Expert breaks down three risk levels for monkeypox transmission

By early August 2022, monkeypox had become impossible to ignore. California joined Illinois and New York in declaring a state of emergency as cases climbed past 5,800 across the country. The virus was spreading, but how—and how fast—remained a question many people were asking, especially as large public gatherings continued. San Francisco faced particular scrutiny: the Outside Lands music and arts festival was about to draw crowds to Golden Gate Park over three days, and public health officials were watching closely.

Dr. Peter Chin-Hong, an infectious disease specialist at the University of California San Francisco, offered a useful framework for understanding the actual risk. He divided monkeypox transmission into three categories: high, medium, and low. The distinction mattered because it separated genuine danger from theoretical possibility, and it helped explain why some activities posed real concern while others did not.

The highest-risk transmission occurred through prolonged skin-to-skin contact, particularly intimate contact. Chin-Hong explained the mechanics plainly: when two people are in close physical contact, small breaks in the skin are inevitable. If one person has an open sore from monkeypox, the virus can enter those tiny wounds with remarkable efficiency. This was the primary way the disease spread, and it was why the virus had found particular footing in certain communities and settings.

Medium-risk transmission happened through shared bedding and clothing. The virus could survive on fabric, especially if someone with an active lesion had slept in the bedding or worn the clothing. It was less direct than skin-to-skin contact but still plausible enough to warrant caution. Casual contact—a handshake, a brush in a crowd—fell into the low-risk category. Even then, transmission required a specific scenario: both people would need to have open wounds, and the virus would need to make contact with those wounds. It was possible in theory but unlikely in practice.

Chin-Hong emphasized an important temporal boundary: monkeypox could only spread from the moment someone felt sick until their rash had completely scabbed over. This window of contagiousness was finite and knowable, which meant people who recognized their symptoms could take steps to isolate.

When it came to Outside Lands specifically, Chin-Hong's concern was not the festival itself but what happened afterward. Thousands of people gathering in an open park, moving through crowds, listening to music—that posed minimal risk. The danger lay in the private encounters that followed: the parties in hotel rooms, the intimate gatherings after the music stopped, the closed-door events where people were in sustained close contact. "Risky activities are not in Outside Lands," he said. "It's in the events or the intimate settings that people have or encounters they have after the event."

Vaccination emerged as the most powerful tool for breaking the chain of transmission. The available vaccines could abort the disease entirely if administered within four days of infection—a narrow but meaningful window. Unlike the COVID-19 pandemic, which had demanded mass vaccination campaigns, monkeypox experts believed targeted vaccination could work. By vaccinating people at highest risk and those who had been exposed, public health officials could contain the outbreak without inoculating the entire population. The World Health Organization had designated monkeypox a global health emergency, and the Biden administration was mobilizing: Robert Fenton from the Federal Emergency Management Agency and Dr. Demetre Daskalakis from the Centers for Disease Control and Prevention were being named as White House coordinators to oversee strategy, increase access to tests and vaccines, and ensure equitable distribution of treatments. The outbreak was serious, but the response suggested it was manageable if resources were deployed strategically.