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.

The samples tested number relates to all the sampling and testing activity associated with finding out if a person is positive or negative during ‘one testing episode’

For example - a person who is symptomatic, is swabbed and the test outcome is positive.  One is added to ‘samples tested’ and one to ‘positive results’.  After two weeks the case is re-swabbed to see if they have cleared their infection.  They are negative and deemed recovered.  Neither the extra swab nor the new negative result are counted as this relates to the original testing episode which has already registered on our statistics.

Three patients are currently in-patients with confirmed COVID-19.

No patients are currently receiving intensive care support.

11 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.

Details of deaths registered in Guernsey between 1 January 2010 and 18 April 2020 have been examined by the Health Intelligence Unit, Public Health Services, to determine the impact of the COVID-19 pandemic on local death registrations from COVID-19 and other causes. The full report can be found in the downloads section on this page.

On 20th April, an analysis of the 239 confirmed cases showed that:

• 63% of cases were among females; 37% 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 or later if a person is still symptomatic on Day 14.

On 20th April, an analysis of the 239 confirmed cases showed that:

• 63% of cases were among females; 37% 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.

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 1.67 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. This figure was updated on the 21st April 2020.