Mainly note for myself.
My sister just found out that she was exposed to COVID-19 on Sunday evening. On Monday, she had dinner with my parents and one of my sisters. What are the chances that she could have spread it to them, having just been exposed herself?
It’s difficult to pinpoint exactly when, after exposure to COVID-19, an infected individual would become contagious. However, there’s almost no chance that one could have passed on the virus to anoother people just 24 hours after being exposed oneself.
Incubation: 2-14 ngày, đa số là 5-6 ngày.
Most contagious: 24-48hr trước khi có tr/c.
But you would still expect there to be a few days between the time a person is exposed and infected and the time they begin actively shedding virus. If we figure that infected people who become sick typically start experiencing symptoms a bit more than five days after exposure, we can calculate that infectiousness would, on average, begin rising sharply about three days post exposure. In other words, it’s safe to say that it would be exceedingly rare for anyone to transmit the virus earlier than two days post exposure; however, at some point after that, the risk would begin to rise significantly.
Evidence suggests that testing tends to be less accurate within three days of exposure, and the best time to get tested is five to seven days after you were exposed. Tests are even more accurate when patients are exhibiting symptoms. (phải có thời gian để virus sinh sôi). A study that examined false-negative rates post-exposure, found that during the four days of infection prior to symptom onset, the probability of a false negative on the PCR test went from 100 percent on Day 1 to 67 percent on Day 4. And even on the day individuals began showing symptoms, the false negative rate was still 38 percent, dropping to 20 percent three days after symptom onset. Of course, much depends on the sensitivity of the particular test being used. MIT Medical is using a test that has been shown to have a false-negative rate of less than 5 percent five days post exposure.
What are the symptoms of COVID-19?
Some people infected with the virus have no symptoms. When the virus does cause symptoms, common ones include fever, body ache, dry cough, fatigue, chills, headache, sore throat, loss of appetite, and loss of smell. In some people, COVID-19 causes more severe symptoms like high fever, severe cough, and shortness of breath, which often indicates pneumonia.
People with COVID-19 may also experience neurological symptoms, gastrointestinal (GI) symptoms, or both. These may occur with or without respiratory symptoms.
For example, COVID-19 affects brain function in some people. Specific neurological symptoms seen in people with COVID-19 include loss of smell, inability to taste, muscle weakness, tingling or numbness in the hands and feet, dizziness, confusion, delirium, seizures, and stroke.
In addition, some people have gastrointestinal (GI) symptoms, such as loss of appetite, nausea, vomiting, diarrhea, and abdominal pain or discomfort associated with COVID-19. The virus that causes COVID-19 has also been detected in stool, which reinforces the importance of hand washing after every visit to the bathroom and regularly disinfecting bathroom fixtures.
How do I know if I have COVID-19 or the regular flu?
Basically, you don’t. Just do the fucking test and doctors would also determine based on your travel history.
The FDA has granted emergency use authorization to a rapid antigen test for COVID-19. How is it different from other tests on the market?
The BinaxNOW COVID-19 Ag Card, as the test is known, detects antigen proteins on the surface of SARS-CoV-2, the virus that causes COVID-19. Unlike other diagnostic tests for COVID-19, BinaxNOW does not require a laboratory or other equipment to process or analyze the test results. This makes it portable and fast — results are available within 15 minutes.
This test is approved for use in people who are suspected of having COVID-19, and must be done within seven days of when their symptoms began. A prescription is needed to get this test, which can be performed in authorized locations including doctor's offices and emergency rooms.
Positive test results are highly specific, meaning that if you test positive you are very likely to be infected, particularly if you are tested during the first week of infection when you are experiencing symptoms. False negatives are a bigger concern. As with other antigen tests, BinaxNOW can miss infections, producing negative test results in people who are actually infected.
Still, this test could have an important role during this pandemic. It offers a quick, easy, and inexpensive way to test more people, more quickly.
What is the difference between a PCR test and an antigen test for COVID-19?
Both diagnostic tests can be used to determine whether you currently have an active coronavirus infection.
The accuracy of any diagnostic test depends on many factors, including whether the sample was collected properly, when during the course of illness the testing was done, and whether the sample was maintained in appropriate conditions while it was shipped to the laboratory. Generally speaking, PCR tests are highly accurate. However, it can take days to over a week to get the results of a PCR test.
Antigen tests detect specific proteins on the surface of the coronavirus. They are sometimes referred to as rapid diagnostic tests because it can take less than an hour to get the test results. Positive antigen test results are highly specific, meaning that if you test positive you are very likely to be infected. However, there is a higher chance of false negatives with antigen tests, which means that a negative result cannot definitively rule out an active infection. If you have a negative result on an antigen test, your doctor may order a PCR test to confirm the result.
How do saliva tests compare to nasal swab tests for diagnosing COVID-19?
The saliva test is easier to perform — spitting into a cup versus submitting to a swab — and more comfortable. Because a person can independently spit into a cup, the saliva test does not require interaction with a healthcare worker. This cuts down on the need for masks, gowns, gloves, and other protective equipment.
Either saliva or swab samples may be used for PCR tests and also for antigen tests
A systematic review and meta-analysis published in JAMA Internal Medicine found that saliva- and nasal swab-based tests that used a technique similar to PCR were similarly accurate. A positive result on either test meant that it was accurate at diagnosing the infection 99% of the time. However, approximately 16 out of 100 people who are infected will be missed.
a single negative swab or saliva test does not mean you don’t have COVID. If you have symptoms suggestive of COVID, presume you may still be infected to avoid transmitting the virus to others.
How reliable are the tests for COVID-19?
The accuracy of any diagnostic test depends on many factors, including whether the sample was collected properly. For PCR tests, which are typically analyzed in a laboratory, test results may be affected by the conditions in which the test was shipped to the laboratory.
Results may also be affected by the timing of the test. The chance of getting a false negative test result decreases if you are tested a few days after you were infected, or a few days after you develop symptoms.
Generally speaking, if a test result comes back positive, it is almost certain that the person is infected. A negative test result is less definite. There is a higher chance of false negatives with antigen tests.
If you experience COVID-like symptoms and get a negative PCR test result, there is no reason to repeat the test unless your symptoms get worse.
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