Zack Moore, a state epidemiologist in North Carolina, said he could not say exactly how many people in the state were infected with the new coronavirus,media outlet The Verge reported. He knows how many people test positive for new crowns every day, how many people in the state see a doctor in a hospital, and so on. None of these figures alone indicates how many people have been infected. But these figures, combined, help to outline the pandemic.
“It’s never been a single source of data,” he says. Each data source helps, but they have their own limitations. So combine them. “
Public health experts have no way to really count everyone who has a disease at any given time, even for a disease like the flu. Instead, they combine different data sources to make the best estimates of the outbreak. The aim is to have a deep understanding of the virus to make these estimates as accurate as possible.
“People think we know exactly how many people get the flu each year, but we don’t know,” Moore said. “We must use these monitoring tools and indirect measures to gain a comprehensive understanding. “
Public health officials are measuring the COVID-19 pandemic in a few ways. John Brownstein, infectious disease epidemiologist and chief innovation officer at Boston Children’s Hospital, said the number of positive test results is an important statistic. “These data are very valuable because it is a diagnosed disease, ” he said. But it’s an imperfect tool because most communities in the U.S. don’t have enough testing to detect every suspected patient.
Because not everyone who gets sick will be tested, experts have also looked at data collected by hospital emergency department patients. These measurements also have limitations, as many people with these symptoms may simply have flu or other types of respiratory disease. This method also misses people who may feel uncomfortable but don’t go to the hospital.
Further amplification, some researchers have developed programs that require people to report their feelings every day. They hope the data will help reveal hot spots where people are starting to feel uncomfortable but haven’t been tested for COVID-19. Another big-picture strategy is to measure the level of new coronaviruses in sewer systems to predict how many people in a community are infected. Antibody testing, which can check whether someone has been exposed to a virus in the past, is also a key tool. They can help find people who have never felt unwell and are therefore not caught by any monitoring methods for screening for symptoms.
“We’re constantly trying to bring together different pieces of information that provide a different perspective to see an outbreak,” Brownstein said. “
In North Carolina, Moore looks at all of their data sources daily and weekly and looks at trends in those data. If the number of people who go to the emergency room with COVID-19 symptoms is declining, but the number of hospitalizations and those who test positive is still rising, it may just mean that people are avoiding the emergency room — rather than saying fewer people are sick. “It has to be looked at in a bigger context,” he said. “Trends are something we need to focus on because it helps us make control decisions. “
Moore says they’re looking closely at the monitoring tools they haven’t used yet to see what might be a useful addition to their data sets. “We want to know if they really add value,” he said. “We don’t want to make more noise – surveillance is confusing enough. “
Ongoing research on the virus and how it spreads will also help experts find the best way to interpret the data they collect. For example, studies that collect blood samples to detect antibodies in some populations will help determine the proportion of people infected with coronaviruses without feeling unwell. With this data, public health officials will be able to more accurately estimate the number of new coronal patients and use the information they collect to report symptoms.