Enlarge / A US child infected with measles during a 2024 outbreak. The child’s cheek shows the characteristic rash associated with this viral infection. (credit: CDC)

With one of the highest vaccine exemption rates in the country, Oregon is experiencing its largest measles outbreak in decades. This year's count is now higher than anything seen since 2000, when the Centers for Disease Control and Prevention declared the highly contagious virus eliminated from the US.

Since the start of the year, Oregon has tallied 31 cases of measles, all in unvaccinated people. The cases have been accumulating in sustained waves of transmission since mid-June.

Last month, when the outbreak tally was still in the 20s, health officials noted that it was nearing a state record set in 2019. There were 28 cases that year, which were linked to a large outbreak across the border in Washington state. But, with that record now surpassed, the state is in pre-elimination territory.

Enlarge / People and their pets rest at the Oregon Convention Center cooling station in Portland as the city is hit with extreme temperatures caused by a heat dome on June 28, 2021 (credit: Kathryn Elsesser / AFP via Getty Images)

Northwest Oregon had never seen anything like it. Over the course of three days in June 2021, Multnomah County—the state’s most populous county, which rests in the swayback along Oregon’s northern border—recorded highs of 108°, 112°, and 116° Fahrenheit.

Temperatures were so hot that the metal on cable cars melted and the asphalt on roadways buckled. Nearly half the homes in the county lacked cooling systems because of Oregon’s typically gentle summers, where average highs top out at 81°. Sixty-nine people perished from heat stroke, most of them in their homes.

When scientific studies showed that the extreme temperatures were caused by heat domes, which experts say are influenced by climate change, county officials didn’t just chalk it up to a random weather occurrence. They started researching the large fossil fuel companies whose emissions are driving the climate crisis—including ExxonMobil, Shell, and Chevron—and sued them.