Understanding the Spread of COVID-19 in the United States

Initial Cases and Transmission

Declared a pandemic by the World Health Organization (WHO), the Coronavirus disease 2019 (COVID-19) is spreading rapidly, prompting researchers to quickly analyze its transmission patterns. Recent research published in The Lancet highlights the first known instance of person-to-person transmission of COVID-19 in the United States. The first confirmed case in Illinois involved a woman returning home from Wuhan, China, in mid-January, followed by her husband as the second confirmed case. Initial symptoms included mild fever, fatigue, and cough. The woman was hospitalized for pneumonia and later tested positive for COVID-19. Eight days following her diagnosis, her husband was also hospitalized due to coughing up blood and shortness of breath, ultimately receiving a COVID-19 diagnosis.

Investigation and Contact Tracing

In response, various Illinois state health departments coordinated with the US Centers for Disease Control and Prevention (CDC) for technical support and onsite investigations. The locations visited by the infected couple were thoroughly examined, and crucial records such as staffing and patient logs, as well as security footage, were reviewed to identify additional individuals who may have been exposed to the virus. In total, 372 potential contacts were identified.

Out of these contacts, 347 individuals were assessed, classified by risk, and actively monitored for 14 days following their last exposure to a COVID-19 patient. The exposure classifications adhered to criteria established by the CDC and the COVID-19 investigation team. Active symptom monitoring was conducted electronically, with contacts receiving bi-daily emails asking about their symptoms and self-measured temperatures. If any indicative symptoms were reported, or if a contact failed to respond, a public health official would follow up via phone. Specimens were also collected and sent to the CDC for testing.

Findings and Implications

At the conclusion of the study period, no further cases of COVID-19 were identified through the active symptom monitoring process. Based on the transmission from the index patient to her husband and the data collected, researchers believe that person-to-person transmission likely occurs through unprotected and prolonged exposure to symptomatic individuals.

The researchers suggest that factors including the severity of illness, the extent of viral shedding, and the timing of exposure to symptomatic patients can significantly influence virus transmission. However, they caution that the data is preliminary, as only one transmission event was studied. Additionally, not all individuals potentially exposed to COVID-19 may have been identified due to reliance on the couple’s memory and the standardized questionnaires used.

Future Directions for Public Health

The study took place prior to the CDC’s updated guidance recommendations for screening, meaning that active symptom monitoring may not have detected asymptomatic transmissions. While vaccines are still under development, studies like this one can provide valuable insights for public health recommendations. They can inform protocols regarding the type and duration of isolation for infected patients and improve contact tracing strategies for potential cases.

Written by Stephanie Tsang

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References

Isaac Ghinai, Tristan D McPherson, Jennifer C Hunter, Hannah L Kirking, Demian Christiansen, Kiran Joshi, Rachel Rubin, Shirley Morales-Estrada, Stephanie R Black, Massimo Pacilli, Marielle J Fricchione, Rashmi K Chugh, Kelly A Walblay, N Seema Ahmed, William C Stoecker, Nausheen F Hasan, Deborah P Burdsall, Heather E Reese, Megan Wallace, Chen Wang, Darcie Moeller, Jacqueline Korpics, Shannon A Novosad, Isaac Benowitz, Max W Jacobs, Vishal S Dasari, Megan T Patel, Judy Kauerauf, E Matt Charles, Ngozi O Ezike, Victoria Chu, Claire M Midgley, Melissa A Rolfes, Susan I Gerber, Xiaoyan Lu, Stephen Lindstrom, Jennifer R Verani, Jennifer E Layden. First known person-to-person transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the USA. The Lancet, 2020; DOI: 10.1016/S0140-6736(20)30607-3

“The Lancet: Study Details First Known Person-to-Person Transmission of New Coronavirus in the USA.” EurekAlert!, 12 Mar. 2020, www.eurekalert.org/pub_releases/2020-03/tl-pss031220.php. Image by mattthewafflecat from Pixabay.