Ask the Expert: The Epidemiology of COVID-19
By Brian Hiro
Dr. Deborah Morton is accustomed to receiving quizzical looks when she tells people she’s an epidemiologist.
“You tell them what you do, and they’ll say, ‘Oh, are you a skin doctor?’ ” Morton said with a laugh.
The coronavirus epidemic, however, has thrust epidemiology – the study of the incidence, distribution and control of disease in a population – to the forefront of scientific disciplines across the globe and even made temporary celebrities out of some of its practitioners.
It all has translated into a heady experience for Morton, an assistant professor in the Master of Public Health program and one of only two epidemiologists on the Cal State San Marcos faculty. Her expertise lies in chronic disease epidemiology such as diabetes more than in infectious disease epidemiology like COVID-19, and she has served in an academic research environment rather than the climate of an active public health department. But the principles of epidemiology are the same regardless of background.
“The COVID-19 crisis has been interesting, and I’m hopeful it translates into a broader interest for public health education and training for programs like ours when this calms down,” she said.
In this edition of Ask the Expert, we talk to Morton about epidemiology and COVID-19.
Question: Though you don't specialize in infectious diseases, as someone who does this for a living, I imagine you’ve been fascinated by the coronavirus and tracking it pretty closely. What has been your main reaction to seeing its march across the globe?
Deborah Morton: At one level, so many deaths worldwide and stories of people dying alone without their families is heartbreaking. From an academic perspective, yes, fascinating to watch a pandemic unfold and evolve in real time before our eyes and on our computer screens. Usually we only know pandemics through history and teaching. Public health education for graduate students requires core knowledge of epidemiology. One of the major principles of epidemiology, which originated due to infectious disease, is the process of how epidemiologists investigate outbreaks and how to proceed with identification of the pathogen, course of the disease, transmission, control of the epidemic, treatment and continued surveillance. The epidemic curve, a major principle of epidemiology, is now big news every day – how the curve moves, how it operates, what direction it takes and how predictive it is of the future case and death rates. And with infectious disease, it happens the same way each time. The left-hand side of the curve goes up very fast when there's an outbreak, and then the right-hand side of the curve, as it comes down, is a more rocky, up-and-down pattern that spans a much longer time period. All of this talk about flattening the curve has become standard language that the general public is beginning to understand – a core piece of the content of a course in epidemiology. Many epidemiologists are being consulted and living in the spotlight as experts for how to proceed and predict the future of the pandemic. A highly unusual and historic situation.
Q: What are your thoughts about where things stand right now, both in the U.S. and worldwide?
DM: One of the major issues that keeps getting brought up is testing, a very important concept in epidemiology. We teach calculations for sensitivity and specificity of tests along with the positive and negative predictive value associated with a test. How well does the test identify the pathogen? Does it accurately and reliably identify the people who have the disease along with those who don't have the disease? Do we need an additional confirmatory test? How many false positives are there? How many false negatives are there? It’s a two-by-two table – disease, no disease, exposure, no exposure – and those four cells in that little table explain everything.
Right now, we don't know what the sensitivity or the specificity is of the test they're using to identify COVID, and we're not yet keeping track of the people who have survived – we don't have that number. However, it is one of the key components that fits into the two-by-two table so sensitivity and specificity can be calculated. Not people who had to go to the hospital and not people who died, but the survivors who have antibodies and people who were never tested for COVID itself. These numbers are one of the major puzzle pieces that will take time for the world to know and that we must have for future planning and dealing with recurring outbreaks, which will also happen.
Q: What would be your primary piece of advice to your students and other people in the campus community?
DM: Do what you're told by local public health officials because they are the authorities. Generally in a pandemic, the president is not giving updates. It's U.S. Public Health or the CDC that give updates. And in San Diego County, Public Health Services does that every day. Just do what you're told and convince your family to do the same. When they issue a stay-at-home order, they mean it. Public health doesn't ever make decisions or recommendations lightly.
Q: As an epidemiologist, what in particular strikes you about the numbers or the trends you’re seeing?
DM: When you look at the Johns Hopkins map that plots all the cases, if you notice, in South America and Africa there have been fewer cases. There are cases all over those continents, and that could be due to inaccurate surveillance and reporting, but they haven't gotten to the level of China, Italy, Spain or New York. I'm wondering if that has something to do with climate. Viruses like cold weather. For instance, influenza likes cold weather, and it travels around the globe every year. That's why it comes back in the fall. So I'm wondering if this is a virus that when the weather warms up, it will help control the transmission. I'm hoping that's the case. That will be known at some point.
Q: You’ve done a lot of work with the California Indian Culture and Sovereignty Center at CSUSM and with tribal/reservation communities in general. What do you think about COVID-19 as it relates to underrepresented minority populations, and what are their unique challenges and risks right now?
DM: Minority populations are already compromised in a thousand different ways. They have higher rates of chronic disease, they have higher rates of heart disease, and they have higher rates of diseases affecting the lungs. The two leading causes of death in the United States are heart disease and cancer – that’s true for everybody, no matter your age, gender or ethnicity. But minority populations have a higher prevalence rate of chronic disease because they don't have access to good health care. American Indians are entitled to health care by Indian Health Service, a division of the U.S. Department of Health and Human Services. They have hospitals and clinics all over the country, but the care is substandard because they're in remote locations, which is where most Indians live who utilize Indian Health Service. There are 5.2 million American Indians, and only about half are cared for by Indian Health Service. A lot of those patients are from reservation populations. At this point, in all of IHS facilities across the United States, there are 10 ventilators and six ICU beds! These facilities are not funded properly, and seriously demonstrate how minority populations are not cared for with equity, especially American Indians.
Q: Why does COVID affect people with underlying health issues more seriously?
DM: We all understand that if a virus, such as a new novel virus, targets your lungs and if your lungs are already compromised, then you have less of a fighting chance than someone who doesn't have underlying comorbidities. But we might not completely understand how a chronic disease such as diabetes compromises your body as well if infected with an additional virus. American Indian populations have diabetes at twice the rate, sometimes three times the rate as the non-Indian U.S. population. And just having diabetes is an independent risk factor for heart disease. So the longer you have type 2 diabetes, the more likely you are to develop heart disease as well. As a population, that puts American Indians at greater risk immediately whether they're an elder or not.
All of the people in this country who are members of minority populations where there are health disparities are at much greater risk than anybody else, whatever the health disparity may be, despite ethnicity, age or zip code.
Q: What lessons can be applied from past pandemics?
DM: Everything we know about pandemics can be applied to the current situation. Certainly testing. Certainly procedures when the test does not have known high sensitivity or specificity. Certainly how long it takes to produce a safe and effective vaccine, and certainly treatment. There's no treatment for COVID-19 right now. I’m reminded of HIV when it first emerged; nobody knew what it was. It took a very long time, many years in fact, to develop appropriate drugs that now make HIV a treatable chronic disease. At the beginning of the HIV epidemic, we didn't know how it was transmitted either for a very long time. The country was scared, to say the least. So, yes, of course we can learn from our history, the perfect example being Dr. Anthony Fauci, a force who helped change the world for those who contracted HIV back in the 1980s and has now re-emerged as an important and respected leader during this COVID crisis.
Q: This seems to be the question on everyone's mind. How long do you think it will take to get a handle on this and resume normal activities?
DM: As an epidemiologist, my interest is always data-driven. In a recent article, looking at the epidemic curves of the top five global health infectious diseases being continuously surveilled, we can see usual time frames for the lengths of those epidemics. Starting with Zika virus, the first report of it in West Africa was in February 2014; the curve continued to rise until about October and then started to decline. However, not until two years later, in January 2016, was it declared over as an epidemic. For MERS, another coronavirus that hit in Saudi Arabia, beginning in May 2013, it reached its peak, then declined. In April 2014, the curve rose back up again, this time higher than the first time. Epidemics can go on and on and on, because of a country’s resources, vaccine development and equity in treatment. So you are asking the million-dollar question.
Cases in California are not skyrocketing like they have in New York or in Seattle, and maybe will not because of the measures we've taken in the state and the leadership of Gov. Newsom. But for us in California, we really don’t have a clue yet what’s going to happen because we don’t know when the curve will reach its peak. I'm thinking we won't be back to the new normal until June or July. Even when the curve recedes, there will be spikes in the curve surging back up again.
Q: So you could envision normal activities resuming in early-to-mid summer and then, based on what happens with the curve, future social distancing measures might be required?
DM: Yes, social distancing will be extended because until we have a vaccine, COVID can only be controlled by behaviors, personal protective equipment, and isolation and quarantine for those who are sick because of the highly contagious nature of COVID and its ability to survive for up to nine days in the environment.
Q: I've heard the epidemic curve described as more of a roller coaster because it’s not a steady decline. Do you agree with that?
DM: Yes, that’s what will happen. When there’s an epidemic and it ramps up with many deaths, that's news and everybody hears about it. But then when the epidemic peaks and starts to come back down, the news goes on to something else and we don't hear about the fact that it takes possibly 18 months to two to three years before that epidemic is considered over and under control by public health officials. Look at the Ebola outbreak in West Africa several years ago. We all heard about it in the news and the Americans who were sent home, treated and survived. But we never heard about when the epidemic in Africa was officially over. We know it ended, but we were never told when it ended. And COVID-19 will probably follow the same pattern because it's a highly contagious virus and viruses are known to be similar in their outbreak patterns.
Brian Hiro, Communications Specialist
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