Even in the absence of detailed directives, however, there’s scientific consensus about a general approach that can reduce the spread of the virus as the world around you reopens.

The virus is spread most efficiently from person to person, but the Centers for Disease Control and Prevention nonetheless recommends frequent cleaning of high-touch objects and surfaces like tables, doorknobs, light switches, countertops, handles, phones, keyboards, toilets and faucets, touch screens, A.T.M.'s and gas pump handles.

Any 15-minute face-to-face conversation between people who are within six feet of each other constitutes close contact, said Dr.

The longer the conversation and the closer the physical proximity between the participants, the greater the risk of the virus spreading if one person is infected.

In one case investigated by federal health officials, an individual with mild respiratory symptoms attended a funeral in Chicago in February, setting off a chain of transmission that led to more than a dozen people getting sick and three deaths.

As various relatives fell ill, household members who took care of them were also infected; birthday party guests who had contracted the virus went to church, infecting congregants sitting in the next row.

Altogether, 15 people were infected.

A flow of fresh air dilutes the virus, she added: “When you’re next to a good air flow source or by a window, your upper respiratory tract won’t be exposed to that much virus anymore.”.

And of the 30 people who were infected, most had traveled on the bus to the temple and back with the first person who became ill, about an hour’s drive each way.

On that bus, no one sitting by an open window got sick, with the sole exception of an individual who sat directly next to the infected woman.

Mass protests against police brutality that have brought thousands of people onto the streets in cities across America are raising the specter of new coronavirus outbreaks, prompting political leaders, physicians and public health experts to warn that the crowds could cause a surge in cases.

While many political leaders affirmed the right of protesters to express themselves, they urged the demonstrators to wear face masks and maintain social distancing, both to protect themselves and to prevent further community spread of the virus.

Some infectious disease experts were reassured by the fact that the protests were held outdoors, saying the open air settings could mitigate the risk of transmission.

A number of studies of flu, rhinovirus, coronavirus and other microbes have shown that respiratory illnesses, including the new coronavirus, can spread by touching contaminated surfaces, particularly in places like day care centers, offices and hospitals.

But a long chain of events has to happen for the disease to spread that way.

The best way to protect yourself from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing your hands, not touching your face and wearing masks.

A study from Emory University found that during flu season, the safest place to sit on a plane is by a window, as people sitting in window seats had less contact with potentially sick people.

If you don’t have a thermometer (they can be pricey these days), there are other ways to figure out if you have a fever, or are at risk of Covid-19 complications.

This is a shift in federal guidance reflecting new concerns that the coronavirus is being spread by infected people who have no symptoms.

If you’ve been exposed to the coronavirus or think you have, and have a fever or symptoms like a cough or difficulty breathing, call a doctor.

“There’s more potential for one of those 500 people to have Covid-19 and be spreading it,” she said.

People at high risk for developing severe disease if they become infected with the coronavirus will want to take the greatest of precautions

That group includes those 65 and over; residents of nursing homes and long-term care facilities; and people with compromised immune systems, chronic lung or kidney disease or heart conditions or who are severely obese

But young, healthy adults and children should also consider the protection of people around them, including family members, colleagues or friends who are vulnerable because of chronic disease or other life circumstances, Dr

“Although I’m not in a risk group, I’m regularly in contact with people who are, so it comes down to not just thinking about ourselves, but our whole communities, and how we all have to protect one another.”