Testing results

On 9 March 2020, The Director of Public Health, Dr Nicola Brink, announced the first positive case of COVID-19, in the island. See the following media release for more details.

The positive results are a result of infections acquired in UK, France, Tenerife, Mainland Spain, Germany, Austria, Switzerland, Jersey and Guernsey.

There are currently 6 patients being managed within the PEH with COVID-19. No patients are currently requiring intensive care support.

Nine confirmed COVID-19 deaths – COVID-19 positive on laboratory testing / throat swab. 

Four presumptive COVID-19 deaths – no laboratory testing or negative laboratory testing, but cause of death thought to be COVID-19 related.

On 13th April, an analysis of the 219 confirmed cases showed that:

• 62% of cases were among females; 38% among males;
• Infections have been recorded in individuals aged from 0 to 99;
• 96% of infections have been in adults aged 18 and over; 4% have been among children under age 18.

We are defining recovery as having no virus detectable on their nose/throat swab on Day 14.

97 people with proven COVID-19 have been confirmed to have recovered from COVID-19 and have no virus detectable on their nose/throat swab. 

To monitor the trajectory of infections in the Bailiwick, Public Health Services monitor positive test results. Each positive test result is plotted against the day that symptoms began (or against testing date if no symptom-onset date is available).

We are assuming that for each positive test result, that there may be 1.4 actual cases of coronavirus on the Island. This assumption is based on research which suggests that around 40% of infected individuals may be asymptomatic.  In other words we assume that we are detecting all symptomatic cases but missing another 40% who are asymptomatic; this represents the expected proportion of asymptomatic / mild cases that are not recognised as cases. This is then used to estimate the new number of new actual cases each day. Using this information the trajectory of the increase of coronavirus cases can be plotted for the Bailiwick. A 5-day moving average is used to adjust for random fluctuation in daily cases and make the curve smoother and easier to analyse.

What the graph below shows is that, even allowing for some undercounting, our cases numbers (blue line) have not risen exponentially as one would expect in a model mitigated by social distancing (orange line) alone. The grey dotted line shows what would have happened if there had been no mitigation.  So, what this shows is that our case numbers are currently stable.  We have so far succeeded in flattening the curves we might otherwise have seen had we not put our actions in place to prevent the on-going transmission of the virus in our community.

The graph below indicates trends on a logarithmic scale. On this scale, a straight diagonal upward line indicates exponential growth rate. Here the projected number of cases doubling in two, three and five days is illustrated with the grey dashed lines.  This illustrates that the rate of spread in the Bailiwick is starting to decline.

The figure below illustrates the number of contact identified per case before and after lockdown was introduced. The lag observed in the number of contacts per case aligns with the average incubation period from the time of infection to the development of symptoms of COVID-19.