A close examination of COVID-19 spread

Interesting story at Science, about how a South African hospital was able to do a very careful trace of how COVID-19 spread through it:

On 9 March, a patient who had recently traveled to Europe and had symptoms of COVID-19 visited the emergency department of St Augustine’s, a private hospital in Durban, South Africa. Eight weeks later, 39 patients and 80 staff linked to the hospital had been infected, and 15 patients had died—fully half the death toll in KwaZulu-Natal province at that time.

Now, scientists at the University of KwaZulu-Natal have published a detailed reconstruction of how the virus spread from ward to ward and between patients, doctors, and nurses, based on floor maps of the hospital, analyses of staff and patient movements, and viral genomes. Their 37-page analysis, posted on the university’s website on 22 May, is the most extensive study of any hospital outbreak of COVID-19 so far. It suggests all of the cases originated from a single introduction, and that patients rarely infected other patients. Instead, the virus was mostly carried around the hospital by staff and on the surfaces of medical equipment.....

The report, which reads like a detective novel, tracks the virus’s spread through five hospital wards, including neurology, surgery, and intensive care units (ICUs), as well as to a nearby nursing home and dialysis center. Remarkably, no staff infections seem to have taken place in the hospital’s COVID-19 ICU, arguably the riskiest area of the hospital. That may be because patients are less infectious by the time they are admitted to intensive care, or because staff there are more diligent about preventing infection, the authors note.

The first patient, who sought help for coronavirus symptoms, only spent a few hours at the hospital, but likely transmitted the virus to an elderly patient admitted the same day for a stroke. The pair were in the hospital’s emergency department at the same time; the first patient was kept separate in a triage area, but that room was reached through the main resuscitation bay, where the stroke patient occupied a bed. (The emergency department was closed in April and opened again this month with an altered layout to improve infection control.) The two were also seen by the same medical officer.

The stroke patient, who developed a fever on 13 March, probably infected the first staff case, a nurse caring for her who developed symptoms on 17 March. A further four patients may have caught the virus from the stroke patient, including a 46-year-old woman admitted for severe asthma who had a bed opposite hers. Both she and the stroke patient died.

But on the whole, patients infected few other patients directly. Instead staff members spread the disease from patient to patient and from department to department—perhaps sometimes without becoming infected themselves. “We think in the main it’s likely to have been from [staff] hands and shared patient care items like thermometers, blood pressure cuffs, and stethoscopes,” says Richard Lessells, an infectious disease specialist at the KwaZulu-Natal Research Innovation and Sequencing Platform and one of the study leaders. He and the other authors found no evidence that aerosol transmission contributed to the outbreak.

 There is more at the link above.