FRIDAY, May 1, 2020 (HealthDay News) — Contact tracing can reduce the time to case isolation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), according to a study published online April 27 in The Lancet Infectious Diseases.

Qifang Bi, from Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, and colleagues compared cases identified through symptomatic surveillance and contact tracing using data from 391 SARS-CoV-2 cases and 1,286 close contacts identified from Jan. 14 to Feb. 12, 2020. The time from symptom onset to confirmation, isolation, and admission to hospital was estimated.

The researchers found that 91 percent of 391 cases had mild or moderate clinical severity at initial assessment. Three cases had died and 225 had recovered as of Feb. 22, 2020 (median time to recovery, 21 days). On average, cases were isolated 4.6 days after symptom development; this was reduced by 1.9 days with contact tracing. The risk for infection was higher for household contacts and those traveling with a case (odds ratios, 6.27 and 7.06, respectively) compared with other close contacts. There was an 11.2 percent household secondary attack rate; children were as likely to be infected as adults (infection rate, 7.4 and 6.6 percent for children <10 years and population average, respectively). The observed reproduction number was 0.4, with a 6.3-day mean serial interval.

“As SARS-CoV-2 continues to spread, it is important that we continue to expand our knowledge about its transmission and natural history,” the authors write.

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