How the Corona Virus Spreads

Coronavirus Spread – how Does it Happen?

What began with a handful of mysterious illnesses in a vast central China city has travelled the world, jumping from animals to humans and from obscurity to international headlines. First detected on the last day of 2019, the novel coronavirus has infected tens of thousands of people — within China's borders and beyond them — and has killed more than 15,000. It has triggered unprecedented quarantines, stock market upheaval and dangerous conspiracy theories.

Most cases are mild, but health officials say the virus's spread through the United States appears inevitable. As the country and its healthcare system prepare, much is still unknown about the virus that causes the disease now named COVID-19.

The Washington Post has spoken to scores of doctors, officials and experts to answer as many of your questions as we can about the newest global health emergency.

As many as 25 per cent of people infected with the new coronavirus may not show symptoms, the director of the Centers for Disease Control and Prevention warns — a startlingly high number that complicates efforts to predict the pandemic's course and strategies to mitigate its spread.

In particular, the high level of symptom-free cases is leading the C.D.C to consider broadening its guidelines on who should wear masks.

"This helps explain how rapidly this virus continues to spread across the country," the director, Dr Robert Redfield, told a National Public Radio affiliate in Atlanta in an interview broadcast on Monday.

Like many others, you probably have questions about the 2019 coronavirus. And one of those questions may have to do with how the virus can spread.

First, some brief explanation about the coronavirus itself: The clinical name for this novel coronavirus is SARS-CoV-2. It stands for severe acute respiratory syndrome coronavirus 2.

It originated from a family of other virusesTrusted Source that causes respiratory diseases like severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome (MERS).

Because the novel coronavirus is a new strain, it's unfamiliar to our immune systems. And there's not yet a vaccine for it.

Coronaviruses are a family of viruses that cause disease in animals. Seven, including the new virus, have made the jump to humans, but most just cause cold-like symptoms.

COVID-19 is closely related to severe acute respiratory syndrome (Sars), which swept around the world from 2002 to 2003. That virus infected around 8,000 people and killed about 800 but it soon ran itself out, mainly because most of those affected were seriously ill so it was easier to control.

Another coronavirus is Middle East respiratory syndrome (Mers), cases of which have been occurring sporadically since it first emerged in 2012 - there have been around 2,500 cases and nearly 900 deaths. 

COVID-19 is different from these two other coronaviruses in that the spectrum of disease is broad, with around 80 per cent of cases leading to a mild infection. There may also be many people carrying the virus and displaying no symptoms, making it even harder to control. 

So far, around 20 per cent of COVID-19 cases have been classed as "severe", and the current death rate varies between 0.7 per cent and 3.4 per cent depending on the location and, crucially, access to good hospital care.

COVID-19, the respiratory disease caused by the new coronavirus (SARS-CoV-2), continues to spread around the world and in the United States. Many countries are asking people to stay home and self-quarantine. In early March, the World Health Organization (WHO) officially called the disease a pandemic—a disease outbreak occurring over a wide geographic area and affecting an exceptionally high proportion of the population. The U.S.U.S., which declared a national emergency in mid-March, now is reported to have the most detected cases in the world.

According to the WHO, globally, there have been almost 825,000 confirmed cases of people with COVID-19 and more than 40,000 people have died from the disease. This death toll has far surpassed that of the severe acute respiratory syndrome (SARS) epidemic that occurred in 2002 and 2003. (While some news sources report different numbers, the WHO provides official counts of confirmed cases once a day.)

In the U.S., numbers are changing daily, as different parts of the country experience different levels of COVID-19 activity. All 50 states have reported cases, with large clusters in certain areas, including New York City (the C.D.C. is providing a daily update of the numbers in the U.S., but says data provided by state public health departments should be considered the most up to date). The C.D.C. expects most people in the U.S. will be exposed to the virus in the coming months (such widespread transmission could mean large numbers of people needing medical care at the same time—which is why an important strategy is to try to delay the spread). 

Meanwhile, people in the U.S are facing significant disruptions, including unprecedented cancellations, postponements, and shutdowns of everything from schools to religious services as reports of community transmission grow. States and cities across the U.S. are asking or ordering people to stay home. President Trump has activated the National Guard to assist California, New York, and Washington, which have been hit especially hard. 

The agency has repeatedly said that ordinary citizens do not need to wear masks unless they are feeling sick. But with the new data on people who may be infected without ever feeling sick, or who are transmitting the virus for a couple of days before contacting ill, Mr Redfield said that such guidance was "being critically re-reviewed."

The new coronavirus continues to spread around the world, prompting governments to step up efforts to contain the spread of the disease it causes, officially known as COVID-19.

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More than 5,700 people have died globally from the disease, while more than 152,00 infections have been confirmed in dozens of countries, according to the World Health Organization, which has now declared the outbreak a pandemic

distance to stay away from Corona Virus

How is the coronavirus spreading?

The coronavirus - known as COVID-19 - spreads from person to person nearby, similar to other respiratory illnesses, such as the flu.

Droplets of bodily fluids - such as saliva or mucus - from an infected person are dispersed in the air or on surfaces by coughing or sneezing. These droplets can come into direct contact with other people or can infect those who pick them up by touching infected surfaces and then their face. According to scientists, coughs and sneezes can travel several feet and stay suspended in the air for up to 10 minutes. It is not yet known how long the virus can survive outside a host but, in other viruses, it ranges from a few hours to months. Transmission is of particular concern on transport, where droplets containing the coronavirus could pass between passengers or via surfaces like aeroplane seats and armrests. The incubation period of the coronavirus, the length of time before symptoms appear, is between one and 14 days.

Although not yet confirmed, Chinese health authorities believe the virus can be transmitted before symptoms appear. This would have significant implications for containment measures, according to Gerard Krause, head of the Department for Epidemiology at the Helmholtz Centre for Infection."It's unusual for respiratory diseases transmissible even before the first symptoms have occurred," he told Al Jazeera."But the consequences is that if it happens then, they have no public health means to sort out or to identify people at risk of transmitting because they don't even know that they're ill yet."Data has shown that it spreads from person to person among those in close contact (within about 6 feet, or 2 meters). The virus spreads by respiratory droplets released when someone infected with the virus coughs or sneezes.

While animals are believed to be the original Source, the virus spread is now from person to person (human-to-human transmission). There is not enough epidemiological information at this time to determine how easily this virus spreads between people. Still, it is currently estimated that, on average, one infected person will infect between two and three other people. 

The virus seems to be transmitted mainly via small respiratory droplets through sneezing, coughing, or when people interact with each other for some time nearby (usually less than one metre). These droplets can then be inhaled, or they can land on surfaces that others may come into contact with, who can then get infected when they touch their nose, mouth or eyes. The virus can survive on different surfaces from several hours (copper, cardboard) up to a few days (plastic and stainless steel). However, the amount of viable virus declines over time and may not always be present in sufficient numbers to cause infection.

The incubation period for COVID-19 (i.e. the time between exposure to the virus and onset of symptoms) is currently estimated to bet between one and 14 days. 

We know that the virus can be transmitted when people who have infected show symptoms such as coughing. There is also some evidence suggesting that transmission can occur from a person that is infected even two days before showing symptoms; however, uncertainties remain about the effect of transmission by non-symptomatic persons. 

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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, sneezes or talks.

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

Some recent studies have suggested that COVID-19 may be spread by people who are not showing symptoms. Maintaining good social distance (about 6 feet) is very important in preventing the spread of COVID-19.

Person-to-person contact is thought to be the main method of transmission for the SARS-CoV-2 virus, according to the Centers for Disease Control and Prevention (C.D.C.)Trusted Source.

Imagine sitting next to someone with a SARS-CoV-2 infection on the bus or in a meeting room. Suddenly, this person sneezes or coughs.

If they don't cover their mouth and nose, they could potentially spray you with respiratory droplets from their nose or mouth. The droplets that land on you will likely contain the virus.

Or perhaps you meet someone who contracted the virus, and they touched their mouth or nose with their hand. When that person shakes your hand, they transfer some of the viruses to your hand.

If you then touch your mouth or nose without washing your hands first, you may accidentally give that virus an entry point into your own body.

One recent small study trusted Source suggested that the virus may also be present in feces and could contaminate places like toilet bowls and bathroom sinks. But the researchers noted the possibility of this being a mode of transmission needs more research.

Pregnancy and breastfeeding

Medical experts haven't determined whether a woman can transmit SARS-CoV-2 in utero, through childbirth, or through her breast milk.

The C.D.C. currently recommends trusted Source that mothers with a confirmed case of the virus, as well as those who may have it, are temporarily separated from their newborns. This separation helps decrease the risk of transmission.

Women should speak with their healthcare providers about the benefits and risks of breastfeeding. The C.D.C hasn't released any official guidelines regarding whether women with confirmed or suspected cases should avoid breastfeeding. They have, however, suggested that these women take the following precautionary measures trusted Source:

  • Wear a face mask while breastfeeding, if possible.
  • Properly wash their hands before holding or breastfeeding their infant.
  • Properly wash their hands before touching a bottle or breast pump.
  • Clean the breast pump each time it's used.
  • They should also consider having someone who isn't sick use expressed breast milk in feeding the infant.

How Corona Virus Spreads

Spread from contact with contaminated 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. This is not thought to be the main way the virus spreads, but we are still learning more about this virus. C.D.C. recommends people practice frequent "hand hygiene," which is either washing hands with soap or water or using an alcohol-based hand rub. C.D.C also recommends routine cleaning of frequently touched surfaces.

Think of all the frequently touched surfaces where germs can lurk: kitchen counters, bathroom counters, doorknobs, elevator buttons, the handle on the refrigerator, handrails on staircases. The list goes on and on.

Experts don't know for sure how long the novel coronavirus can survive on these surfaces. But if the virus behaves like other, similar viruses, the survival time could range from several hours to several daysTrusted Source.

The type of surface, the temperature of the room, and the humidity in the environment may play a role in how long the virus can survive on a surface.

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But since we don't know for sure, if you think a surface may be contaminated, clean it thoroughly with a disinfectant. A diluted bleach solution or an EPA-approved disinfectant is likely the most effective trusted Source cleaner for this purpose.

And if someone in your home is sick, frequently clean those surfaces. Remember to wash your hands afterwards thoroughly. This is one of the major questions researchers are still working hard to answer. The first infections were potentially the result of animal-to-human transmission, but confirmation that human-to-human transmission was obtained in late January. As the virus has spread, local transmission has been seen across the world. Some of the most at-risk people are those that work in healthcare.

"The major concern is hospital outbreaks, which were seen with SARS and MERS coronaviruses," said Raina MacIntyre, a professor of global biosecurity at the University of New South Wales, Australia. "Meticulous triage and infection control is needed to prevent these outbreaks and protect health workers."

WHO says the virus can move from person to person via:

  • Respiratory droplets -- when a person sneezes or coughs.
  • Direct contact with infected individuals.
  • Contact with contaminated surfaces and objects.

A handful of viruses, including MERS, can survive for periods in the air after being sneezed or coughed from an infected individual. Although recent reports suggest the novel coronavirus may be transmitted in this way, the Chinese Center for Diseases Control and Prevention has reiterated, there is no evidence for this. Writing in The Conversation on Feb. 14, virologists Ian Mackay and Katherine Arden explain "no infectious virus has been recovered from captured air samples."

Further research has shown SARS-CoV-2 may linger in the air for extended periods, which is particularly notable for health workers. It's estimated the virus can stay suspended in the air for a period of about 30 minutes. Social distancing measures become even more important here because only those close to infected individuals are expected to be exposed to large quantities of the virus in the air.  

Precautions remain extremely important

Since threats like COVID-19 can lead to the circulation of misinformation, it's important to trust information only from reputable health organizations and government sources such as the C.D.C.C.D.C. and the WHO. "The public health infrastructure in the U.S.U.S. is a critical resource for leading the federal, state, and local response," Dr. Martinello says. Because knowledge about the new virus is evolving rapidly, you can expect recommendations to change frequently.

State and local authorities are making a variety of recommendations to slow the spread of the virus in the community. Guidelines from the White House called "15 Days to Slow the Spread" stress avoiding social gatherings of more than ten people; using the drive-thru, pick-up, or delivery options instead of eating in restaurants; avoiding discretionary travel or shopping; and staying away from nursing homes and long-term care facilities (since the elderly are at especially high risk for serious complications if they get the virus).

Many experts are also recommending that everyone practice voluntary "social distancing." 

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