atmosphere such as nitrogen gas or argon gas. This suppresses thermal and oxidative decomposition of the fluorescent material that makes up the child particles, preventing a loss of detection sensitivity for the composite particles. This composite method can be carried out using known commercially available equipment (e.g., a hybridizer manufactured by Nara Machinery Works, Ltd., or a Mechanofusion System manufactured by Hosokawa Micron Corporation).

The airflow used to spray the fluorescent particles 40 is an airflow that simulates a cough or sneeze. Specifically, the electromagnetic valve 33 adjusts the pressure and air supply time to produce an airflow that is similar to a cough or sneeze.
Since the strength of the cough varies depending on the type of illness and the patient's condition, the specific pressure and time for air delivery may be adjusted appropriately depending on the purpose of evaluation.
To create an airflow that mimics a typical cough, the pressure is preferably 0.2 to 0.5 MPa, more preferably 0.3 to 0.4 MPa, and the air supply time is preferably 0.1 to 0.5 seconds, more preferably 0.2 to 0.3 seconds.

The fluorescent particles 40 are detected in the analysis device 70 as fluorescent aerosol particles (a state in which the fluorescent particles 40 are dispersed as a dispersed phase in air as a continuous phase).
Although dust particles and the like in the air are also present as a dispersed phase in the sample gas, the fluorescent particles 40 can be distinguished from the dust particles and the like by emitting fluorescence.

The analysis device 70 inputs one or more of the following data to the calculation device 80, and the calculation device 80 acquires the data.
1) The number of fluorescent particles detected per unit time (a number proportional to the number of fluorescent particles 40 in the sample gas passing through the detection tube 71 per unit time).
2) Integrated value of fluorescence intensity per unit time (integrated value of fluorescence intensity based on fluorescent particles 40 in the sample gas passing through the detection tube 71 per unit time).
3) The ratio of the number of fluorescent particles detected per unit time to the total number of particles detected per unit time (the ratio of the number proportional to the number of particles, including dust, in the sample gas passing through the detection tube 71 per unit time to the number proportional to the number of fluorescent particles 40 in the sample gas passing through the detection tube 71 per unit time).
4) The ratio of the integrated value of the fluorescence intensity per unit time to the total number of particles detected per unit time (the ratio of the integrated value of the fluorescence intensity based on the fluorescent particles 40 in the sample gas passing through the detection tube 71 per unit time to a number proportional to the number of particles, including dust, in the sample gas passing through the detection tube 71 per unit time).

If the analysis device 70 does not have the scattered light detection unit 74, it can generate the data 1) or 2) above, but cannot generate the data 3) or 4) above.
The analysis device 70 has the scattered light detection unit 74, and thus can generate the data 3) or 4) above in addition to the data 1) or 2) above.

The data in 3) above is the number of fluorescent particles detected per unit time, similar to the data in 1), but is normalized by the total number of particles detected per unit time.
The data in 4) above is an integrated value of the fluorescence intensity per unit time, similar to the data in 2) above, but is normalized by the total number of particles detected per unit time.
The data in 3) or 4) above is not easily affected by fluctuations in the flow rate of the sample gas introduced into the detection tube 71.

The computing device 80 can quantitatively evaluate the arrival status of the fluorescent particles 40 at the evaluation point based on the data received from the analyzing device 70 .
Furthermore, if gas is aspirated and analyzed at the same evaluation point at different times, it is possible to confirm the change over time in the amount of fluorescent particles 40 at that evaluation point.

There are no particular restrictions on the order in which the sample changer 67 connects the flow paths to the analysis device 70. However, if one sampling tube, for example, the first sampling tube 63, is connected and then another sampling tube, for example, the second sampling tube 64, is connected, it is preferable to connect the cleaning tube 66 before connecting to the second sampling tube 64, and allow clean air from the clean air cylinder 65 to flow into the detection tube 71 of the analysis device 70. This can improve the accuracy of the analysis.

There are no particular limitations on the setting of the evaluation point, but if a simulated cough occurrence area 100 is selected, such as the first evaluation point 61 in Figure 1, it is possible to evaluate, for example, the effectiveness of indoor ventilation. For example, if it is found that the amount of fluorescent particles 40 does not decrease over time at the detection point in an actual hospital room where a patient is present, this indicates a problem with indoor ventilation and measures such as issuing an alarm can be taken.

Furthermore, by selecting an isolation area 200, such as a nurse's station, as the evaluation point, as in the second evaluation point 62 in Figure 1, it is possible to check whether the area is effectively isolated from the actual hospital room where the patient is staying by periodically operating the particle spray device 10 in the hospital room where the patient is staying. If a predetermined amount or more of fluorescent particles 40 are detected in the isolation area 200, it is possible to take measures such as issuing an alarm, indicating that there is a problem with isolation from the area 100.

The infection risk assessment method of the present invention can also be carried out in a test facility that simulates a hospital room, rather than in an actual hospital room, to study the behavior of droplet nuclei. In this case, conditions can be easily changed, such as the height or position of partitions, making it easy to assess infection risk under a variety of conditions.

In the embodiment shown in FIG. 1, the number of evaluation points is two, but it may be three or more or one.
Furthermore, the clean air cylinder 65 and the cleaning pipe 66 are not essential. If the evaluation point is one and the clean air cylinder 65 and the cleaning pipe 66 are not used, the sample changer 67 is not necessary.
Furthermore, the particle storage cartridge 20 is not limited to the one having the structure shown in FIG. 2, and for example, a cartridge described in Japanese Patent Application Laid-Open No. 2019-190914 may be used.

In the above embodiment, the operation for obtaining the data to be sent to the calculation device 80 is performed by a signal processing device built into the analysis device 70, but part or all of the signal processing may be performed by an external computer or the like connected by wire or wirelessly to the analysis device 70. Also, part or all of the signal processing may be performed by the calculation device 80.
In addition, various modifications are possible without departing from the spirit of the present invention.

The infection risk assessment method of the present invention was carried out in a simulated hospital room 110 shown in Figure 5. Beds 111, 112, 113, and 114 were placed in the simulated hospital room 110. In addition, a partition 115 was placed between beds 111 and 113, and a partition 116 was placed between beds 112 and 114.

The particle spray device 10 was placed at the patient's head position 101 on the bed 111. The patient's head position 101 was on the side of the bed 111 away from the bed 112.
The particle-containing cartridge used in the particle spray device 10 was the cartridge described in JP 2019-190914 A. The particle-containing cartridge was placed in the mouth of a thermal manikin (not shown). The temperature of the thermal manikin was set to 36°C.

The evaluation point 60 was set to the patient's head position 102 on the bed 112. The patient's head position 102 was set to the side of the bed 112 away from the bed 111.
A pipe (not shown) was provided from the evaluation point 60 to an analyzer (not shown) in a separate room so that gas could be sucked from the evaluation point 60. As the analyzer, a real-time bacteria detector (Instantaneous Microbial Detection ^™ ) manufactured by BioVigilant Systems was used.

The fluorescent particles used were lactose with riboflavin attached. The mass of riboflavin relative to the mass of lactose was 0.1%. The volume-based average particle diameter of the fluorescent particles as a whole was measured by a laser diffraction/scattering method and was found to be 5.4 μm.
300 mg of these fluorescent particles were loaded into the particle spraying device 10 and sprayed with an air flow under conditions of 0.4 MPa and 0.2 seconds.

The analysis results for the gas at evaluation point 60 are shown in Figure 6. As shown in Figure 6, the majority of particles were non-fluorescent particles (dust, etc. that are not fluorescent particles), but it was confirmed that the amount of fluorescent particles could be distinguished from dust, etc. and detected with high sensitivity.

10 Particle spray device 20 Particle storage cartridge 24 Spout 31 Compressor 33 Solenoid valve 40 Fluorescent particles 50 Thermal manikin 51 Mouth portion 60 Evaluation point 61 First evaluation point 62 Second evaluation point 63 First sampling tube 64 Second sampling tube 65 Clean air cylinder 66 Cleaning tube 67 Sample changer 70 Analysis device 71 Detection tube 72 Excitation light source 73 Fluorescence detection unit 74 Scattered light detection unit 80 Computing device 100 Simulated cough occurrence area 200 Isolation area

Claims (3)

a particle spray device that sprays fluorescent particles that emit fluorescence when irradiated with excitation light by simulating coughing or sneezing;
an analyzer for detecting the fluorescent particles;
a plurality of sampling pipes that suck gas from each of a plurality of evaluation points and supply the gas as a sample gas to the analysis device; and a cleaning pipe that supplies clean air to the analysis device;
the particle spray device includes a cylindrical cartridge with a bottom that contains the fluorescent particles;
the cartridge can be installed in the mouth of the thermal manikin, has a bottom serving as a storage location for the fluorescent particles, is provided with a lid having an outlet at its top, and has a gas introduction tube for blowing compressed air from above onto the fluorescent particles stored in the storage location, so that the blowing of compressed air from the gas introduction tube causes the fluorescent particles stored in the storage location to fly up and be sprayed to the outside through the outlet;
An infection risk assessment system in which the plurality of sampling tubes and the cleaning tube are switchably connected to the analytical device. The infection risk assessment system of claim 1, wherein the analysis device includes a detection tube through which the sample gas flows, an excitation light source that irradiates excitation light onto aerosol particles in the sample gas in the detection tube, and a fluorescence detection unit that detects fluorescence emitted from the aerosol particles in response to the excitation light. The infection risk assessment system of claim 2, wherein the analysis device further includes a scattered light detection unit that detects the excitation light scattered by the aerosol particles.