The first 2 months of COVID-19 contact tracing in the Northern Territory of Australia, March–April 2020

Abstract

<jats:p>The Northern Territory (NT) Centre for Disease Control (CDC) undertook contact tracing of all notified cases of coronavirus disease 2019 (COVID-19) within the Territory. There were 28 cases of COVID-19 notified in the NT between 1 March and 30 April 2020. In total 527 people were identified as close contacts over the same period; 493 were successfully contacted; 445 were located in the NT and were subsequently quarantined and monitored for disease symptoms daily for 14 days after contact with a confirmed COVID-19 case. Of these 445 close contacts, 4 tested positive for COVID-19 after developing symptoms; 2/46 contacts who were cruise ship passengers (4.3%, 95% CI 0.5–14.8%) and 2/51 household contacts (3.9%, 95% CI 0.5–13.5%). None of the 326 aircraft passengers or 4 healthcare workers who were being monitored in the NT as close contacts became cases.</jats:p>

Household transmission of SARS-CoV-2: a systematic review and meta-analysis of secondary attack rate

“…After a household member is confirmed to be infected with SARS-CoV-2, household or family contacts are identified, followed for a short duration of time (e.g., two weeks), and tested if eligible for testing according to national testing guidelines to ascertain secondary infections. Index cases were identified by passive surveillance, 21 , 28 , 29 , 31 , 38 – 40 , 43 , 44 , 49 – 51 active surveillance of key populations (e.g., travelers from areas with active SARS-CoV-2 transmission, and individuals detected by neighborhood fever screenings), 25 , 27 , 34 both active and passive surveillance, 14 , 15 , 17 – 20 , 22 , 24 , 26 , 30 , 32 , 33 , 35 , 36 , 41 , 46 , 48 , 52 , 53 or regional seroprevalence surveys. 42 , 45 We did not include case reports or cluster investigations that focused on individual households or families in an effort to reduce publication bias.…”

“…Many studies only included household contacts, 14 , 26 , 28 , 29 , 31 , 35 , 37 , 38 , 40 , 41 , 43 , 49 , 50 , 53 but others included family members, 15 , 20 , 21 , 23 , 27 , 30 or other close contacts, 16 – 19 , 22 , 24 , 25 , 32 – 34 , 36 , 39 , 42 , 44 , 46 – 48 , 52 including individuals outside the household. Of the latter studies of close contacts, many reported SARs among household contacts, 17 , 18 , 22 , 24 , 25 , 32 – 34 , 36 , 39 , 42 , 44 , 46 – 48 , 52 or all family members. 16 , 19 – 21 , 23 , 27 , 30 We did not include studies of close contacts that did not report SARs for household or family members.…”

“…Most studies involved tracing contacts and monitoring them for 14, 14 , 16 – 18 , 22 , 24 , 28 – 34 , 37 – 39 , 44 , 47 , 48 , 50 , 52 or 21 days. 19 , 26 Monitoring methods included phone calls, 21 , 34 , 39 , 44 text messages, 39 , 44 or direct observation by healthcare workers. 17 , 33 Some studies tested all contacts immediately after the index case was diagnosed at the onset of the observation period and monitored them for symptoms.…”

“…Many studies, particularly those in China, reported in-home quarantine of contacts during the observation period after index cases were confirmed. 14 , 17 – 19 , 22 , 24 , 29 – 34 , 36 , 37 , 44 , 46 , 47 , 50 – 52 …”

“…Case ascertainment was primarily done via RT-PCR on nasopharyngeal or oropharyngeal samples. 14 , 17 , 18 , 21 – 23 , 26 – 33 , 35 – 37 , 40 , 44 , 46 – 53 However, several studies also reported whole-genome sequencing, 27 , 28 , 32 , 47 nucleic acid tests, 19 , 25 , 27 and antibody tests. 42 , 45 Two studies identified index cases via RT-PCR, but only collected symptom information about household contacts from telephone interviews with index cases.…”