1 in 4 coronavirus patients in US didn't know how they got infected, suggesting community spread: CDC

Case investigation, contact tracing, isolation of infected persons as well as social distancing and more widespread use of cloth face coverings are warranted, says the agency


                            1 in 4 coronavirus patients in US didn't know how they got infected, suggesting community spread: CDC
(Getty Images)

More than half of the coronavirus patients in the US could not identify how they got infected in a survey, which suggests that several might be getting the infection through transmission in their communities and not from a close contact in their lives. The analysis by the US Centers for Disease Control and Prevention (CDC) comes as cases continue to soar across the US. The frequent lack of a known contact, as seen in 54% of the patients in the current analysis, underscores the need for isolation of infected persons, contact tracing and testing during ongoing community transmission, as well as prevention measures such as social distancing and use of cloth face coverings in public, says the research team.

Reports documenting exposures to SARS-CoV-2, the virus that causes Covid-19, have generally been described within congregate settings, such as meat and poultry processing plants and long-term care facilities, rather than broader community settings. According to the CDC, understanding individual behaviors and demographic characteristics of patients with Covid-19 and risks for severe illness requiring hospitalization can inform efforts to reduce transmission.

The analysis is based on telephone interviews of 350 coronavirus patients, both outpatient and inpatient, from 11 US academic medical centers in nine states. The interviews were conducted during April 15-May 24 with a random sample of adults over 18 years, who had tested positive for Covid-19. Respondents were contacted 14-21 days after Covid-19 testing and asked about their demographic characteristics, underlying chronic conditions, symptoms experienced on the date of testing, and potential exposures to SARS-CoV-2 during the two weeks before illness onset, or the date of testing among those who did not report symptoms at the time of testing.

According to the CDC, understanding individual behaviors and demographic characteristics of patients with Covid-19 and risks for severe illness requiring hospitalization can inform efforts to reduce transmission. (Getty Images)

Among 350 interviewed patients, 271 or 77% were outpatients and 79 or 23% were inpatients. “Compared with outpatients, inpatients were older (median age 54 versus 42 years). Inpatients were less likely to be white (19% versus 37%) and more likely to have an annual household income of less than $25,000 (28% versus 13%). Inpatients also had more underlying medical conditions, including cardiovascular conditions, chronic respiratory disease and diabetes. Fewer inpatients (39%, 20 of 51) reported a return to a baseline level of health at 14-21 days than did outpatients (64%, 150 of 233),” write authors.

Self-reported characteristics of outpatients and inpatients. (CDC)

The research team found that one in four Covid-19 patients could not identify a person with whom they had close contact in the last two weeks. Among 339 (97%) participants who provided exposure histories, approximately one half (46%, 153 of 332) of patients reported known close contact — defined as being within six feet of someone with a diagnosis of Covid-19 — during the two weeks preceding illness onset or the date of testing for asymptomatic patients. This was most commonly a family member (45%, 69 of 153) or a work colleague (34%, 52 of 153). Approximately two-thirds (64%, 212 of 333) of participants were employed, but only 35 of 209 (17%) were able to telework. Seven of the 339 participants were missing data in their case contact histories.

Outpatients were more likely to report being employed than were inpatients (70% versus 42%) and interacted with persons outside the home more frequently. Among employed participants, 53 (25%) reported working in healthcare.

Based on their findings, the CDC recommends limiting close contact with people who do not live in the same house, wearing face-covering in public, and washing hands frequently. “Fewer than one-half of patients were aware of recent close contact with someone with Covid-19, highlighting a need for increased screening, case investigation, contact tracing, and isolation of infected persons to prevent ongoing community transmission. This finding suggests that ensuring social distancing and more widespread use of cloth face coverings are warranted. A majority of Covid-19 patients reported working during the two weeks preceding illness, and few had the ability to telework, underscoring the need for enhanced measures to ensure workplace safety,” says the team.

Over 2,634,430 coronavirus cases have been reported from across the US as of July 1, and more than 127,400 have died in the Covid-19 pandemic.

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