Patterns of Virus Exposure and Presumed Household Transmission among Persons With Coronavirus Disease, United States, January–April 2020

Rachel M. Burke; Laura Calderwood; Marie E. Killerby; Candace E. Ashworth; Abby L. Berns; Skyler Brennan; Jonathan M. Bressler; Laurel Harduar Morano; Nathaniel M. Lewis; Tiff anie M. Markus; Suzanne M. Newton; Jennifer S. Read; Tamara Rissman; Joanne Taylor; Jacqueline E. Tate; Claire M. Midgley

Disclosures

Emerging Infectious Diseases. 2021;27(9):2323-2332.

Abstract and Introduction

Abstract

We characterized common exposures reported by a convenience sample of 202 US patients with coronavirus disease during January–April 2020 and identified factors associated with presumed household transmission. The most commonly reported settings of known exposure were households and healthcare facilities; among case-patients who had known contact with a confirmed case-patient compared with those who did not, healthcare occupations were more common. Among case-patients without known contact, use of public transportation was more common. Within the household, presumed transmission was highest from older (≥65 years) index case-patients and from children to parents, independent of index case-patient age. These findings may inform guidance for limiting transmission and emphasize the value of testing to identify community-acquired infections.

Introduction

Coronavirus disease (COVID-19) was first identified in Wuhan, China, in December 2019.^[1] The first reported case in the United States was identified in January 2020;^[2] by mid-March, cases had been reported in all 50 states.^[3] On March 16, 2020, the White House Coronavirus Task Force published guidance for curbing community spread of COVID-19;^[4] soon after, states began to enact stay-at-home orders.^[5] By late May 2020, all 50 states had begun easing restrictions; reported cases reached new peaks in the summer and then winter months of 2020.^[6,7] As restrictions further ease with increased availability of vaccine, and as pandemic fatigue may cause persons to adhere less consistently to recommended guidance such as masking and distancing, it may be informative to look back at exposures and within-household transmission during a period when few mitigation measures were in place. We characterized exposures common among persons with the earliest reported confirmed COVID-19 cases in the United States (onset mid-January through early April 2020) and identified factors associated with presumed household transmission.

This activity was reviewed by the Centers for Disease Control and Prevention (CDC) and was conducted consistent with applicable federal law and CDC policy. Forms were approved under the Office of Management and Budget (no. 0920–1011).

1 2 3 4

Next Section

Abstract and Introduction
Methods
Results
Discussion
References

Table 1. Reported exposures of 179 COVID-19 case-patients with submitted case investigation forms by known contact with a laboratory-confirmed COVID-19 case-patient, United States, January–April 2020*
Exposure	No known contact, no. (%), n = 97	Known contact, no. (%), n = 82	p value†
Workplace setting‡			0.10
Accommodation, food, and other services§	9 (10.0)	2 (2.8)
Construction	4 (4.4)	1 (1.4)
Education¶	9 (10.0)	5 (6.9)
Healthcare	10 (11.1)	20 (27.8)
Manufacturing	2 (2.2)	1 (1.4)
Professional or office setting	10 (11.1)	7 (9.7)
Transportation and warehousing and utilities	8 (8.9)	3 (4.2)
Wholesale or retail trade	3 (3.3)	7 (9.7)
Other	7 (7.8)	6 (8.3)
Insufficient information	5 (5.6)	6 (8.3)
Not currently in the workforce	23 (25.6)	14 (19.4)
Other exposure risks in previous 14 d
Spent time in a healthcare setting			0.0044
Yes	24 (26.1)	39 (48.1)
No	68 (73.9)	42 (51.9)
Close contact with a contact of a confirmed case			0.0002
Yes	3 (3.6)	17 (25.4)
No	81 (96.4)	50 (74.6)
Attended a mass gathering**			0.07
Yes	29 (35.8)	16 (21.3)
No	52 (64.2)	59 (78.7)
Used public transportation			0.0048
Yes	23 (44.2)	8 (16.3)
No	29 (55.8)	41 (83.7)
Attended or worked at a school or daycare			1.00
Yes	8 (14.3)	7 (14.3)
No	48 (85.7)	42 (85.7)
Had a household member who attended school or daycare			0.51
Yes	15 (18.3)	9 (13.0)
No	67 (81.7)	60 (87.0)
Travel away from home			0.14
International, with or without domestic	18 (18.9)	8 (10.0)
Domestic only	18 (18.9)	13 (16.3)
None	59 (62.1)	59 (73.8)

*A total of 23 persons did not know or did not report whether they had known contact with a person with laboratory-confirmed COVID-19 in the 14 d before their own illness onset. Denominators differ because some questions had incomplete responses. All complete responses are presented for each question. COVID-19, coronavirus disease.
†χ² or Fisher exact test.
‡Based on 2012 census industry codes. Mapping shown in Appendix 2 (https://wwwnc.cdc.gov/EID/article/27/9/20-4577-App2.pdf).
§Not including public administration services.
¶Includes persons ≥18 y of age who are pursuing higher education.
**Examples given in the questionnaire included religious event, wedding, party, dance, concert, banquet, festival, sports event, or other event.

Table 2. Factors associated with symptom status of 172 household contacts of 64 symptomatic index case-patients in households with presumed COVID-19 transmission, United States, January–April 2020*
Factor	Unique households	No. with symptoms/no. total contacts (%)	aOR (95% CI)†	p value‡
Contact sex				0.73
F	50	28/85 (32.9)	Referent
M	46	29/87 (33.3)	0.90 (0.49–1.64)
Contact age, y				0.73
<18	25	13/50 (26.0)	Referent
≥18	63	44/115 (38.3)	1.15 (0.53–2.47)
Household size, persons				0.006
<5	48	23/92 (25.0)	Referent
≥5	16	34/80 (42.5)	3.56 (1.45–8.74)
Index case-patient age, y				0.035
<5	5	11/19 (57.9)	3.69 (0.65–20.95)
5–17	4	6/13 (46.2)	2.09 (0.39–11.05)
18–44	26	15/82 (18.3)	Referent
45–64	21	20/49 (40.8)	4.61 (1.45–14.66)
≥65	8	5/9 (55.6)	15.43 (2.28–104.17)
Relationship of contact to index case-patient				0.070
Spouse	43	11/44 (25.0)	Referent
Child	21	11/39 (28.2)	1.78 (0.58–5.45)
Parent	17	18/31 (58.1)	4.55 (1.22–17.00)
Other§	23	17/58 (29.3)	1.47 (0.42–5.11)

*A total of 21 contacts from 5 households (i.e., 5 index case-patients) are excluded because of missing data: only relationship data for 7, only sex data for 2, only index case-patient's age for 1; only contact's age for 5, relationship and contact age for 6. Households with presumed transmission indicates households of laboratory-confirmed COVID-19 case-patients where >1 household member exhibited symptoms; index case-patient indicates household/member with first reported onset of symptoms (regardless of laboratory confirmation); household contact indicates household member of the index case-patient. aOR, adjusted odds ratio (adjusted for all variables in the table); COVID-19, coronavirus disease.
†Calculated using robust SEs.
‡Generalized Wald test.
§Includes siblings, grandparents, grandchildren, friends, and any household relationship or contact other than spouse, child, or parent.