Isolation and quarantine for COVID-19 in the United States, 2020-2022.

BACKGROUND: Public health programs varied in ability to reach people with COVID-19 and their contacts to encourage separation from others. For both adult cases of COVID-19 and contacts, we estimated the impact of contact tracing activities on separation behaviors from January, 2020 until March, 2022. METHODS: We used a probability-based panel survey of a nationally representative sample to gather data for estimates and comparisons. RESULTS: An estimated 64,255,351 adults reported a positive SARS-CoV-2 test result; 79.6% isolated for >5 days, 60.2% isolated for >10 days, and 79.2% self-notified contacts. 24,057,139 (37.7%) completed a case investigation and 46.2% reported contacts to health officials. More adults who completed a case investigation isolated than adults who did not (>5 days, 82.6%; >10 days, 69.8% versus >5 days, 78.2% and >10 days 54.8%; p-values for both measures <0.05).84,946,636 adults were a contact to a COVID-19 case; 73.1% learned of their exposure directly from a case; 49.4% quarantined for >5 days, 18.7% quarantined for >14 days, and 13.5% completed a contact tracing call. More who completed a contact tracing call quarantined than those who did not (>5 days, 61.2%; >14 days, 25.2% versus >5 days, 48.5%; >14 days, 18.0%; p-values for both measures <0.05). CONCLUSIONS: Engagement in contact tracing positively correlated with isolation and quarantine. However, most adults with COVID-19 isolated and self-notified contacts regardless of whether the public health workforce was able to reach them. Identifying and reaching contacts was challenging, and limited the ability to promote quarantining, and testing.

Social contact patterns among employees in 3 U.S. companies during early phases of the COVID-19 pandemic, April to June 2020.

We measured contact patterns using online diaries for 304 employees of 3 U.S. companies working remotely. The median number of daily contacts was 2 (IQR 1-4); majority were conversation (55 %), occurred at home (64 %) and lasted >4 h (38 %). These data are crucial for modeling outbreak control among the workforces.

Measuring voluntary and policy-induced social distancing behavior during the COVID-19 pandemic.

Staying home and avoiding unnecessary contact is an important part of the effort to contain COVID-19 and limit deaths. Every state in the United States enacted policies to encourage distancing and some mandated staying home. Understanding how these policies interact with individuals' voluntary responses to the COVID-19 epidemic is a critical initial step in understanding the role of these nonpharmaceutical interventions in transmission dynamics and assessing policy impacts. We use variation in policy responses along with smart device data that measures the amount of time Americans stayed home to disentangle the extent that observed shifts in staying home behavior are induced by policy. We find evidence that stay-at-home orders and voluntary response to locally reported COVID-19 cases and deaths led to behavioral change. For the median county, which implemented a stay-at-home order with about two cases, we find that the response to stay-at-home orders increased time at home as if the county had experienced 29 additional local cases. However, the relative effect of stay-at-home orders was much greater in select counties. On the one hand, the mandate can be viewed as displacing a voluntary response to this rise in cases. On the other hand, policy accelerated the response, which likely helped reduce spread in the early phase of the pandemic. It is important to be able to attribute the relative role of self-interested behavior or policy mandates to understand the limits and opportunities for relying on voluntary behavior as opposed to imposing stay-at-home orders.

Influenza-negative influenza-like illness (fnILI) Z-score as a proxy for incidence and mortality of COVID-19.

Although direct detection of SARS-CoV2 in symptomatic or asymptomatic individuals is the ideal epidemiological tool for determining the burden of disease, the lack of availability of testing can preclude its wider implementation as a robust surveillance system. We correlated the use of the derivative influenza-negative influenza-like illness (fnILI) z-score from the US Centers for Disease Control and Prevention as a proxy for incident cases and disease-specific deaths. For every unit increase of fnILI z-score, the number of cases increased by 376.5 (95% CI [202.5, 550.5]) and number of deaths increased by 10.2 (95% CI [5.4, 15.0]). FnILI data may serve as an accurate outcome measurement to track the spread of COVID-19 infection and disease, and allow for informed and timely decision-making on public health interventions.