COVID-19 from the inside out: An epidemiologic perspective

As the coronavirus has taken over lives — and the news cycle — it can be hard to keep up with all of the information and make sense of it.

So said Yvonne Johnston, associate professor and founding director of Binghamton University’s Master of Public Health program, who presented “An Epidemiologic Perspective on the Coronavirus Pandemic” at the April 23 Sustainable Communities Transdisciplinary Area of Excellence talk.

Providing what she termed a broad overview, Johnston took the audience from the very beginning of the pandemic to what’s happening now, including the pathophysiology of the disease, how it spreads and what’s being done to address it.

The actual name of the novel virus is SARS-CoV-2, she said, which stands for Severe Acute Respiratory Syndrome Coronavirus 2. “It gets its name, coronavirus, because of its shape and it’s the second SARS virus to cause an epidemic. Also, we call it novel because it’s new,” she said. “It’s believed to be a zoonosis, meaning it was transferred from animal to human and there is evidence in the genome of the virus to suggest that.” Most scientists believe it came from bats, but we are not totally sure, she added.

Johnston showed a time lapse map of the spread of COVID-19 (the disease caused by the virus), originating in Wuhan, China, spreading to Europe and then coming to the United States, first appearing in the U.S. near major cities with international airports. “We’re a global community and it spread like wildfire around the world, resulting in a pandemic,” she said. A second time lapse chart demonstrated the growth of confirmed cases, with the U.S. becoming the country with the greatest number of infections over time.

She explained the epidemic curve and the R₀ (pronounced R-naught) — the reproduction number that describes how many people, on average, that a person with the virus infects. “For Ebola, for example, the R₀ is between 1.6 and 2, for H1N1 between 1.2 and 1.6 and for this coronavirus it’s 2 to 2.5, which means that for every person with COVID-19, they spread the virus to 2 to 2.5 others,” she said.

“The way that you end an epidemic is to get the R₀ down to less than one and then you will see a decline in the epidemic curve over time,” she said. “Everyone is staying at home trying to ‘flatten the curve,’ in other words trying to slow the spread and reduce the R0 so the number of people with infections doesn’t increase at such a rapid rate that we overrun the healthcare system.”

But as we follow the curve, we don’t really know when it will start to bend, she noted. “It is like a map that shows the paths that a hurricane can take. Where is the hurricane going to go? There are models trying to predict how the virus is going to spread based on certain factors, but scientists continue to revise their models as they learn new information, which changes the anticipated trajectory of the curve.”

In describing the actual virus, Johnston said it is a single-stranded RNA virus that looks like a “spiky ball” because it has numerous proteins that project out from its surface, giving the appearance of a crown or “corona” around the virus. She noted that it took about five months to decipher the genetic code for SARS-CoV-1 (the first SARS virus), but scientists cracked the code for SARS-CoV-2 in about a month. Scientists believe there are already eight different strains of the novel coronavirus, and are tracking them globally.

The virus replicates in the body by attaching to receptors on the cell surface, and once inside, it breaks itself apart and then the RNA genetic material takes over. “Viruses use the cell’s own machinery to produce the proteins needed for making new viruses,” Johnston said. “The new virus particles bud off, infecting nearby cells. If they get into the bloodstream, it’s a taxiway to every other part of the body. We call most viruses intracellular parasites because if they’re not inside a cell, they can’t replicate.”

People have a non-specific response to the virus similar to what happens when you hit your thumb with a hammer, Johnston said. “We have an inflammatory response to tissue injury — redness, swelling, heat and pain — and it is the same reaction no matter what caused it. Although it’s meant to destroy an invading organism, the swelling from the inflammatory response can cause severe congestion and extensive damage to the lungs and other vital organs,” she said.

People also have a specific response to foreign viral invaders, when our body is able to identify the virus and say, “That doesn’t belong here,” Johnston said. “The viral replication inside the body is exponential and our immune system responds by creating antibodies designed to recognize the particular virus, alarm the body’s defenses and destroy it.”

There are two types of tests — one for the virus and one for antibodies. There is a period of time between onset of a viral infection and the production of antibodies, and this is called the “window period.” During this time, a test for the virus will be positive but a test for antibodies will be negative, Johnston said. “Antibody testing is done to determine the presence or level of immunoglobulins that will indicate whether or not you have mounted a specific immune response,” she said.

Testing, testing, testing is what it’s all about

“Tests matter in terms of which test kits are used and how they are done,” Johnston said. There are a lot of tests out there that are not approved by the Food and Drug Administration, so there is no quality control and that matters in terms of whether you can trust the results. Also, if the test is not performed correctly, it can give false results.

And there’s no such thing as a perfect test, she added: “In fact, no test is perfect and sometimes tests result in false positives (the test says you have the virus when you don’t) and false negatives (the test says you don’t have the virus when you do).” False positives on a viral test can mean people are wrongly thought to be infected and isolated unnecessarily, but of greater concern are the false negatives. With a false negative, someone is told they don’t have the virus when, in fact, they do, so they’re not isolated and are capable of spreading the virus to others.

For antibody tests that result in a false positive, someone believes that they have the antibodies when they don’t, so they think they’re protected and may not take the same level of precaution.

“It’s the false positives I really worry about in the case of antibody testing,” Johnston said. “That being said, not everyone produces antibodies, and those people have to know they’re not immune and still need to take precautions to protect themselves.”

With mass testing, there will be more false test results, so tests work best when used in a targeted manner, Johnston said.

Symptomatic vs. asymptomatic

The common symptoms of COVID-19 are fever, dry cough and fatigue. Some people get headaches, others experience body aches, some have night sweats and others may lose their sense of smell or taste. Some have shortness of breath, which is a serious sign and reason to seek medical care.

But what about those who don’t exhibit any symptoms? “These individuals are what we call asymptomatic. We really don’t know exactly how many people have gotten the virus but did not have symptoms. It is likely to be a pretty high number, perhaps as many as those who have had symptoms,” Johnston said. “The symptoms you experience are all related to chemical messengers that are released by inflammatory cells. Some of these cytokines (chemical messengers) cause the blood vessels to get leaky so fluid gets into the tissues resulting in swelling, and some cytokines raise your body temperature, which actually can help you fight the virus.”

There are also many people with the viral infection who have underlying health conditions such as diabetes, cardiovascular disease, chronic lung disease and chronic renal disease. These risk factors make it more likely that they will get very sick and need hospitalization. Some who get very sick experience what’s called “cytokine storm.” This happens when cells trying to fight the infection release so many chemical messengers into the bloodstream in such a short amount of time that it results in massive inflammation and is potentially life-threatening, Johnston said.

How best to attack COVID-19

A vaccine would be the best way to prevent COVID-19, Johnston said, and there are many people working on it, but it takes time to develop one that is safe and effective. We still do not have a vaccine for HIV, MERS or SARS-CoV-1. And even when we do have a vaccine, it might lose its effectiveness over time due the ability of the virus to mutate and avoid detection. Still, the most beneficial primary prevention strategy is vaccination.

There is also herd immunity, which is indirect protection that happens when a large proportion of a population has antibodies to the virus so the disease can no longer spread. “Acquiring herd immunity by most people getting sick is OK for a disease that makes you mildly ill for a week, but not if it kills you,” Johnston said. “To have adequate immunity in a population, you need about a 90% vaccination rate, and that’s what protects the other 10% of vulnerable individuals who can’t be vaccinated.”

Secondary prevention relates to treatment for individuals who are sick, Johnston said. She added that, as of April 1, there are 251 clinical trials specific to COVID-19 underway, and of these, 109 are examining pharmacologic therapies. The drugs under investigation target the virus in different ways, either preventing penetration of healthy cells or at some point during its replication cycle once it has already infected cells. “So although there are many ongoing studies, we do not have many good pharmacologic treatment options right now,” she said. “Some drugs that seemed promising, have been shown to be ineffective in clinical studies and other drugs have had dangerous side effects.”

Adjunctive therapies being used include interferons as immune modulators and corticosteroids as anti-inflammatories. There are also more aggressive treatments like monoclonal antibodies or convalescent plasma where you directly give people the protective antibodies. In the case of convalescent plasma, you take blood from someone who has recovered from COVID and separate out the fluid part containing antibodies and then give them to really sick people. “This is being performed now in many hospitals across the country,” Johnston said.

Tertiary prevention involves actions to minimize long-term complications and mitigate the most severe health impacts, Johnston explained. “Recognizing and treating people who are sick early in the disease process and giving them the best treatments available can help prevent an adverse event such as a heart attack, stroke or blood clot in the lungs or leg,” she said.

How the virus spreads and how we can protect ourselves

The virus is spread through small water droplets or aerosols that are released into the air when a person talks, coughs or sneezes. It can also spread when people touch objects that have been contaminated with virus particles and then touch their face or eyes.

To prevent the spread of COVID-19, use of personal protection is really important, as is especially frequent and thorough hand-washing and wearing a face mask in public. Environmental strategies are also essential, like making sure frequently touched objects and common areas are disinfected, Johnston said. “Isolating people who are sick and quarantining their close contacts as well as avoiding large gatherings of people and having everyone keep a safe physical distance, at least 6 feet apart — this is how we’re going to reduce the reproduction number (R₀) and flatten the curve,” she said.

Locally, the public health team is conducting case investigations of individuals who have tested positive for COVID-19, trying to find out information about the person: Do they have any other health conditions? How did they get it? Did they travel somewhere? What is the course of their disease? Were they hospitalized? Who did they come in contact with just days before and while they have been symptomatic?

“Those with disease are isolated until their illness resolves and their close contacts are quarantined for two weeks,” Johnston said. “Until we have an effective vaccine, case investigation, contact tracing and isolation/quarantine are the most important public health tools we have to prevent the spread of the coronavirus.”

Examining the impacts and moving forward

The social impacts of this pandemic have been enormous, Johnston said. “It has changed how we work, learn, play and pray.” And not to be minimized at all, are the effects of the epidemic on mental health including isolation, fear, anxiety, depression and substance misuse. Both the physical and mental health impacts are especially concerning for those who are most vulnerable.

Johnston explained that high-risk populations include not only those with underlying health conditions, but also those in nursing homes, prisons, jails and detention centers where the virus can spread uncontrollably. “Migrant workers and undocumented immigrants who fear deportation may not seek medical care and there are disproportionately higher rates of infection and death among those who identify as Black,” she said. “The social determinants of health, including income, race and access to health insurance factor into who becomes sick, who receives care and who recovers. The social inequalities that lead to disparities in health outcomes have been amplified in this pandemic.”

As part of our recovery, these underlying social factors that have resulted in differential effects on poor, vulnerable and marginalized populations must be remedied, Johnston said. And there are also the economic impacts: the Dow Jones has declined, the price of crude oil is hovering at an all-time low, the stock market has been exceptionally volatile, retirement accounts have dwindled, and unemployment has skyrocketed. “What we see is an inverse curve — as the number of cases goes up and we take more intense measures to protect people, the more extensive the negative impacts are on the economy,” she said.

“Amid all of the worrisome news, there are a few good things,” Johnston said. “Pollution is down and we’re able to detect earthquakes that we couldn’t before. Telehealth and telecommuting are working, people are pulling together to help one another, we’re spending more time with family and we’re gaining a deeper appreciation for what we truly value as important in our lives, but it is at such a high cost in terms of loss of life and what these losses mean to those left behind.

“So when it comes to reopening schools and businesses, it has to be done thoughtfully and safely,” she said. “It’s going to take the collective wisdom from university researchers, public health professionals, emergency planners and other community stakeholders, across the country and around the world, to figure out how we’re going to do this. We will need to use a risk management approach and err on the side of caution.”