Updated on September 4, 2024.
Since the first COVID infections were reported in late 2019, the disease has continued to affect people around the world—physically, emotionally, and financially. During the first years of the pandemic, people radically changed their social habits, work environments, and health practices. Meanwhile, researchers, clinicians, government leaders, pharmaceutical companies, and other organizations and industries stepped up to meet the global crisis by creating and delivering multiple safe and effective vaccines.
With the initial shock and the deepest throes of the pandemic over now, it’s possible to step back and take stock of this global crisis. While we know much more about COVID than we did in late 2019, there is more to learn and understand.
The origins of COVID-19
The coronavirus that causes COVID-19 was reported to the World Health Organization (WHO) on December 31, 2019, after doctors in Wuhan, China, noticed a cluster of mysterious cases of pneumonia for which they didn’t know the cause. A little more than a month later, the WHO declared the illness caused by the newly identified virus SARS-CoV-2 to be a Public Health Emergency of International Concern.
SARS-CoV-2 is just one of seven coronaviruses known to infect humans. Four of them cause mild infections like the common cold, but three have led to serious illnesses. These include Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS).
Coronaviruses derive their name from the Latin word corona, for crown. They are so identified for their characteristic spikes that resemble a crown. These viruses usually circulate among animals, particularly camels, bats, and cats. On rare occasions, animal coronaviruses can mutate and spread to people.
There are two main theories for how SARS-CoV-2 spread to humans, both of which are plausible.
The first is that there was a laboratory accident in China that allowed the virus to escape. The other theory is that the virus leapt from animals into humans at the Huanan market in Wuhan, in a process known as natural zoonotic spillover.
The spillover theory was the one preferred by most experts in a February 2024 survey led by the nonpartisan think tank Global Catastrophe Risk Institute. That said, the origin story of COVID is still very much debated among scientists and politicians.
COVID symptoms to understand
People infected with COVID can experience no symptoms or they can develop any of a range of symptoms. These usually start between two and 14 days after being exposed to the virus.
Symptoms can change according to one’s vaccination status or which COVID variant a person is infected with. The most common symptoms include:
- Fever or chills
- Cough
- Shortness of breath
- Sore throat
- Runny nose or congestion
- New loss of smell or taste
- Fatigue
- Headache
- Muscle and body aches
- Nausea, vomiting, or diarrhea
Emergency signs of COVID-19 include:
- Difficulty breathing
- Persistent pain or pressure in the chest
- Feeling suddenly confused
- Trouble waking up or staying awake
- Discolored lips, nail beds, or skin. (Depending on skin tone, a person with a severe case of COVID may look pale, blue, or gray.)
If you or someone you know is displaying any of these serious symptoms, seek immediate medical attention by calling 911 or going directly to the emergency department at the nearest hospital.
Some people with COVID are at higher risk of severe illness
Anyone can develop COVID, but some people are more at risk of severe symptoms, hospitalization, or even death. These include:
- People older than 65
- Those with a weakened immune system
- People with other chronic conditions, such as cancer, kidney disease, lung disease, diabetes, heart conditions, serious mental illness, and overweight and obesity
- People affected by socioeconomic disparities, including people from racial and ethnic minority groups
- People with disabilities
- People who are physically inactive
- Pregnant people
- People who smoke and those with substance use disorders
COVID can also affect children and teens who have other medical conditions, especially if they’re medically complex, or have to do with genetic, neurological, or metabolic conditions.
How the infection spreads
COVID is highly contagious. The infection spreads mainly through contaminated respiratory droplets or small particles that are emitted when infected people cough, sneeze, breathe, speak, or sing. When these droplets and small particles escape the body, they may be breathed in by other people, or land in a nearby person’s mouth, nose, or eyes.
If droplets land on a contaminated surface that you touch and then touch your mouth, nose, or eyes, you can also become infected, though this is less common than airborne transmission.
Diagnosing COVID
There are two categories of tests used to diagnose COVID infection: diagnostic tests and antibody tests.
Diagnostic tests
The two main types of diagnostic tests are:
- Nucleic acid amplification tests (NAATs), which are usually referred to by one particular type, the polymerase chain reaction (PCR) test
- Antigen tests
Both of these tests check for the coronavirus itself, using a respiratory sample collected with a nasal or throat swab. The results reveal whether or not you’re currently infected. PCR tests are typically quite accurate, but they can take hours or days to process and yield results.
Antigen tests are designed to detect fragments of proteins found on or inside the virus. Antigen tests are much quicker, providing results within 15 to 30 minutes. Although positive antigen test results are very reliable, these tests tend to miss more cases than PCR tests. That means that a negative antigen test may need to be confirmed with a PCR test or by taking a second and even a third antigen test, with each test taken two days apart.
Antibody tests
Antibody tests are another type. Unlike a diagnostic test, an antibody test doesn’t tell you if you have the disease right now. It helps determine if you’ve been infected in the past. And rather than testing respiratory specimens collected by swabs, antibody tests (also called serology tests) check your blood for antibodies to SARS-CoV-2, which would indicate a past encounter with the virus.
Recovery doesn’t guarantee immunity
After recovering from COVID, you will likely be immune for some weeks or even months, but this protection wanes rapidly over time. You can still get sick again, particularly from a different variant of the virus.
Being vaccinated and keeping up-to-date with COVID-19 vaccinations is the best way to maintain a high level of immunity. You may still develop a case of COVID, but your risk of severe illness will be lowered, your symptoms will likely be milder, and you will be less likely to develop long COVID. And if you have had an infection plus vaccination, you’ll have what’s known as hybrid immunity, which is the strongest type.
Understanding long COVID
Even after recovering from a COVID infection, some people experience symptoms that last for weeks, months, or even years. These can include any of more than 200 symptoms, but the most common symptoms include:
- Problems with smell and taste
- Fatigue
- Headaches
- Difficulty with concentration and memory
- Gastrointestinal issues
- Post-exertional malaise (exhaustion after being physically or cognitively active)
- Difficulties with sleep
- Cough and shortness of breath
- Fast heart rate and lightheadedness
The causes of long COVID may be quite complex, but may include:
- Problems from excessive inflammation
- Tiny clots in small blood vessels (called micro clots)
- The virus persisting in one area of the body after clearing from the rest of the body
- An outsized response from the immune system
Treating COVID
In most cases, people with mild or moderate COVID and who are at low risk for complications can manage their symptoms and recover at home. Supportive care can help. This includes using over-the-counter pain relievers, getting plenty of rest, and drinking fluids.
People with mild to moderate symptoms who are at high risk for complications may be eligible to be treated with antiviral drugs like nirmatrelvir with ritonavir (Paxlovid) or molnupiravir (Lagevrio). These are pills that can be taken as many as five days after your first symptoms appeared, though the sooner the better.
Remdesiver (Veklury) is an antiviral drug given by infusion through the blood. It can be taken as many as seven days after the first symptoms showed up.
Preventing COVID
One of the best ways to protect yourself against COVID is to be vaccinated and to stay up-to-date on the latest vaccines produced by Pfizer-BioNTech, Moderna, or Novavax. Vaccines are safe and very effective at preventing severe illness.
The Centers for Disease Control and Prevention (CDC) recommends that everyone ages 6 months and older should receive the latest vaccine. How many shots you should get and the timetable for getting vaccinated may vary depending on your age, previous vaccination status, which vaccine you previously received, and whether you are moderately or severely immunocompromised.
For people who are at high risk of getting severely ill from COVID, a preventive monoclonal antibody called pemivibart (Pemgarda) can be prescribed by a healthcare provider (HCP) in addition to vaccination. This medication contains lab-made molecules that can imitate the natural antibodies in the immune system to offer extra protection against illness.
How to protect yourself and others
If you test positive for COVID, you should isolate yourself as much as possible. For the next five days, wear a snug-fitting mask when you’re around others. Opt for masks that have a good seal around your face but that are still comfortable. Filtering facepiece respirators (FFRs) approved by the National Institute for Occupational Safety and Health (NIOSH) are good options. These include N95 masks. International FFRs like KN95 masks fall into this category, though they aren’t NIOSH-approved.
Other ways to help prevent the spread of COVID-19 include:
- Ventilation: Ensure good ventilation at home or at work by opening windows and using fans, air purifiers, high-efficiency particular air (HEPA) cleaners, and filters for your heating, ventilation, and air conditioning (HVAC) system.
- Hygiene: Practice good hygiene. This includes washing or sanitizing your hands, covering your sneezes and coughs, and disinfecting any surfaces that you touch often. Avoid touching any part of your face, including your eyes, nose, or mouth, with unwashed hands.
- Following the news: Keep abreast of when there is a rise in COVID infections in your community and take steps to protect yourself and others by wearing a mask in public or crowded places and meeting with others outdoors when possible.
