The COVID-19 pandemic has highlighted the severity and potential lethality of this virus. As of the writing of this article, confirmed global cases have surpassed 2.7 million, with a troubling number resulting in serious complications or fatalities. The death toll has approached 200,000, with a significant proportion occurring in the United States.

Despite the grim statistics, there is a glimmer of hope as social distancing measures appear to be effective, leading to a decrease in infection rates and daily fatalities. However, it is crucial to maintain low levels of social interaction during this pivotal time. While many advocate for the reopening of society, experts in network epidemiology caution against any physical contact with individuals outside one's household. Here’s the scientific rationale behind this caution.

In theory, if every household could effectively isolate, the disease would not spread between them, leading to a rapid decline in new infections. However, this scenario is unrealistic. People live in households and cannot completely isolate from one another. Additionally, they require essential services like food and healthcare, making total isolation impractical. If isolation were achievable, it could effectively halt the transmission of SARS-CoV-2, the virus responsible for COVID-19.

Conversely, if there are no efforts to minimize physical contact, the consequences would be dire. If individuals frequently interacted with each other, especially in a population with a notable percentage of infections, the virus would spread rapidly.

This situation would lead to an overwhelming public health crisis where infections peak simultaneously, which is precisely what the "flatten the curve" initiative seeks to prevent. Thanks to effective social distancing measures, this worst-case scenario has largely been averted so far.

The outcome of our actions now is crucial. If we persist in maintaining physical distance, we can expect a gradual decline in new cases and deaths. However, if distancing measures are lifted, some will choose to continue with them, while others will not. Among those who resume close contact, infection rates could quickly rebound, similar to the early stages of the pandemic. The principles of network epidemiology help predict the outcomes of different behavioral scenarios.

A recent study by network epidemiologists from the University of Washington investigated the implications of visiting just one person outside one's household without adhering to social distancing. They started from a realistic scenario in which only essential interactions occur. These interactions are unavoidable; healthcare workers need to engage with patients, and food service employees must interact with customers.

Even when all precautions are taken, there remains a significant risk of virus transmission, as evidenced by the many healthcare workers who have contracted COVID-19.

In this best-case scenario, where only essential interactions happen, the virus still has pathways for transmission. Medical professionals, food supply chain workers, and utility services all necessitate contact.

The connections that arise are not limited to direct interactions; networks of potential transmission can emerge, with the largest networks affecting a significant number of households. Researchers have indicated that some infections and fatalities are inevitable.

Let us be very clear here: some people are going to get infected, and some people are going to die, because of these connections. It’s that simple.

But these connections are so essential that we as a society are willing to make that trade-off. Without them, many more people would die of other basic things besides COVID-19: starvation, freezing, crime, other diseases.

If each individual is permitted to visit just one person from another household, the network's connectivity increases dramatically. Researchers often hear the question, “Is there really so much harm in meeting up with just one friend?”

While it may seem low-risk, especially when neither household contains vulnerable individuals, these connections can significantly enhance the interconnectedness of otherwise isolated households.

If every member of a household (averaging 2.6 people) visits just one individual outside their home, the ramifications become severe:

1. The largest connected cluster increases by 240% compared to the essential-only scenario.
2. Over 90% of households become interconnected, up from 26.5%.
3. The average household now connects to 36.8 other households within three degrees of separation, compared to just 4.2 in the essential-only scenario.

Even in a scenario where just one person from each household visits another, significant increases in connections are observed. The largest cluster grows by 168%, 71% of households connect, and the average household links to 12.1 others within three degrees.

In short, we see many more opportunities to acquire the virus from folks who are both near and far from you in the social network. And equally more opportunities for you to transmit it on to other folks both near and far.

All just so people can hang out with one friend!

The essential takeaway is that the collective health and safety of everyone, including ourselves and our families, depend on our actions moving forward. To save lives and slow the spread of this infection, we must postpone any non-essential connections with individuals outside our households.

While some connections are critical and must be maintained to prevent more significant health threats, every non-essential interaction poses a risk of disease transmission. This means that the consequences of visiting even one friend can be severe. Waiting until it is safe is worth the effort for everyone involved.