Center for Disease Control

Thursday, March 12, 2020 - 9:00am

Coronavirus Background

CDC is responding to an outbreak of respiratory disease caused by a novel (new) coronavirus that was first detected in China and which has now been detected in 60 locations internationally, including in the United States. The virus has been named “SARS-CoV-2” and the disease it causes has been named “coronavirus disease 2019” (abbreviated “COVID-19”).

On January 30, 2020, the International Health Regulations Emergency Committee of the World Health Organization declared the outbreak a “public health emergency of international concernexternal icon” (PHEIC). On January 31, 2020, Health and Human Services Secretary Alex M. Azar II declared a public health emergency (PHE) for the United States to aid the nation’s healthcare community in responding to COVID-19.

Source and Spread of the Virus

Coronaviruses are a large family of viruses that are common in people and many different species of animals, including camels, cattle, cats, and bats. Rarely, animal coronaviruses can infect people and then spread between people such as with MERS-CoV, SARS-CoV, and now with this new virus (named SARS-CoV-2).

The SARS-CoV-2 virus is a betacoronavirus, like MERS-CoV and SARS-CoV.  All three of these viruses have their origins in bats. The sequences from U.S. patients are similar to the one that China initially posted, suggesting a likely single, recent emergence of this virus from an animal reservoir.

Early on, many of the patients at the epicenter of the outbreak in Wuhan, Hubei Province, China had some link to a large seafood and live animal market, suggesting animal-to-person spread. Later, a growing number of patients reportedly did not have exposure to animal markets, indicating person-to-person spread. Person-to-person spread was subsequently reported outside Hubei and in countries outside China, including in the United States. Some international destinations now have apparent community spread with the virus that causes COVID-19, meaning some people have been infected who are not sure how or where they became infected. Learn what is known about the spread of newly emerged coronaviruses.

How COVID-19 Spreads

Current understanding about how the virus that causes coronavirus disease 2019 (COVID-19) spreads is largely based on what is known about similar coronaviruses. COVID-19 is a new disease and there is more to learn about how it spreads, the severity of illness it causes, and to what extent it may spread in the United States.

Person-to-person spread

The virus is thought to spread mainly from person-to-person.

  • Between people who are in close contact with one another (within about 6 feet).
  • Through respiratory droplets produced when an infected person coughs or sneezes.

These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.

Spread from contact with infected surfaces or objects

It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this is not thought to be the main way the virus spreads.

Can someone spread the virus without being sick?

  • People are thought to be most contagious when they are most symptomatic (the sickest).
  • Some spread might be possible before people show symptoms; there have been reports of this occurring with this new coronavirus, but this is not thought to be the main way the virus spreads.

How easily does the virus spread?

How easily a virus spreads from person-to-person can vary. Some viruses are highly contagious (spread easily), like measles, while other viruses do not spread as easily. Another factor is whether the spread is sustained. The virus that causes COVID-19 seems to be spreading easily and sustainably in the community (“community spread”) in some affected geographic areas. Community spread means people have been infected with the virus in an area, including some who are not sure how or where they became infected.

Risk Assessment

Outbreaks of novel virus infections among people are always of public health concern. The risk from these outbreaks depends on characteristics of the virus, including how well it spreads between people, the severity of resulting illness, and the medical or other measures available to control the impact of the virus (for example, vaccine or treatment medications). The fact that this disease has caused illness, including illness resulting in death, and sustained person-to-person spread is concerning. These factors meet two of the criteria of a pandemic. As community spread is detected in more and more countries, the world moves closer toward meeting the third criteria, worldwide spread of the new virus.

While there is still much to learn about the unfolding situations in California, Oregon and Washington, preliminary information raises the level of concern about the immediate threat for COVID-19 for certain communities in the United States. The potential public health threat posed by COVID-19 is very high, to the United States and globally.

At this time, however, most people in the United States will have little immediate risk of exposure to this virus. This virus is NOT currently spreading widely in the United States. However, it is important to note that current global circumstances suggest it is likely that this virus will cause a pandemic. This is a rapidly evolving situation and the risk assessment will be updated as needed.

Current risk assessment:

  • For the general American public, who are unlikely to be exposed to this virus at this time, the immediate health risk from COVID-19 is considered low.
  • People in communities where ongoing community spread with the virus that causes COVID-19 has been reported are at elevated though still relatively low risk of exposure.
  • Healthcare workers caring for patients with COVID-19 are at elevated risk of exposure.
  • Close contacts of persons with COVID-19 also are at elevated risk of exposure.
  • Travelers returning from affected international locations where community spread is occurring also are at elevated risk of exposure.

CDC has developed guidance to help in the risk assessment and management of people with potential exposures to COVID-19.

What May Happen

More cases of COVID-19 are likely to be identified in the coming days, including more cases in the United States. It’s also likely that person-to-person spread will continue to occur, including in communities in the United States. It’s likely that at some point, widespread transmission of COVID-19 in the United States will occur.

Widespread transmission of COVID-19 would translate into large numbers of people needing medical care at the same time. Schools, childcare centers, workplaces, and other places for mass gatherings may experience more absenteeism. Public health and healthcare systems may become overloaded, with elevated rates of hospitalizations and deaths. Other critical infrastructure, such as law enforcement, emergency medical services, and transportation industry may also be affected. Health care providers and hospitals may be overwhelmed. At this time, there is no vaccine to protect against COVID-19 and no medications approved to treat it. Nonpharmaceutical interventions would be the most important response strategy.

Symptoms

Reported illnesses have ranged from mild symptoms to severe illness and death for confirmed coronavirus disease 2019 (COVID-19) cases. Symptoms may appear 2-14 days after exposure*:

  • Fever
  • Cough
  • Shortness of breath

Call your healthcare professional if you develop symptoms, and have been in close contact with a person known to have COVID-19 or if you have recently traveled from an area with widespread or ongoing community spread of COVID-19.

Prevention

There is currently no vaccine to prevent coronavirus disease 2019 (COVID-19). The best way to prevent illness is to avoid being exposed to this virus. However, as a reminder, CDC always recommends everyday preventive actions to help prevent the spread of respiratory diseases, including:

  • Avoid close contact with people who are sick.
  • Avoid touching your eyes, nose, and mouth.
  • Stay home when you are sick.
  • Cover your cough or sneeze with a tissue, then throw the tissue in the trash.
  • Clean and disinfect frequently touched objects and surfaces using a regular household cleaning spray or wipe.
  • Follow CDC’s recommendations for using a facemask.
    • CDC does not recommend that people who are well wear a facemask to protect themselves from respiratory diseases, including COVID-19.
    • Facemasks should be used by people who show symptoms of COVID-19 to help prevent the spread of the disease to  others. The use of facemasks is also crucial for health workers and people who are taking care of someone in close settings (at home or in a health care facility).
  • Handwashing can help prevent illness. It involves five simple and effective steps (Wet, Lather, Scrub, Rinse, Dry) you can take to reduce the spread of diarrheal and respiratory illness so you can stay healthy. Regular handwashing, particularly before and after certain activities, is one of the best ways to remove germs, avoid getting sick, and prevent the spread of germs to others. It’s quick, it’s simple, and it can keep us all from getting sick. Handwashing is a win for everyone, except the germs. Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; and after blowing your nose, coughing, or sneezing.
    • If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol. Always wash hands with soap and water if hands are visibly dirty.

Treatment

There is no specific antiviral treatment recommended for COVID-19. People with COVID-19 should receive supportive care to help relieve symptoms. For severe cases, treatment should include care to support vital organ functions. People who think they may have been exposed to COVID-19 should contact their healthcare provider immediately.