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Coronavirus disease 2019 (COVID-19) is the official name given by the World Health Organization (WHO) to the disease caused by SARS-CoV-2, the new coronavirus that surfaced in Wuhan, China in 2019 and spread around the globe. By March 2020, COVID-19 was so widespread that the WHO characterized it as a global pandemic, a disease outbreak that covers a wide geographic area and affects an exceptionally high proportion of people.

People who have been infected with COVID-19 respond in different ways—some report mild symptoms or no symptoms at all. Others experience severe symptoms, are hospitalized, and even die from the disease.

Efforts to mitigate the disease have included “social distancing,” masks, and stay-at-home mandates. By early 2021, scientists had developed effective vaccines, and countries around the globe were focused on quickly vaccinating as many people as possible. But there was more to learn, especially with the identification of new SARS-CoV-2 variants (new strains based on mutations in the sequence of the genetic code of the original virus). Meanwhile approaches to treating the disease are still evolving.

From where did COVID-19 originate?

The coronavirus SARS-CoV-2 was never seen before it surfaced in December 2019—when it was believed to have passed somehow from an animal to a human at a large seafood and live animal market in Wuhan. It is one of seven known coronaviruses that cause illnesses that range from the common cold to severe acute respiratory syndrome (SARS), an epidemic that killed almost 800 people in 2002 and 2003.

COVID-19 is the first pandemic known to be caused by the emergence of a new coronavirus—novel influenza viruses caused four pandemics in the last century (which is why some of the response to the new disease has been adapted from existing guidance developed in anticipation of an influenza pandemic). 

How does COVID-19 spread?

The disease is believed to spread easily among people in the following ways, according to the CDC:

  • Through respiratory droplets transmitted in small particles when a person who is infected coughs, talks, or sneezes. These droplets can land in the mouths or noses of bystanders, who possibly inhale them into the lungs.
  • Between people who are within 6 feet (2 arm lengths) of each other. There is evidence that droplets can stay suspended in the air and travel beyond 6 feet when someone coughs, sneezes, sings, or even breathes. For this reason, indoor environments without good ventilation (including gyms, restaurants, and churches) are considered risky.
  • By touching a surface or object where droplets have landed, and then touching the eyes, nose, or mouth. But experts don’t believe this is the main way the virus spreads.

What are the symptoms of COVID-19?

The CDC believes COVID-19 is most contagious when people who have it are most symptomatic (although asymptomatic people can spread it as well). Symptoms of COVID-19 can appear anytime between two and 14 days after exposure. Most people report one or more of the following symptoms over the course of their disease:

  • Fever or chills
  • Cough
  • Shortness of breath and difficulty breathing
  • Fatigue
  • Muscle or body aches
  • Headache
  • New loss of taste or smell
  • Congestion or runny nose
  • Nausea or vomiting
  • Diarrhea

You should call your medical provider for advice if you have been in close contact with a person known to have COVID-19 or if you live in an area with ongoing spread of the disease and notice these symptoms.

Seek medical attention immediately if you experience emergency warning signs, including difficulty breathing or shortness of breath, persistent pain or pressure in the chest, new confusion or ability to arouse, or bluish lips or face. This list is not inclusive, so consult your medical provider if you notice other concerning symptoms. 

Who is at risk for COVID-19 and complications from the disease?

Anyone who may have been exposed to the SARS-CoV-2 is at risk for COVID-19. Experts are still learning about how to predict who will develop severe symptoms that could lead to hospitalization, time in an intensive care unit, or use of a ventilator to help with breathing.

But the risk for complications does appear to increase with age—people in their 50s are at higher risk for complications than those in their 40s, people in their 60s have more risk than those in their 50s, and people who are 85 and older are at the highest risk, according to the CDC, which reports that 8 out of 10 deaths from COVID-19 have been reported in people aged 65 and older.

Adults of all ages with medical conditions are at higher risk for complications, as are people who smoke. The list of conditions includes, but is not limited to, cancer, heart conditions, obesity, pregnancy, and type-2 diabetes mellitus. 

Fewer children than adults have gotten sick with COVID-19, but there have been cases where children have gotten severely ill. Doctors are concerned about a rare condition called multisystem inflammatory syndrome (MIS-C) in children, which can cause dangerous inflammation levels throughout the body. While more information is needed, medical experts believe MIS-C is related to COVID-19.

How is COVID-19 treated?

Researchers continue to study the safety and effectiveness of a number of treatments for COVID-19. Many treatments are still in the early stages of research and some have shown promise, but scientists need more data on their safety and effectiveness.

The FDA has given approval for only one drug, called remdesivir, and emergency use authorizations (EUAs) for a handful of others. While remdesivir has not been shown to reduce mortality from COVID-19, there is evidence that shows it may shorten time spent in the hospital, and it’s recommended for use in hospitalized patients age 12 and older. A corticosteroid (or steroid) called dexamethasone has shown promise for its ability to reduce deaths in seriously ill patients. The National Institutes of Health is recommending it for those who are on oxygen or ventilators.

Some supportive treatments have also helped, including prone positioning, which is simply having patients lie face down to open up their lungs. Doctors in the hospital also provide noninvasive oxygen or use ventilators to support seriously ill patients with COVID-19. 

What vaccines are available in the U.S.?

In December 2020, the FDA granted emergency use authorization to two vaccines, one from Pfizer-BioNTech and one from Moderna. Both are two-dose mRNA vaccines that work by injecting genetic material into the body to create a protein from the virus so the immune system will recognize the virus and attack it. In February 2021, the FDA granted emergency use approval for a different type of vaccine, called a carrier, or virus vector, vaccine by Johnson & Johnson. 

In the U.S., the CDC makes recommendations for who should get the vaccine first, but each state makes its own plan. The CDC website provides information on how to look up each state’s vaccination plan. (Information on where to get the vaccine, including which sites have doses available, will gradually become available through a CDC tool called VaccineFinder.)

How effective are vaccines against COVID-19?

The Pfizer-BioNTech and Moderna vaccines were shown in clinical trials to have an overall efficacy of 95% and 94.1%, respectively. The Johnson & Johnson vaccine was shown to have an overall efficacy of 72% and 86% efficacy against severe disease in the U.S.  

Researchers continue to work on developing new vaccines. Governments around the world are working quickly to vaccinate as many people as possible using vaccines they have already authorized for use against COVID-19. Meanwhile, new mutations of the virus are emerging that could be more contagious and likely to cause more severe disease, and work is being done to tweak the vaccines to provide more protection.

What other precautions can I take to avoid COVID-19?

The CDC recommends the following preventive actions:

  • Wash your hands often with soap and water for at least 20 seconds, especially if you have been in a public place. If soap isn’t available, use a hand sanitizer with at least 60% alcohol.
  • Avoid close contact with those who are sick.
  • Practice social distancing by staying at least 6 feet (about 2 arms’ lengths) away from other people. Remember that some people may be able to spread the virus even though they don’t have symptoms.
  • Cover your mouth and nose when you are around others.
  • Wear a cloth face mask when around people who don’t live in your household and in public settings where other social distancing measures are difficult to maintain, especially in areas where there is significant community transmission. But remember that a mask is not a substitute for social distancing. The CDC recommends a high-quality mask that fits well and has multiple layers of fabric, or doubling up on masks by wearing one disposable mask beneath a cloth mask.
  • Use a tissue to cover your mouth and nose when you cough or sneeze.
  • Use a household wipe or spray to clean and disinfect doorknobs, light switches, desks, keyboards, sinks, and other objects and surfaces that are frequently touched.
  • Monitor your health every day. Be alert for COVID-19 symptoms and check your temperature if symptoms develop.

Will a flu shot protect against developing a severe case of COVID-19?

While a flu shot won’t prevent or reduce severity of COVID-19, public health authorities strongly advise everyone to get their annual flu shot. In addition to preventing or mitigating the severity of flu, the vaccine may simplify the evaluation of patients during the flu season who may have a more serious condition.  

How is Yale Medicine prepared to handle patients with COVID-19?

Yale Medicine Infectious Diseases has an entire team with experience treating both existing and emerging diseases. This team is at the forefront of the latest testing, diagnostic, and treatment approaches.

The Yale Medicine Winchester Center for Lung Disease’s Post-COVID-19 Recovery Program offers pulmonary-focused, multidisciplinary evaluation and care for patients recovering from COVID-19. The program partners with teams taking care of patients in the hospital, as well as community providers to identify patients who have persistent symptoms or appear at risk of developing post-COVID-19 complications.

Yale New Haven Health offers a call center for patients and people in the community who have questions about COVID-19 at 833-ASK-YNHH (833-275-9644).