If the past two years have taught us anything, it’s that testing for viral diseases is complicated. Sometimes, the tests are difficult to get, like in the early days of COVID-19. And even if people have access to testing, they might not feel they need it. People with COVID-19 often don’t have symptoms and may not always know to get tested. And now, with the availability of at-home self-tests, most people test themselves and don’t report the results. With other diseases—such as monkeypox—stigma surrounding the disease and the group most affected can deter access to testing.

These limitations hinder health authorities’ ability to learn more about infectious diseases and control their spread. If you can’t detect a problem, you can’t direct resources to help fix it.