The idea of building herd immunity – increasing the number of infected to such a degree that naturally occurring immunity would outstrip the coronavirus, while isolating the elderly and others at greatest risk of the disease – has been tossed around in the United States, the United Kingdom and elsewhere.  This week, however, from that approach.

But the kind of “herd immunity” strategy being discussed in the U.K. does not acknowledge a critical gap in our understanding of COVID-19, said , chair of the 91̽�� Department of Global Health and co-director of the MetaCenter for Pandemic Preparedness and Global Health Security to provide some perspective on the tactic.

The extensive interaction across age groups in most communities makes separation a challenge, she said.

“Grandparents are often the primary people taking care of children and adolescents while parents work (including working remotely), especially in lower-income families; and young adults are often the people who care for parents and other older adults who can no longer function completely independently,” Dr. Wasserheit said.

“Infection with this virus seems to be more likely to be mild, minimally symptomatic or asymptomatic in children, adolescents and young adults, and we know that transmission can occur in these settings. So it would be quite challenging to separate older adults from potentially infectious younger members of the population.

“In addition, we do not know how frequently immunity occurs after infection with this virus, and if it occurs, how strong that immunity is and how long it lasts.”

Washington Gov. Jay Inslee issued on Wednesday, March 11, an that limits large events to minimize risks to public health during the COVID-19 outbreak.

“Starting today, events that take place in King, Snohomish and Pierce counties with more than 250 people are prohibited by the state. This order applies to gatherings for social, spiritual and recreational activities. These include but are not limited to: community, civic, public, leisure, faith-based, or sporting events; parades; concerts; festivals; conventions; fundraisers and similar activities,” the proclamation states.

Here are how two 91̽��experts responded to questions about the order:

, a lecturer in the School of Public Health and co-director of the 

Why reduce crowd size?

“Social distancing is one of the strategies that we can take as a community to slow down the spread of COVID-19. Cancelling or postponing large gatherings is one way to promote social distancing.”

What is the ‘safest’ size?

“There is no ‘magic number’ for a ‘safe event.’ If a person with COVID-19 attends a public gathering, people who come into close contact with them may be at risk. Any time groups come together, individuals should keep at least six feet apart, wash their hands frequently, cough or sneeze into their sleeve, and replace their handshake with a smile, wave, nod, or other non-contact greeting. It’s harder to implement these social distancing measures at larger events.”

Dr. , chair of the 91̽�� Department of Global Health and co-director of :

Why reduce the number of people who can be at an event?

“The average number of new COVID-19 cases that each infected person generates is determined by three key things— how much contact the infected person has with uninfected, susceptible people, how long a person remains infectious and how easily the virus can spread. If we reduce the number of people at an event and we can do two things that will help reduce contact — decrease the total number of people exposed, and for those who do attend, increase the distance between them. That can decrease risk of exposure, particularly if they are more than 6 feet apart.”

Do crowd limits work? 

“By reducing crowding, we increase the space between people. For infections that are spread primarily by coughing and sneezing, helping people keep at least 6 feet between themselves and other people by limiting crowds can be a very important thing to do.”

What is the optimal number? Is it 250? 

“We do not know what the right number is, but this is definitely a case of ‘less is more.’ The smaller the group is and the less crowding there is, the more likely it is that people will stay safe and healthy.”

Dr. Wasserheit answers questions about the novel coronavirus pandemic in this video:

Quotes from Dr. Wasserheit in the video:

“The reason that we’re so concerned about this virus and this epidemic is — first of all — this virus is easily transmitted, it’s a respiratory virus. So if I’m infected and I sneeze or cough, it’s very easy for me to give it to somebody else. The second reason is that it’s a new virus. So we don’t have, as a population, immunity already to this virus. We haven’t seen it before.”

“The three most important things you can do to protect yourself, if you are currently healthy, are the things your mother would have told you. First of all, wash your hands regularly with soap for at least 20 seconds. Secondly, if you haven’t gotten your flu vaccine already, get it because this is the season for colds and flu, and the last thing you want to do is to be going in to the doctor or the ER where other people may be coming in who have this infection, and you’re exposed to them, but you could have prevented getting the flu. And the third thing is that if you do actually develop a cough or a respiratory infection, then stay home during that time. If you get really sick, see your doctor. And, for the people around you, cover your nose when you cough or sneeze!”

“There’s tremendous expertise across the 91̽�� in pandemic disease and global health security, from basic research all the way to public health interventions. And we have actually brought that together in a 91̽�� MetaCenter for Pandemic Disease Preparedness and Global Health Security.”

“This epidemic of the coronavirus will definitely not be the last time that this country and the world faces the outbreak of a pathogen with pandemic potential. We are seeing this more and more frequently, and these outbreaks have greater severity and magnitude. And so we definitely need to be better prepared in the future. That’s one of the most important lessons from the coronavirus outbreak.”