About Harvard Medical School Guides
Harvard Medical School Guides delivers compact, practical information on important health concerns. These publications are smaller in scope than our Special Health Reports, but they are written in the same clear, easy-to-understand language, and they provide the authoritative health advice you expect from Harvard Health Publishing.
- Surviving COVID-19, flu, and colds
- What causes COVID-19, flu, and colds?
- How are COVID-19, flu, and colds different?
- How to get the care you need
- Diagnosing COVID-19 and flu
- What else could it be?
- Complications of COVID-19
When Is The Best Time To Get Tested After Exposure
The CDC states that anyone who may have been exposed to someone with COVID should test five days after their exposure, or as soon as symptoms occur.
“If symptoms occur, individuals should immediately quarantine until a negative test confirms symptoms are not attributable to COVID-19,” the guidance states.
Medical experts say that even though incubation times are changing, those who test early should continue testing even if they get negative results.
How Is Someone Tested For Covid
A specialized diagnostic test must be done to confirm that a person has an active coronavirus infection. Most often a clinician takes a swab of your nose . Some tests may be done using a saliva sample. The sample is then checked for the virus’s genetic material or for specific viral proteins .
Antibody tests can tell if someone has been infected with COVID-19. But the infected person doesn’t begin producing antibodies immediately. It can take as long as three weeks for a blood antibody test to turn positive. That’s why it is not useful as a diagnostic test for someone with new symptoms.
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What Is Serologic Testing For Covid
A serologic test is a blood test that looks for antibodies created by your immune system. There are many reasons you might make antibodies, the most important of which is to help fight infections. The serologic test for COVID-19 specifically looks for antibodies against the COVID-19 virus.
Your body takes one to three weeks after you have acquired the infection to develop antibodies to this virus. For this reason, serologic tests are not sensitive enough to accurately diagnose an active COVID-19 infection, even in people with symptoms.
However, serologic tests can help identify anyone who has recovered from coronavirus. This may include people who were not initially identified as having COVID-19 because they had no symptoms, had mild symptoms, chose not to get tested, had a false-negative test, or could not get tested for any reason. Serologic tests will provide a more accurate picture of how many people have been infected with, and recovered from, coronavirus, as well as the true fatality rate.
Serologic tests may also provide information about whether people become immune to coronavirus once they’ve recovered and, if so, how long that immunity lasts.
The accuracy of serologic tests varies depending on the test and when in the course of infection the test is performed.
Test Could Not Be Read
You may have had a could not be read test result. This means its not possible to say if you had the virus when the test was done. Youll need to get another test as soon as possible.
You must continue to self-isolate if you:
- have, or develop, symptoms of coronavirus
- have been told you are a close contact by the Test and Protect service
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I’ve Heard That The Immune System Produces Different Types Of Antibodies When A Person Is Infected With The Covid
When a person gets a viral or bacterial infection, a healthy immune system makes antibodies against one or more components of the virus or bacterium.
The COVID-19 coronavirus contains ribonucleic acid surrounded by a protective layer, which has spike proteins on the outer surface that can latch on to certain human cells. Once inside the cells, the viral RNA starts to replicate and also turns on the production of proteins, both of which allow the virus to infect more cells and spread throughout the body, especially to the lungs.
While the immune system could potentially respond to different parts of the virus, it’s the spike proteins that get the most attention. Immune cells recognize the spike proteins as a foreign substance and begin producing antibodies in response.
There are two main categories of antibodies:
Binding antibodies. These antibodies can bind to either the spike protein or a different protein known as the nucleocapsid protein. Binding antibodies can be detected with blood tests starting about one week after the initial infection. If antibodies are found, it’s extremely likely that the person has been infected with the COVID-19 coronavirus. The antibody level declines over time after an infection, sometimes to an undetectable level.
Binding antibodies help fight the infection, but they might not offer protection against getting reinfected in the future. It depends on whether they are also neutralizing antibodies.
How Do Countries Plan To Use Antigen Tests
At the beginning of April, as coronavirus outbreaks raged across the world, India had tested only about 150,000 people one of the lowest testing rates per capita worldwide. On 21 August, the country conducted more than one million coronavirus tests in a single day. It reached that milestone after Indian authorities began using antigen assays to boost testing capacity.
Delhi was the first Indian state to begin using rapid antigen tests, in June. By mid-July, the number of cases there had decreased and the daily death counts had plateaued, suggesting that the tests might have played some part in controlling the spread of the virus. Epidemiologist K. Srinath Reddy, president of the Public Health Foundation of India, a non-profit organization in New Delhi, says that the Delhi example is interesting, but not clear-cut: he notes that the government started to lift lockdown restrictions in August, which led to a surge in infections. Rapid antigen tests have picked up the increased number of cases, but whether they have been successful in limiting the spread of COVID, well only know in the next couple of months, Reddy says.
A testing centre at the international airport in Rome. Italy plans to use rapid antigen tests to screen passengers at all of its airports.Credit: Simona Granati/Corbis/Getty
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You Can Order A Pcr Test Kit To Be Sent To Your Home Or Book An Appointment At A Walk
Almost into the pandemic, most of us have taken out fair share of Covid tests.
Omicron is a game changer, and PCR tests are vital to stemming the spread.
Heres everything you need to know about PCR tests.
What Tests Are There And How Do They Work
Tests for COVID-19 fall into two categories: diagnostic tests such as PCR and antigen assays, which detect parts of the SARS-CoV-2 virus, and antibody tests that sense molecules that people produce when they have been infected by the virus. Antibodies can take several days to develop after an infection and often stay in the blood for weeks after recovery, so antibody tests have limited use in diagnosis .
The high-sensitivity PCR tests are almost 100% accurate in spotting infected people, when they are administered properly. But such tests generally require trained personnel, specific reagents and expensive machines that take hours to provide results.
Countries such as South Korea and New Zealand have succeeded in boosting PCR-based testing, but scaling up these tests has proved difficult elsewhere. The United States, for example, has seen a slow and poorly coordinated response to outbreaks, faulty tests from the Centers for Disease Control and Prevention and problems with the supply chain. All of this has hindered efforts to collect and process samples for PCR, pushing waiting times to days or even weeks. These delays, along with a lack of tests, have contributed to the rampant spread of COVID-19 across the country, which by 16 September had seen almost 200,000 deaths from the disease.
A technician in a mobile unit conducts rapid antigen tests for COVID-19 in New Delhi.Credit: Mayank Makhija/NurPhoto via Getty
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How You May Be Able To Get Covid
Senior Wellness & Travel Editor, HuffPost
The most painful thing about taking a COVID-19 test isnt necessarily the swab that practically extends to your brain . Its the painstaking amount of time it takes to get the results back.
There are a few main reasons why lab results take so long, according to experts. First and foremost is the sheer number of people getting tests.
As COVID-19 cases have surged in many areas of the United States, so too has the number of people requesting tests, said Kristin Dean, the associate medical director at Doctor on Demand.
The rising demand has so far outweighed the number of labs and health care workers who able to process the results in a timely manner.
There are still a finite number of labs and analyzers in existing labs that have the capability to the analyze a COVID-19 test sample, said Karen Smith, system vice president of laboratory services at CommonSpirit Health.
Efforts are underway nationwide to stand up more lab capacity and to procure more test platforms and reagents, which will help meet the demand and need for quick results in the coming weeks, she continued. COVID-19 is going to be with us for the foreseeable future and our country needs to invest in developing new labs and other testing capabilities.
The process of transporting samples from testing sites and doctors offices to offsite labs can also cause slower results.
But with that in mind, here are some ways you might be able to get your lab work faster.
Video: What To Know About Covid
Companies continue to develop new ways to test for SARS-CoV-2, the virus that causes COVID-19. One thing is clear, though: We need scalable testing options with fast results. As businesses reopen and students return to in-person classes, infections need to be quickly identified to prevent further spread.
This is now possible, thanks to the emergence of rapid testing options for the virus that causes COVID-19. Several companies have developed tests that can be done at point-of-care, such as at a clinic or healthcare providers office. With these tests, samples dont need to be sent to a laboratory for processing. Most of these rapid tests can produce results in 30 minutes or less.
In this article, well cover the basics of rapid diagnostic tests and the best way to find one near you.
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Look For Locations That Offer Rapid Tests
Chances are youll get a swab up your nose when being tested for COVID-19 test aka a PCR test.
PCR testing is the most common and reliable way to detect COVID-19, but there are some other options if you desperately need results sooner, Dean said.
There are also alternative testing types to the PCR testing, these rapid tests can provide results same day, she said.
However, she added that, It is important to caution that early rapid tests were not as reliable in terms of ruling out an active COVID-19 infection meaning that rapid tests are more likely to produce false or inconclusive results.
Dean recommended researching your city and rapid COVID-19 testing to see if a location near you offers these tests. Your city or state should also have a website where you can find testing centers, which may indicate if they have rapid tests or not.
What Does It Mean If I Test Negative For Covid
A negative test result means that the virus that causes COVID-19 was not found in your sample. However, it is possible for this test to give a negative result that is incorrect in some people with COVID- 19. You might test negative if the sample was collected early during your infection.
You could also be exposed to COVID-19 after your sample was collected and then have become infected. In particular, people infected with COVID-19 but who have no symptoms may not shed enough virus to trigger a positive test. This means that you could possibly still have COVID-19 even though the test result is negative.
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I wouldnt trust tests that are done on consecutive days if ones positive and ones negative. But say someones infected and theyre getting better at five days, and they have another home antigen test and thats negative, that person can then go and be around others with very little risk of transmission.
-Dr. Joseph Kontra, chief of infectious diseases, Penn Medicine Lancaster General Health
If You’ve Been In Close Contact With Someone Who’s Tested Positive
If you’ve been in close contact with someone who’s tested positive for COVID-19 and youre:
- fully vaccinated , or aged between 5 years and 18 years and 6 months old, you should do daily rapid tests . You do not need to isolate if your tests show a negative result. If you test positive you should self-isolate immediately. Find out more about daily testing on GOV.UK
- not fully vaccinated, get a PCR test and stay at home and self-isolate for 10 days even if your PCR is negative.
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What Is A Pcr Covid Test
PCR tests are the gold standard and are sent off to a lab to be properly processed – unlike lateral flow tests that can be completed at home in less than an hour.
PCR swabs can be taken at a drive-through centre or can be sent to you at home.
It is sent to a laboratory where a lab technician looks for genetic material of the virus using highly specialised equipment.
The PCR tests are much better at finding very small amounts of the virus, especially early during an infection.
So these are used primarily in people who have Covid symptoms.
Public Health Surveillance Testing For Sars
Public health surveillance is the ongoing, systematic collection, analysis, and interpretation of health-related data essential to the planning, implementation, and evaluation of public health practice. See CDCs Introduction to Public Health Surveillance.
Public health surveillance testing is intended to monitor community- or population-level outbreaks of disease or to characterize the incidence and prevalence of disease. Surveillance testing is performed on de-identified specimens, and, thus, results are not linked to individual people. Public health surveillance testing results cannot be used for individual decision-making.
Public health surveillance testing may sample a certain percentage of a specific population to monitor for increasing or decreasing prevalence or to determine the population effect from community interventions, such as social distancing. An example of public health surveillance testing is when a state public health department develops a plan to randomly select and sample a percentage of all people in a city on a rolling basis to assess local infection rates and trends.
CDC is working with state, local, territorial, academic, and commercial partners to conduct surveillance to better understand COVID-19 in the United States and recently conducted a multistate assessment of SARS-CoV-2 seroprevalence in blood donors.
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Cleaning And Safety Standards
We understand that going to a testing location may be stressful. Please know that all testing locations, whether they are testing people with symptoms or without symptoms, have very high cleaning and safety standards to make sure the virus does not spread. Testing locations must implement and follow infection prevention and control measures in compliance with the provincial testing guidance to protect Ontarians against COVID-19covid 19.
The testing location staff will:
- require appointments for in-store testing at participating pharmacies
- wear the appropriate personal protective equipment
- organize a dedicated space to perform testing
- routinely disinfect the testing area using the highest-quality cleaning products
- make sure everyone is physically distancing and wearing masks
Living With Someone Waiting For Their Result
Restrict your movements if you live with someone that has symptoms of COVID-19 and is waiting on a test result. But you do not need to do this if you have completed your first round of COVID-19 vaccination, had a booster, or had a positive PCR test in the past and do not have symptoms – unless advised to by a public health doctor.
If their test comes back positive, you will be a close contact and should follow the advice for close contacts.
If their test comes back negative, you can return to your normal activities.
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Q: How Long After Contracting Covid
If your friend had severe disease, meaning they ended up in the hospital or ended up needing oxygen, youre advised to wait 20 days* before theyre not infectious, before youd be safe to hang out with them. If you had mild disease provided youre getting better, provided you have no fever, without a test, 10 days, and with a test, you can test on day five, and if the antigen test or the PCR is negative, youre safe, youre considered to be non-infectious.
The issue is, one, the PCR often stays positive for 30 days, and Ive seen it stay positive for months. And twofor example, if I had to hang out with an elderly parent or someone who is at risk, I wouldnt do it before day 10 without a negative antigen test, and I probably would wait till day 10 if the other person, if they got COVID, were at risk of getting very sick.
So severe disease 20 days. Mild disease, no testing 10 days. Mild disease with a negative antigen test at day five, you can go back to work.
*This is the number of days after developing symptoms
-Dr. John Goldman, infectious disease specialist, UPMC