This story is a summary of the information you need to understand Covid-19 and how it affects you. It is accumulated from multiple sources as a means of fact checking.


  • Wear a mask, anything is better than nothing
  • Immunity is not necessarily guaranteed
  • Rapid Tests indicate most contagious
  • Be wary of long-term effects

Prevention and Detection

The human Covid-19 is primarily spread by person-to-person contact through respiratory droplets generated by breathing, sneezing, coughing, etc (see La Rosa et al. 2020 and ECDC). This is why masks are a useful tool in preventing spread and why testing involves extraction of fluids from the nose and/or throat.


Despite the ongoing discussion that masks do not really help, research shows that masks cut down the chances of both transmitting and catching Covid-19, even if it is just to reduce the amount of viral dose that you are exposed to (see Nature, Ghandi et al. 2020). While the virus particle is very small, it is actually transported via “pathogen-transporting droplets and aerosols”, which are larger. These larger particles spread especially when people are talking (See New England Journal of Medicine). Therefore, there is a variety of DIY masks that are able to block those transported virus particles. Therefore, there is no reason not to wear something, even if it is a cotton shirt, around your nose and mouth when near other people.

There are many different DIY masks that provide a range of different protections. Researchers from Colorado State University have created an informative dashboard to compare different DIY masks and their effectiveness if you would like to make your own comparisons. According to their dashboard, a 2-layer bandana is on average the least effective for the full-range of particle sizes. Several sources also show that the neck gaiter is one of the least effective options (see Fischer et al. 2020). The best masks use a form of filter and/or multiple layers of materials. However, almost all are protective against larger particle sizes.

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Images from Fischer, E. P., Fischer, M. C., Grass, D., Henrion, I., Warren, W. S., & Westman, E. (2020). Low-cost measurement of face mask efficacy for filtering expelled droplets during speech. Science Advances, 6(36).

In summary, WEAR SOME KIND OF MASK! The more layers and the tighter the weave the better… (see Khonda et al. 2020).

Optional Note: The reason that the CDC and the WHO recommended not purchasing masks at the start of the pandemic was due to the low supply available for medical professionals, who needed to be prioritized (see Nina Bai, UCSF 2020 and Nature). Most of the research showing masks as ineffective have been retracted or called for retraction (see Stanford Letter).


There are two forms of tests that are commonly used to detect an ongoing infection of Covid-19: PCR and Rapid Test.

PCR is a genetic based test looking for genetic material of the virus in the system. These tests are more sensitive and therefore are able to catch Covid-19 with less presence of the viral material. They are more accurate but take longer to receive the results. Although this test is able to determine if you are positive, you may receive a positive result and not be infectious to others (see Nature).

Optional Note: These tests were the original test provided by the CDC in the first roll-outs of testing. Early on, there were issues with contamination resulting in unreliable results (see Technology Review, CDC, NY Times). This is why you may have heard that the tests are extremely unreliable, but this issue has been resolved and more organizations have been able to create their own PCR tests in addition to the CDC.

Rapid Test is an antigen based test. These tests are less sensitive, making them prone to false negatives for the presence of the virus in the system. This means that if you receive a positive result from a rapid antigen test, it means there is a large amount of the virus in your system and you are more infectious to others at that time. In other words, positive means infectious! While negative means you may have Covid-19, but you are less infectious to others. These tests are also quick, you will get your results within 15–20 minutes.

Optional Note: These tests are increasingly being used because of the research showing how useful they are for finding the most contagious individuals. According to a scientific article, individuals are unlikely to spread the virus about eight to ten days after showing symptoms (SeeHe, X. et al. Nature Med. 2020 and Larremore, D. B. et al. Preprint at medRxiv 2020). These are the days that a PCR test would detect Covid while a Rapid Test will most likely not. However, this still does not guarantee you are NOT contagious, so please follow all guidelines from your medical professionals.

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From Nature by Giorgia Guglielmi (September 16, 2020)

The above summarizes the major differences between the two tests (ignore the antibody test for now). As you can see in the image, the red line depicts the rapid test and returns positive only for a short period of Covid-19 infection, while PCR is able to detect for a much longer period of time.


There are a variety of symptoms related to Covid-19, some even long term. They can often be confused with other conditions such as allergies or gastrointestinal issues like GERD. It is important to be vigilant with testing and preventative measures to ensure you avoid Covid-19. An example of the potential overlap in symptoms is shown in the following image comparing Covid-19 to allergies:

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Image from the CDC.

Acute Symptoms

The variety of reported symptoms are primarily from individuals who have been hospitalized, meaning they are experiencing a severe case of Covid-19. This means take the following lightly as you may experience much milder symptoms then the following reported, or maybe none at all, but can still infect others.

Three clusters of symptoms were found in a study from acute care hospitals in England, Wales and Scotland.

  • The first cluster is respiratory based, with cough, sputum, shortness of breath, and fever.
  • The second cluster is musculoskeletal based with muscle aches, joint pain, headache, and fatigue.
  • The third cluster is gastrointestinal based with abdominal pain, vomiting, and diarrhea.

Several studies found the most common symptoms were cough, shortness of breath and nasal obstruction (see Lechien et al 2020, ISARIC 2020, Zhang et al. 2020). In addition to these, changes in smell and taste have been found common in acute cases (see Tong et al. 2020 and Aziz et al. 2020).


Current research by Buitrago-Garcia et al. in PLOS Medicince found that approximately 20% of individuals infected with Covid-19 do not experience any symptoms during infection (see Healthline for a summary). There are many cases where individuals start with no symptoms, but later develop symptoms. However, it is important to note that asymptomatic individuals are still able to spread the virus to others (see Meyer et al. 2020 and Healthline).


This term was actually new to me at the start. It means that during infection one may not experience symptoms while contagious to others but later develop symptoms. Therefore they are able to infect others when they feel no symptoms but will experience symptoms after they may have already infected people (see Health). The PLOS Medicine study found “a higher proportion of all SARS-CoV-2 infections resulting from transmission from presymptomatic individuals than from asymptomatic individuals.” (Buitrago-Garcia et al., 2020). One study they found that symptoms appeared a week later after the initial positive test while experiencing no symptoms (see CDC). They found that “the mean interval from testing to symptom onset in the presymptomatic residents was 3 days” (Kimball A, Hatfield KM, Arons M, et al., 2020). This is why the CDC states that symptoms can begin 2–14 days after infection.


Long-Term Effects

According to multiple sources, it is possible to experience long-term effects for both symptomatic and asymptomatic infections (see Cella et al., 2020 and MayoClinic).

Specific to both acute and mild infections, two groups were defined: ones that experience symptoms for more than three weeks called post-acute Covid-19 and those that experience symptoms beyond 12 weeks called chronic Covid-19 (see BMJ 2020). Most preliminary studies are finding that many of our organs are affected during infection, including the heart, kidneys and the digestive and nervous systems (see WSJ 2020).

Cardiovascular issues have been frequently mentioned as a prolonged symptom. While the acute list of symptoms does not often include cardiovascular related issues, long-term related symptoms often do. Although individuals with pre-existing cardiovascular issues are more likely to experience this, young active individuals have also reported such long-term symptoms (see BMJ 2020, WSJ 2020, Puntmann et al. 2020, CDC 2020 and WSJ 2020). 1 in 5 young, healthy individuals reported prolonged symptoms (see WHO 2020).

Digestive issues have also been mentioned in several researchers’ findings (see WSJ 2020, Ng et al. 2020 and Lamers et al. 2020).

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Image is from Greenhalgh, T., Knight, M., Buxton, M., & Husain, L. (2020). Management of post-acute covid-19 in primary care. bmj, 370.

A more comprehensive list of long-term symptoms are:

  • Fatigue
  • Cough, congestion or shortness of breath
  • Loss of taste or smell
  • Headache, body aches
  • Diarrhea, nausea
  • Chest or abdominal pain
  • Confusion
  • heart palpitations
  • the new onset of diabetes or high blood pressure

(See Medical News Daily and Tenforde et al., CDC, 2020)

The below figure from a USA based study shows the initial symptoms of Covid for a subset of patients in light blue and prolonged symptoms in dark blue.

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From Tenforde MW, Kim SS, Lindsell CJ, et al. Symptom Duration and Risk Factors for Delayed Return to Usual Health Among Outpatients with COVID-19 in a Multistate Health Care Systems Network — United States, March–June 2020. MMWR Morb Mortal Wkly Rep 2020;69:993–998. DOI: icon.


What about immunity you might ask? Well, there are not enough studies yet to confidently answer this. The safest thing to do is therefore continue to wear masks until a vaccine is readily available or more research is published on this particular topic.

This is what we know so far.

The main challenge is understanding whether individuals are experiencing re-infection of the virus or a continuation of the initial infection. According to Nature, researchers from Hong Kong and Nevada found evidence that re-infection is possible, but how likely and frequent this occurs is still unknown. One study found that individuals had protective anti-bodies for 5–7 months after onset (Ripperger et al, Immunity, 2020 and Healthline). Others studies show a smaller lifespan (Wang et al., 2020).

What else do you want to know?

If you would like me to cover any further areas related to Covid-19, feel free to leave suggestions!

More Resources

PhD Student in the UCF Center for Research in Computer Vision

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