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Hotspot Purpose, Measures, and Scoring Criteria

Purpose

This dashboard was designed for internal use by PERC partners to identify countries that have growing or widespread outbreaks of COVID-19. This dashboard was intentionally designed to be highly sensitive at the cost of specificity, meaning that countries may be assigned high hotspot levels at time when transmission in the country is low. PERC partners use this dashboard to identify countries where a deeper dive into that country’s data and outbreak status is warranted and where technical support around COVID-19 may be beneficial. Hotspot levels are assigned based on the numbers of cases and tests each country reports, and hotspot levels may be assigned too low if a country is not testing, identifying, and reporting their COVID-19 cases.

What is each measure?

Test-Case Ratio Adjusted Incidence (Cases/1 million population/week)

This indicator estimates the incidence rate for each country if they were conducting enough testing to achieve a test-case ratio of ≥20 (equivalent to 5% test positivity). Incidence is linearly scaled upward until a test-case ratio of 20 is achieved. For example, a country with a test-case ratio of 10 would have their incidence doubled to account for its low testing rate. For countries with a test-case ratio ≥20, no adjustment is made.

If a country reported no testing data over the prior 2 weeks, or if it reported more cases than tests over the prior 2 weeks, the warning level for this indicator is automatically increased one level above the level corresponding to that country’s unadjusted incidence rate. For example, if a country has an unadjusted incidence rate of 50 cases/1M/week that corresponds to warning level 2, but that country has not reported testing data, that country would be assigned warning level 3 for this indicator.

Incidence is calculated per week, and an average for the most recent two weeks is used to calculate the test-case ratio.

Equations:

If test per case ratio ≥20:

\[{[New {cases \over week} *1\ Mil.] \over population}\]

If test per case ratio <20 and ≥1:

\[ \frac{[New {cases \over week} *1\ Mil.]}{population} * \frac{[20\ tests\ per\ case\ (Target)]}{[Tests\ per\ case\ (2\ week\ avg.)]} \]

If test per case ratio <1 or no tests reported in prior two weeks, and then automatically increase warning level by 1:

\[ \frac{[New {cases \over week} *1\ Mil.]} {population} \]

Trend in Incidence Rate

This indicator calculates the percent change in the number of new cases across weeks, to determine if the incidence of COVID-19 is trending upwards or downwards.

Equations:

Increase for the latest week:

\[ \frac{[New\ cases\ most\ recent\ week]-[New\ cases\ 1\ week\ prior]} {[New\ cases\ 1\ week\ prior]} \]

Increase from latest week to two weeks prior:

\[ \frac{[New\ cases\ most\ recent\ week]-[New\ cases\ 2\ weeks\ prior]} {[New\ cases\ 2\ weeks\ prior]} \]

Increase in two consecutive weeks:

\[ \frac{[New\ cases\ most\ recent\ week]-[New\ cases\ 1\ week\ prior]} {[New\ cases\ 1\ week\ prior]} \]

AND

\[ \frac{[New\ cases\ 1\ week\ prior]-[New\ cases\ 2\ weeks\ prior]} {[New\ cases\ 2\ weeks\ prior]} \]

Test positivity

This indicator calculates the proportion of individuals that received a COVID-19 test in the prior 2 week who tested positive. As COVID-19 infections in a country increase, the test positivity should increase, making this a useful indicator for identifying countries with a growing outbreak. This indicator is especially useful in countries with limited testing capacity, since those countries may report a low COVID-19 incidence rate during a surge because they fail to test and diagnose most cases. Yet, in scenarios where national testing coverage is low, test positivity should still increase when a country experiences a surge of cases.

Equation:

Test positivity (last 14 days):

\[{[New\ cases\ most\ recent\ 2\ weeks] \over [Tests\ conducted\ most\ recent\ 2\ weeks]}\]

COVID-19 testing includes both PCR and antigen tests, consistent with the WHO case definition and Africa CDC guidelines. In addition, if a country has reported no testing data in any of the previous three weeks, the country is assigned warning level 0 because test positivity cannot be accurately assessed when test counts are not routinely reported.

How is each measure scored?

Indicator Test-case ratio adjusted incidence Level 1: Lower Risk <35 cases/1M/week Level 2: Medium Risk 35 to <150 cases/1M/week Level 3: High Risk 150 to <1000 cases/1M/week Level 4: Very High Risk ≥1000 cases/1M/week
Indicator Trend in incidence rate Level 1: Lower Risk <20% increase in the latest week AND <30% increase from the latest week to two weeks prior OR <75 cases over the prior 3 weeks Level 2: Medium Risk >20% increase in the latest week OR an increase from 0 to ≥1 case in the latest week OR >30% increase from the latest week to two weeks prior Level 3: High Risk >40% increase in the last week OR >15% increase in two consecutive weeks Level 4: Very High Risk ≥25% increase in two consecutive weeks OR >0% increase in three consecutive weeks
Test positivity (last 14 days) <3% 3% - <5% 5% - <12% ≥12%

How is the overall hotspot warning level determined?

The overall hotspot warning level of a county is determined by calculating the mean of the three indicators, excluding any indicators assigned level 0 because of missing data. The mean of these indicators is rounded up to increase the sensitivity of the dashboard (e.g. if the mean of the three indicators is 2.3, an overall level of 3 is assigned). This is done to ensure that the system identifies countries as soon as data suggests that there may be a growing outbreak. This system was not designed to identify which countries have the worst outbreak or highest incidence. Rather, the objective is to highlight countries that should receive attention either due to an increasing or widespread outbreak.

What is our data source?

Africa CDC receives cases, deaths and testing data from each African Union Member State. The data is updated twice a day, at 9am and 5pm EAT. It is not uncommon for countries to report data several days late, and totals for past days will be updated as additional data is reported to Africa CDC. The most recent date that each country reported a case to Africa CDC is indicated on the “Most recent epi data” column on the front page of the dashboard. Additionally, some countries may report cases and deaths, but not testing data, and some countries report testing data in periodic batches (eg. weekly) rather than providing daily statics.

Information on other key measures

Trend measures (New Case, Death and Test Trends)

All trend measures are calculated according to the formula:

\[ \frac{[Total\ most\ recent\ week]-[Total\ 1\ week\ prior]}{[Total\ 1\ week\ prior]} * 100 \]

New Case Trend (2 week):

New Death Trend (2 week):

New Test Trend (2 week):

Warning Level Trend

This measure indicates if the warning level has changed since the prior week.

Most Recent Epi Data

This measure indicates the most recent date that each country reported either a case or a death count greater than 0. Because the dashboard is updated weekly, dates beyond the end of the current week are not displayed.

For example, if the end of the current week being shown on the dashboard is Feb 15th:

Most Recent Testing Data

This measure indicates the most recent date that each country reported a COVID daily new tests count greater than 0. Because the dashboard is updated weekly, dates beyond the end of the current week are not displayed.

For example, if the end of the current week being shown on the dashboard is Feb 15th:

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