COVID-19 Tests: Everything You Need to Know
Testing for COVID-19 in Houston, and around the world
Testing for SARS-CoV-2, the virus that causes COVID-19, started back in January of 2020 and has continued since. The U.S. has currently conducted more tests than any other country — currently a whopping 359 million. For context, India, second on the list and with a population four times the size of the U.S., has only done 219 million tests. While that may seem impressive at first, in reality, the U.S. ranks 22nd if we look at tests done per 1 million people, falling behind both Hong Kong (20th) and the UK (15th). Considering that almost 29 million of the total 116 million reported cases of COVID-19 worldwide occurred in the U.S., the situation is quite dire.
Texas itself has done over 23 million tests so far and continues to conduct almost 100 thousand new tests every day. Over 3.8 million of those tests occurred in Harris County, by far the highest of any county in Texas, with Dallas coming in a distant second at 2.3. Texas is unfortunately at the lower end of the testing spectrum compared to most other states.
When looking at the positivity rate (the number of tests that come back positive), the numbers are even more worrisome. The higher the number, the more prevalent the virus is within the population.
As of the time of writing, Texas’ positivity rate has doubled, jumping from 6 percent to 12. That’s why it’s more important than ever to stay vigilant — wear a mask, stay six feet away from others, wash your hands often, and avoid crowds.
Why are COVID-19 tests so important?
As mentioned earlier, one of the ways that we can tell how we are doing is to look at the positivity rate. If you have to test a lot of people to find someone who tests positive, that’s a good thing, because it means there aren’t a lot of people who are sick. Conversely, if you find that a lot of your tests are coming back positive, more people are sick, and that means the virus is spreading more rapidly. For the positivity rate calculations to be as accurate and as useful as possible, we need as many tests as possible — more tests mean we can get a better measurement of the transmission rate. We can then use this information to prioritize where to focus our efforts.
Additionally, this study shows that people are most infectious during the period before they show any symptoms, and this study concluded that 43 percent of the patients they monitored never developed any symptoms at all. This is one of the reasons that the virus spreads so quickly — people who are spreading the virus don’t even know they are infected in the first place.
With testing and tools like contact tracing, we can determine who is spreading the illness and who they might have inadvertently infected, which allows us to more effectively manage the spread of the virus.
Should I get tested for COVID-19?
If you think you may have been in contact with someone who has tested positive for COVID-19, you should probably get tested — but don’t rush out and get a test immediately. The virus may not be detectable yet, and the test will probably say that you aren’t sick, even though you are. Instead, you should quarantine yourself for five days, and then see if you can book an appointment for a test. If you can’t get tested, the Texas Health Department recommends that you do not leave your home until it has been at least 10 days since your first symptoms appeared, and you are fever-free for at least 24 hours without using any fever-reducing medications. If you aren’t sure if you should get tested, you can use this COVID-19 Self-Checker, or contact your doctor.
If you develop any of the emergency warning signs for COVID-19, call 911 immediately. Signs include:
Trouble breathing
Pain or pressure in the chest
Confusion or inability to wake up/stay awake
Bluish lips/face
How do the COVID-19 tests work?
There are currently three main types of tests used for COVID-19:
Antigen - Antigen uses a throat or nasal swab to test for the presence of the virus. This determines if there is currently an active infection and helps identify those who are contagious to others. While it is the cheapest and quickest method, producing results in less than an hour, it comes with some caveats — these tests are more prone to false negatives, so they are more likely to miss active infections. However, if it does come back positive, it’s almost certainly correct, and the fast turn-around means that it’s useful when screening large numbers of people.
Molecular - Molecular uses a nasal/throat swab as well, but some tests use a saliva sample instead, which is more comfortable and less intimidating. They are more accurate than antigen tests, but it can take much longer to get test results depending on whether the sample can be analyzed on-site, or must be sent to an outside lab. Luckily there are kits available for self-testing at home which can provide results in around 30 minutes, no lab required. But in general, molecular tests are more expensive to produce. And while they may be more accurate, some people can test positive even when they are no longer contagious to other people, and yet others will only test positive in the first few days of the infection, after which the test will be inconclusive.
Antibody/serology - Antibody tests use a blood sample to determine if a person has had a COVID-19 infection in the past — they do not work on a current infection. They are useful in determining how many people were infected in a community, which can tell us what percentage of people have already had the infection. However, some of these tests have a low sensitivity, which means that many results will be false positives. They also may react with other coronaviruses, even those that do not cause COVID-19, which produce even more false positives. Testing positive does not necessarily mean that you are immune to the virus, either, as we currently don’t know for sure that a second infection is not possible.
Each of these tests has a different use and each is equally important.
Additionally, there is a test called the polymerase chain reaction (PCR) test. Done with nose swab, this test is actually known to be one of the most accurate tests out there. In order to test for the presence of COVID-19, it uses chemicals and a PCR machine (or thermal cycler). This causes a chemical reaction in which it makes copies out of the genetic material found in COVID-19. If the virus is present, the sample will emit a fluorescent light.
Where do I go to get tested for COVID-19?
Before you get tested, you should contact your doctor. They can confirm that you should be tested, and some of the testing locations do require a referral. You can also check this link here to find a test location site in Texas — many of them are completely free. It’s best to call ahead or visit the testing location website before heading there, as each site has different requirements and operating hours.
At Willowchase, we offer COVID-19 rapid testing where you can actually get your results in 15 minutes or less. It’s great for families within the Houston area, or for families who need a doctor that speaks English/Vietnamese/Spanish.
More specifically, we use the antigen test to get you rapid results—so you’ll get a quick nasal swab and then be on your way!
Additionally, we offer the PCR test to those who are willing to wait 3-4 business days for results for a more accurate reading.
In summary, the testing situation is complicated. While we are very good at determining if you’re currently sick, there simply isn’t a good way of determining that you aren’t. And even if we do determine that you aren’t currently sick, the varying timelines between when a person contracts the virus and when they become contagious (and the possible lack of symptoms), means that testing is not a complete solution. The most important thing you can do to protect yourself and others is to continue to follow the COVID-19 best practices.