Viable Influenza A Virus in Airborne Particles from Human Coughs

Figures & data

FIGURE 1 Cough aerosol particle collection system. Before each cough, the piston spirometer was purged and partially filled with 4 L of dry filtered air. When the patient coughed into the mouthpiece, the cough flowed through an ultrasonic spirometer which measured the cough volume and flow rate. The cough then flowed through a valve and into the piston spirometer, displacing the piston to the right. The droplet tray collected any large drops that impacted it. When the subject finished coughing, the valve was closed and the SKC BioSampler was turned on. The cough aerosol was pulled out of the spirometer and collected by the aerosol sampler. Airborne droplets larger than about 10–15 μm collected in the sampler elbow, while smaller particles were collected in the sampler collection media. As the aerosol sampler drew air, the piston moved to the left until no air remained in the spirometer.

Table I Demographic and Medical Information for Study Participants Who Were Influenza-Positive

Influenza A detected in cough aerosol particles?	Yes		No
# of subjects	7		10
Gender	5 male, 2 female		7 male, 3 female
	Mean	SD	Mean	SD
Age (years)	19	1.2	23	5.9
Height (cm)	172	10	177	12
Weight (kg)	74	21	86	28
Temperature (°C)	37.9	0.84	37.4	0.47
# of days of symptoms	2.0	2.0	1.9	0.9
Volume of each cough (liters)	2.3	0.5	2.3	1.2
Peak flow rate during coughs (liters/second)	6.9	1.5	6.9	2.9
Number of subjects reporting:
Fever/chills	7		10
Headache	6		8
Fatigue	6		8
Cough	7		9
Sore throat	3		7
Sinus congestion	3		3
Runny nose	6		9
Sneezing	3		6
Muscle aches	5		9
Received influenza vaccine within last 6 months	0		1

Notes: A subject was considered influenza-positive if at least one of their samples (swab, sampler elbow, or tray) produced both a positive VPA and a positive VRA. Information for all of the patients is included in the online supplemental information.

Table II Viral Plaque Assay (VPA) and Viral Replication Assay (VRA) Results for Influenza-Positive Test Subjects

			Naso- and Oropharyngeal Swabs		Aerosol Sampler Media		Sampler Elbow		Droplet Tray
		Subject	VPA	VRA	VPA	VRA	VPA	VRA	VPA	VRA
	Year	#	(PFU)	(# of copies)	(PFU)	(# of copies)	(PFU)	(# of copies)	(PFU)	(# of copies)
		FC76	3.38 × 10^5	2.41 × 10^7	0	0	0	0	0	0
		FC80	2.13 × 10^5	1.17 × 10^8	0	0	0	0	0	0
	2011	FC81	1.21 × 10^5	1.47 × 10^8	0	0	0	0	0	0
		FC82	9.00 × 10^5	1.66 × 10^8	0	0	4	0	0	0
Subjects with viable influenza A in swab samples but with no viable virus in cough aerosol		FC97	2.11 × 10^4	8.01 × 10^6	0	0	0	0	0	0
		FC102	2.63 × 10^4	5.93 × 10^6	0	0	0	n/t	0	n/t
		FC105	114	9.62 × 10^4	0	0	0	n/t	0	n/t
	2014	FC106	6.86 × 10^4	2.85 × 10^7	0	674	0	n/t	0	n/t
		FC113	8.03 × 10^4	3.09 × 10^7	5	0	0	n/t	0	n/t
		FC121	8.10 × 10^3	2.67 × 10^6	0	0	0	n/t	0	n/t
		FC84	25	8.16 × 10^7	6	2.91 × 10^6	0	0	0	0
	2011	FC88	n/a	n/a	356	1.99 × 10^6	0	2.85 × 10^5	0	0
		FC95	5.13 × 10^4	5.52 × 10^10	538	4.40 × 10^8	26	1.76 × 10^6	6	1.47 × 10^6
Subjects with viable influenza A virus in cough aerosol
		FC100	6	0	5	1.49 × 10^3	0	n/t	0	n/t
	2014	FC104	2.55 × 10^6	2.92 × 10^8	25	1.30 × 10^4	0	n/t	0	n/t
		FC109	3.90 × 10^7	4.40 × 10^7	50	1.26 × 10^4	0	n/t	0	n/t
		FC123	7.73 × 10^4	1.61 × 10^7	13	4.14 × 10^3	0	n/t	0	n/t

Notes: For the aerosol sampler collection media, sampler elbow, and droplet tray, the results are the totals found from six voluntary coughs collected over about 20 min. N/a indicates that swabs were not collected from that patient. N/t indicates that a VRA was not performed. The results for all of the patients are included in the online supplemental information.