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The Global SARS-CoV-2 Surveillance Project: Policy, Persistence & Transmission

The Global SARS-CoV-2 Surveillance Program (GASSP) has been retired effective March 15, 2023 due to the lack of reporting. However, the website will be maintained to preserve historical tracking and statistical modeling of COVID-19 transmissions and deaths.

 

Without question, SARS-CoV-2, the novel coronavirus that causes COVID-19 has resulted in an unprecedented pandemic in modern history with significant morbidity and mortality that has a deleterious impact on the global economy, violence, mental health, and food security. Public health surveillance informs the policy needed to eliminate COVID-19 which depends on a variety of metrics to identify high-priority events.

Surveillance Metrics

Surveillance Metrics

The SARS-CoV-2 Global Surveillance Project provides standard surveillance metrics that are useful and allow us to compare regions even though they are limited to more severe cases and suffer from incomplete case ascertainment and data contamination. To address these data limitations, we validated additional novel surveillance metrics of (1) speed, (2) acceleration, and (3) jerk (change in acceleration), (4) 7-Day Lag, (5) 7-Day Persistence effect.

KEY TERMS

Speed: New Cases Per Day

The basic indicator of the pandemic’s status on a given day is the number of new cases on that day. Since new cases per day is a rate (value per unit of time), we will adopt physics nomenclature and refer to this as the speed of the pandemic. This is consistent with heuristic descriptions of the pandemic as spreading rapidly (ie, a large number of new cases per day) or slowly (i.e., a small number of new cases per day). The public health ideal is to bring the speed of the pandemic to zero.

Acceleration

We are also interested in whether the number of cases per day is increasing, peaking, or decreasing, and why? Again, we will adopt physics nomenclature and refer to this as acceleration. Since acceleration is difficult to ascertain on a daily basis, and there are weekend effects, etc., in the data, we report the weekly average for the acceleration. A positive acceleration indicates an increasing number of cases per day, and a negative acceleration (deceleration) indicates a decreasing number of cases per day. An acceleration of 0 is indicative of a peak, valley, or inflection point depending in part on whether the previous acceleration was positive or negative.

Jerk: The Change in Acceleration

We now address the question of whether the day-to-day increase (or decrease) in new cases the current week is bigger or smaller than the day-to-day increase (or decrease) in new cases compared to the past week.Using physics nomenclature, the difference between these two acceleration rates is the “jerk.” A positive jerk indicates that the acceleration in the number of daily cases this week is greater than the average growth last week. Such a finding would be consistent with a scenario in which the pandemic was experiencing explosive growth; where a policy shift such as reopening had augmented the acceleration of the pandemic, possibly including a shift from deceleration to acceleration; or where super spreader events had “jerked” the acceleration upward, among other scenarios

7-Day Persistence Effect

The statistical impact of the 7-Day Lag of Speed on today’s value of Speed. New cases per day tend to have an echo effect seven days later, similar to the echo effect in the population pyramid caused by the baby boom. Reported as the weekly average number of new cases per day that are attributable to the weekly average of the 7-DayLag of the number of new cases per day.

Global SARS-CoV-2 Surveillance Dashboard

The basic question we are trying to inform is: how are we doing this week relative to previous weeks? From a public health perspective, in the midst of a pandemic, we would like (at least) three affirmative responses: (1) there are fewer new cases per day this week than last week, (2) the number of new cases is declining from day to day, and (3) the day-to-day decline in the number of cases is even bigger this week than last week. Additionally, we would like some indicative information about significant shifts in how the pandemic is progressing —positive shifts could be the first indicators of the emergence of a new or recurrent hotspot, and negative shifts could be the first indicators of successful public health policy.

VIEW DASHBOARD

GASSP Featured Website

The International Food Policy Research Institute (IFPRI)

The International Food Policy Research Institute (IFPRI)

IFPRI provides research-based policy solutions to sustainably reduce poverty and end hunger and malnutrition in developing countries. IFPRI’s vision is a world free of hunger and malnutrition. Its mission is to provide research-based policy solutions that sustainably reduce poverty and end hunger and malnutrition. Their regional and country programs play a critical role in responding to demand for food policy research and in delivering holistic support for country-led development.