Vaidehi Shah

By Megan Willome

Epidemiologist talks about what we’ve learned so far

The official guidelines that have been recently issued to slow the spread of COVID-19 come down to one old-fashioned word: etiquette. We wash our hands, wear face masks and practice social distancing in an expression of kindness to our neighbors. “Etiquette” is a word Vaidehi Shah, senior epidemiologist at Waco-McLennan County Public Health District, used when explaining what we need to do to keep each other safe and well.

“The message still stands: Wash your hands for 20 seconds with soap and water. If you don’t have soap and water available, use a hand sanitizer,” she said. “The advice stands to respect the etiquette that we’ve been promoting since the beginning of the pandemic. Cover your face if you cough or sneeze. If you are sick, stay home. Definitely practice social distancing and wear a face covering in public all the time.”

Shah worked as a dentist in Mumbai, India, before coming to the U.S. Originally she planned to practice dentistry here but was advised to pursue a master’s first. She attended Texas A&M University to get a degree in public health, and along the way, fell in love with epidemiology.

“By the end of my first year I knew that I would like to be an epidemiologist and have never once regretted my decision,” Shah said.

She came to Waco in 2015 to join the public health district and in 2017 was promoted to senior epidemiologist.

Wacoan writer Megan Willome spoke with Shah by phone to find out what we’ve learned about the virus, what trends are emerging and what we can do to prevent the spread.

WACOAN: Explain what you do as an epidemiologist.

Shah: Epidemiology, for what we do, there are two words I generally use: ‘disease surveillance.’ The epidemiology program is split into the infectious disease and chronic disease branch.

With infectious disease, Texas has a law which requires physicians or laboratories to report a list of about 90 conditions to us [public health departments]. COVID-19 has been added to that list.

We conduct the investigation on a person, getting demographics, asking questions to find out how they got the disease during the incubation period. For COVID-19, it’s two to 14 days.

For a foodborne illness, we ask, ‘Did you go to a restaurant? Did you go to a party?’ For COVID-19, we ask, ‘Did you travel somewhere? Did you get exposed to someone who has COVID-19? What did you do during your contagious period? Did you go to work? Did you go out in the general public?’ That’s contact tracing. Anybody exposed during those contagious periods should be quarantined.

Then we [determine] do you meet the criteria for isolation?

WACOAN: How do you define close contact when you are doing contact tracing and identifying those who came in contact with the infected person?

Shah: Close contact is less than 6 feet and more than 15 minutes.

The health district is conducting the majority of the investigations. Once those are conducted, we refer those identified as close contacts — who came in contact with an infected person outside the household — that information is sent to the state [health] department. Then the state talks to those close contacts and lets them know they need to be quarantining for 14 days. They will call for 14 days, ask about symptoms, ask if they are staying home.

I have been concentrating on the data for COVID-19 in Waco and McLennan County.

WACOAN: Are you behind the data on the site?

Shah: Yes. We have three epidemiologists in house. We do the data on the COVID-19 Waco website, except for testing counts. We get those from Heart of Texas Regional Advisory Council. All other data points on the website come directly from the health district.

WACOAN: Can you go over the incubation period again?

Shah: The incubation period for COVID-19 is two to 14 days. That is the time period from the date you are exposed to the date you have symptoms. The median in the majority of cases is six days.

That is where contact tracing plays an important role. Once we identify someone who has been in contact with someone with COVID-19 and may have been exposed, we want them to quarantine. We want to identify everyone they’ve been in contact with during that contagious period.

The contagious period is 48 hours before the onset of symptoms to at least 10 days after symptom onset.

WACOAN: And isolation refers to separating people who are actually infected with COVID-19?

Shah: Yes. There are specific guidelines from [Centers for Disease Control] to discontinue isolation: 10 days from symptom onset, fever-free for 72 hours and symptoms improving.

We have a high prevalence of the disease in McLennan County and in the country overall. And due to the fact that several people are mildly symptomatic or pre-symptomatic or even asymptomatic, you don’t know who has COVID-19.

The best protection is to reduce your going out of the house, and if you have to leave the house wear a mask and maintain that 6-foot distance.

WACOAN: Explain how wearing a mask and social distancing work together.

Shah: Let’s talk about 6 feet first. The reason 6 feet came into recommendation is because there have been studies that prove that when you’re talking or coughing or sneezing, droplets come out. Due to gravity, they usually do not go beyond 6 feet. It’s those droplets, those respiratory secretions [that put you at risk]. You want to be away from anyone exuding those droplets. If you maintain that 6-feet distance, you are limiting your exposure of coming in contact with COVID-19.

When you wear a mask, it’s the mask that’s absorbing those droplets. It’s not eliminating risk, but it’s reducing risk even more. You still should be maintaining 6 feet of distance, but if you can’t maintain that distance, then wearing the mask is limiting the spread to other people. Wearing a mask is considered source control. If both individuals are wearing masks, it reduces the risk even more. I like to say that wearing a mask does not eliminate the need to social distance, but if you can’t social distance, then wear a mask. And the other way around.

Just wearing a mask is not enough. You must be social distancing as well.

WACOAN: Going back to being quarantined if a person is exposed, why should they wait to see if they develop symptoms when they could simply get tested for COVID-19? Who should be getting tested?

Shah: If you are symptomatic, yes, definitely get tested.

Second, if you’re exposed to someone who has tested positive and you get symptoms, then get tested.

If you are exposed to someone who has tested positive and you don’t get symptoms, then what the health district does is recommend that if you’re not symptomatic, then we’re not recommending testing — except for in certain conditions, like in a nursing home or a jail, where we want everyone to be tested because everyone is in a high-risk zone and we want to catch all positive cases. Anywhere we consider it a congregate setting or a group at higher risk needs to be tested.

For the general public, let me put it this way: If I test positive and you came in contact with me yesterday, and you get tested tomorrow and test negative, that negative test just tells you that you were negative that day. You may still develop symptoms between two to 14 days after exposure. People have a false sense of security. If you have been exposed to someone who tests positive, you should be in quarantine for 14 days, even if you’re not symptomatic. If you are concerned because you are at high risk or have underlying conditions or are over 65, talk to your health care provider on when you should be tested and if you should be tested.

WACOAN: People are confused about where to turn for advice right now. Where is the best place for people to go for accurate information?

Shah: The CDC website, [], has up-to-date information. has information specifically if you want local [data], location of testing sites, what orders are in place, what resources are available.

WACOAN: With the recent news that hospitals must begin reporting to the Department of Health and Human Services instead of the CDC, will the CDC’s website still be a good resource?

Shah: The health district continues to follow and rely on the guidance as provided by the CDC and the Texas Department of State Health Services for all diseases including COVID-19, and they remain to be resources for McLennan County residents as well. That information is available for the general public.

WACOAN: How is this virus typical and how is it atypical?

Shah: I would say initially we saw the typical symptoms — shortness of breath, cough, fever — those are typical symptoms of respiratory illness. But we have identified loss of taste and smell in several cases, which is atypical of respiratory illness. It’s certain people, not everyone, but we have seen it in quite a few cases, in the majority of people. But COVID-19 does not have a classic symptom that if you have that symptom then we know for sure, which makes it difficult to identify the disease.

Another thing that is atypical is most respiratory diseases spread when you have symptoms. With COVID-19, we have identified that individuals who are mildly symptomatic, almost asymptomatic, or who are just 48 hours before symptom onset also can spread the disease, so that makes it difficult to contain.

WACOAN: As we get into the fall, we enter flu season. What do you expect when we have both the seasonal flu and the coronavirus circulating?

Shah: I’m scared. The reason I say that is we have seen that summer has not seen a lower number of cases. One reason you can attribute to the increase in cases is that we opened the state. We have more activity than when we were sheltering in place.

Fall usually is flu season. We start seeing an increase by September and October, then we have a higher number toward the end of one year and the beginning of the next. Flu and COVID-19 have very similar symptoms. We will see an increase in flu cases as well as COVID-19 cases, and it will be difficult to differentiate between the two. If we continue to reopen and resume all the daily activities that we do in the fall, we will see more cases.

WACOAN: Is it true that underlying conditions can impact COVID-19 and cause complications?

Shah: In the initial few months, when we mostly saw cases in elderly adults, underlying conditions was a huge role, and underlying conditions do play a huge role right now. You are at higher risk if you have underlying conditions. But with the last couple of months, we’ve seen a lot of younger populations being infected with COVID-19. In Waco we have a huge amount of 20- to 29-year-olds that are getting COVID-19, in people where we have not seen that many underlying conditions. We have seen hospitalizations in this age group.

WACOAN: I looked at the data on and it appears that race is a factor locally, with Hispanics accounting for 66% of positive cases.

Shah: We’re seeing it nationally, too, in the country. The CDC shows similar data. There is a huge increase among the population that is Hispanic, followed by African Americans, followed by white/non-Hispanic.

From my understanding, from analyzing data from the past couple of months, when we started seeing cases in March, we were seeing a higher number of travel-related cases. At that time we did see the highest number of the infected population was white/non-Hispanic. Over a period of time, in the past month, we’ve seen an increase in cases in individuals who are of Hispanic ethnicity and individuals who work at essential jobs, like meat-packing plants or in other lower socioeconomic workplaces. It shows that the disease is now prevalent in communities and has reached all sectors of the community.

There was a graph that Mayor [Kyle] Deaver showed in a press conference, that showed the change in COVID-19 over the last four months. The line for whites stays stagnant, while the lines for Hispanics and African Americans was low but then has increased exponentially. We have coalitions addressing this issue, and the mayor has groups that are working on it. At the health district, we have programs that we are building to target vulnerable populations in the community.

WACOAN: How can people access those resources when they are completed?

Shah: It will be available at the website.

WACOAN: Do we know anything about how people recover from the virus or how to boost immunity?

Shah: That would be outside my professional expertise. A physician would be better able to answer.

WACOAN: What do you want to say to Wacoans? What do we need to do?

Shah: You should follow mask guidelines and practice social distancing — I can’t give a deadline or end date. Do as much as you can or all the time.

Face coverings will reduce your risk of getting the virus or spreading the virus, especially if you cannot maintain social distancing. Follow respiratory etiquette that has been recommended for months. I want to emphasize that as much as we can.

One reason for the increase in cases is the increase in social activities. If you can limit social activities, you should. We have technology; let’s use technology to talk to our loved ones. If you have someone high risk in the same household, anybody at higher risk of severe illness and higher risk of a fatal outcome, make sure you are doing everything to follow the guidelines. It will protect them.

WACOAN: Is there anything else we should know?

Shah: Anybody who is tested for COVID-19, they need to be quarantining themselves at their house until they receive test results. Some people wait for test results before they quarantine. We’re losing precious time and spreading the disease. If you are getting tested, stay home while waiting for your results. If your results are positive, the person who tested positive, along with the household members, should be isolating, should be staying at home.