Surveillance is a core tool of public health, fundamental to capturing the course of disease and the consequences of interventions. Alexander Langmuir, who founded the CDC’s renowned Epidemic Intelligence Service (EIS), offered the still widely used definition of surveillance in a 1963 New England Journal of Medicine article: “The continued watchfulness over the distribution and trends of incidence [of a disease] through the systematic collection, consolidation, and evaluation of morbidity and mortality reports and other relevant data.” 

Since its start, we have tracked the COVID-19 pandemic with indicators of infection, disease, and death. Case reports and outbreaks, like that on the Diamond Princess cruise ship, signaled the pandemic’s start. Surveillance mechanisms were quickly implemented, following the established paradigm of monitoring positive tests, cases and outbreaks, hospitalizations, and deaths. With this pandemic, advances in data sciences supported the successful implementation of valuable, encompassing national and global databases, such as the Johns Hopkins Coronavirus Resource Center. The tracking of virus concentration in wastewater has proved to be an informative addition to the surveillance toolbox.

An article in Friday’s Denver Post addressed the decision by the Colorado Department of Public Health and Environment (CDPHE) to stop publicly reporting outbreaks in schools. The article quotes school officials who were surprised by the announcement and concerns about the implications of the change. CDPHE made the change to bring reporting of COVID-19 into alignment with how reporting for other respiratory pathogens is handled, part of the state’s plan for a return to normalcy. A change was made earlier to no longer post daily hospitalization count.  

Langmuir’s definition did not directly acknowledge that the relationships of indicators with the underlying public health problem may change over time. For COVID-19, that is certainly the case, complicating interpretation of trends over longer periods of time. The Los Angeles Times commented on this topic on Saturday. The case-fatality rate fell as clinical care improved over the pandemic’s first months; vaccination reduced the risk of severe disease and death as did the arrival of therapeutic agents, e.g., paxlovid; and the availability of home testing has undoubtedly affected reported case numbers and test positivity, as ascertained by public health agencies. The Colorado Modeling Group has used hospitalization count in its model to describe the pandemic’s course in Colorado and project where the epidemic curve is heading. Beginning around March of this year, the state’s hospitals stopped routine testing of all persons admitted. The hospitalization count had included persons admitted because of COVID-19 and persons incidentally found positive because of testing on admission. The modeling team now makes an adjustment for this change.  

Surveillance remains critical for tracking the pandemic and trends in the established indicators in the shorter-term. The response to the change in reporting described by the Denver Post is reflective of how intertwined the pandemic has become in our lives. I still track CDPHE’s dashboard, but no longer on a daily basis. And what does surveillance show for Colorado? Remarkably, the plateau at 300+ hospitalized Coloradans continues into its fifth week. 

During the Lance Armstrong era, my wife and I became avid watchers of the Tour de France, which is in progress through this month. COVID-19 is affecting the race, sending some important riders home. So far, eight test-positive riders have left the tour, but two have been allowed to remain. Fellow tour afficionados are aware that the prospects of 2021 winner, Tadej Pogačar, have likely been harmed by the departure of two key team members.  

What is the most sensitive way to track COVID-19 among riders and their support crews at the Tour? Testing protocols come from the Union Cycliste Internationale or UCI. They require pre-race testing and testing on rest days, and teams may do additional testing. A rule has been dropped that required any team with two or more riders testing positive by PCR in seven days to abandon the tour. The handling of riders (or other personnel) offers the possibility of keeping riders testing positive in the tour, as with two riders judged to have viral titers low enough to make them non-infectious and were allowed to remain in the race. This decision is left to the team physician, the tour COVID physician, and the UCI Medical Director. I am unaware of criteria for making such a decision, but I know that the race must go on.

Jonathan Samet, MD, MS
Dean, Colorado School of Public Health

Surveillance is a core tool of public health, fundamental to capturing the course of disease and the consequences of interventions. Alexander Langmuir, who founded the CDC’s renowned Epidemic Intelligence Service (EIS), offered the still widely used definition of surveillance in a 1963 New England Journal of Medicine article: “The continued watchfulness over the distribution and trends of incidence [of a disease] through the systematic collection, consolidation, and evaluation of morbidity and mortality reports and other relevant data.” 

Since its start, we have tracked the COVID-19 pandemic with indicators of infection, disease, and death. Case reports and outbreaks, like that on the Diamond Princess cruise ship, signaled the pandemic’s start. Surveillance mechanisms were quickly implemented, following the established paradigm of monitoring positive tests, cases and outbreaks, hospitalizations, and deaths. With this pandemic, advances in data sciences supported the successful implementation of valuable, encompassing national and global databases, such as the Johns Hopkins Coronavirus Resource Center. The tracking of virus concentration in wastewater has proved to be an informative addition to the surveillance toolbox.

An article in Friday’s Denver Post addressed the decision by the Colorado Department of Public Health and Environment (CDPHE) to stop publicly reporting outbreaks in schools. The article quotes school officials who were surprised by the announcement and concerns about the implications of the change. CDPHE made the change to bring reporting of COVID-19 into alignment with how reporting for other respiratory pathogens is handled, part of the state’s plan for a return to normalcy. A change was made earlier to no longer post daily hospitalization count.  

Langmuir’s definition did not directly acknowledge that the relationships of indicators with the underlying public health problem may change over time. For COVID-19, that is certainly the case, complicating interpretation of trends over longer periods of time. The Los Angeles Times commented on this topic on Saturday. The case-fatality rate fell as clinical care improved over the pandemic’s first months; vaccination reduced the risk of severe disease and death as did the arrival of therapeutic agents, e.g., paxlovid; and the availability of home testing has undoubtedly affected reported case numbers and test positivity, as ascertained by public health agencies. The Colorado Modeling Group has used hospitalization count in its model to describe the pandemic’s course in Colorado and project where the epidemic curve is heading. Beginning around March of this year, the state’s hospitals stopped routine testing of all persons admitted. The hospitalization count had included persons admitted because of COVID-19 and persons incidentally found positive because of testing on admission. The modeling team now makes an adjustment for this change.  

Surveillance remains critical for tracking the pandemic and trends in the established indicators in the shorter-term. The response to the change in reporting described by the Denver Post is reflective of how intertwined the pandemic has become in our lives. I still track CDPHE’s dashboard, but no longer on a daily basis. And what does surveillance show for Colorado? Remarkably, the plateau at 300+ hospitalized Coloradans continues into its fifth week. 

During the Lance Armstrong era, my wife and I became avid watchers of the Tour de France, which is in progress through this month. COVID-19 is affecting the race, sending some important riders home. So far, eight test-positive riders have left the tour, but two have been allowed to remain. Fellow tour afficionados are aware that the prospects of 2021 winner, Tadej Pogačar, have likely been harmed by the departure of two key team members.  

What is the most sensitive way to track COVID-19 among riders and their support crews at the Tour? Testing protocols come from the Union Cycliste Internationale or UCI. They require pre-race testing and testing on rest days, and teams may do additional testing. A rule has been dropped that required any team with two or more riders testing positive by PCR in seven days to abandon the tour. The handling of riders (or other personnel) offers the possibility of keeping riders testing positive in the tour, as with two riders judged to have viral titers low enough to make them non-infectious and were allowed to remain in the race. This decision is left to the team physician, the tour COVID physician, and the UCI Medical Director. I am unaware of criteria for making such a decision, but I know that the race must go on.

Jonathan Samet, MD, MS
Dean, Colorado School of Public Health