Memorial Day weekend is usually a time to come together and honor those who gave their lives defending the nation. But sometime this weekend, we also will pass the milestone of 100,000 American lives lost to Covid-19.I have been asked many times this week whether it will be OK to visit family and friends this weekend. From an infection-control standpoint, the answer is no. You shouldn’t be mixing households until the new infection numbers in your area are much lower.But you’re going to do it anyway. I don’t blame you. We are all looking for some normalcy after spending the last two or three months in varying degrees of isolation.The trade-off is the risk that the mixing of households can add fuel to the viral fire. Our legs may walk the virus into new homes — homes with fresh new lungs. Our actions and the choices we make over the next few days and weeks will determine what the summer looks like for all of us. So I’d like to give you a few ideas for how to make your likely socialization this weekend safer.Let’s start by learning how your small weekend party has the potential to spread infection in a community. For SARS-CoV-2, the novel coronavirus that causes Covid-19, the reproductive number — or R-naught — is estimated to be between 2 and 3. This means, for every one person that is infected, they infect up to three others (as shown in the picture below). Those three in turn infect up to another 3 people. But this is an average, and not what happens in reality.In reality, transmission and infection is messier. In the picture below, we see the index case (first case) infect three people. Mary, the person at the bottom of the three infected by the index case, infects one person. John, in the middle, is infected, but does not infect anyone else. But Isabelle, at the top, infects 8 others.In both of these illustrations, the reproductive rate is 3. But the second image is more likely what occurs in our community. Why does this happen? Some infected people just shed more virus than others, while others have more interactions with people and therefore provide more opportunities for the virus to find a new host. When super-shedding and mobility go together, you end up with a lot of people infected.Does that group of newly infected people look like anything we are considering this weekend? Well, that is what we are trying to avoid. If you are going to meet up with people this weekend for a drink, some games and possibly a barbecue, I don’t want to be reading about your party as a case study in a few months.What can we do to safely enjoy our friends’ company? The key is to have a plan and to put that plan in place, and then you can relax and enjoy the time with friends.Plan the Guest ListKeep it in the family. The safest plan is to celebrate the weekend with your household unit only.Vet your guests. If you do invite guests, make sure they have the same level of concern for the risks of infection as your household. When concerns between households don’t align, it can make the gathering much more anxiety-inducing for everyone.Keep it small. Limit the number of different households joining you. The size of the household is not as important as the number of households. Each household is a different quarantine unit. The more households you put together, the higher the risk for infection.Prepare the Party SpaceKeep it outside. Outdoor gatherings are much safer than indoor gatherings. You substantially increase the risk of infection when gathering in indoor spaces.Create separate dining spaces. Set out two tables for food: one for your family, one for your guest family. Use disposable utensils, plates, cutlery where possible (bonus if they are biodegradable).Plan for seating. Have guests bring their own chairs if you want to be super safe. But if you have outdoor furniture that stays outside and hasn’t been used by a member of your own household for a day before your gathering, then your outdoor furniture is likely to be safe for your guests.Create a hand-washing station. If you don’t have access to sanitizing wipes or hand sanitizer, make sure soap and water are available. You can keep spray bottles, a bucket of water, soap and paper towels near the outdoor faucet or hose.Ensure that garbage bins are available outside. You don’t want the host having to touch used cups, plates and utensils that have been in the mouths of others.Plan the MenuMake it potluck. With the exception of food that will be grilled, guests should bring their own food, drink, ice and coolers and put them at their own tables. Shared food is a recipe for infection, as the virus can be transferred from dishes and serving spoons. If you’re not convinced, watch this video using glow germs and black light to show how sharing food means sharing germs.Avoid finger foods. No chips, no dips. Every hand that goes into that bowl is an opportunity for viral transfer. If you absolutely must have finger food, ensure that it is set up on your family’s designated table.Serve from the grill. Feel comfortable serving a hot dog or a hamburger directly off the grill onto a person’s plate. This virus is killed by heat.Socialize SafelyKeep your distance. Maintaining appropriate physical distancing between households is still important. Brief close-range contact is less of a concern than sustained contact. Don’t jump on the kids for walking too close to grandma, but be mindful of longer conversations in close proximity.Wear masks for conversation. Consider wearing masks when you are having long conversations. Ensure you put masks on the loudest people! We know that shouting and singing expels more droplets than talking, but even quiet speech can send viral droplets into the air.Create physical barriers. Given that some alcohol and long conversations may be involved, it is useful to create barriers to movement between households so that you don’t drift closer to one another as the gathering goes on. This can be as simple as spacing chairs appropriately, with a well-placed table between them, or if the space allows, a nice fire pit in between.Plan for bathroom breaks. Create an obstacle-free path directly to the bathroom. Have paper towels available, and ask guests to use them to turn off faucets and to open and close doors so germs aren’t spread on high-touch areas.Have FunKeep children occupied. As much as we need to limit interactions between children, we will likely find this effort futile. Games that bring children in close contact for a long time should be avoided. But brief, close-contact interactions are less of a concern than prolonged contacts. Get children off video games and the couch inside, and get them outside playing games.Avoid contact sports. Try to avoid games that bring you into close contact or result in lots of yelling. Tossing games, such as Frisbee or football, can be played, but remember objects that are touched more frequently with your hands may provide a vehicle for the virus to find its way into a new household.Feel comfortable swimming. A properly maintained pool will inactivate this virus. But still ensure appropriate physical distancing is maintained between households.Clean UpEveryone should toss their own garbage. Be mindful of used eating and drinking utensils. Dispose of them and wash hands.Leave the chairs and tables. Don’t feel as if you have to scrub down your own outdoor furniture that is used by your guests while they are in your yard. Time and weather will take care of the virus.Erin Bromage, Ph.D., is a biology professor at the University of Massachusetts, Dartmouth. His blog post, The Risks, Know Them, Avoid Them, has been viewed by more than 17 million people.