Self-reported smell and taste changes are early indicators of the COVID- 1 19 pandemic and of the effectiveness of political decisions 2 3 4

In response to the COVID-19, many governments have taken unprecedented measures in peacetime, to avoid an overflow of intensive care units and critical care resuscitation units (CCRUs). Due to the heavy societal and economic impact of measure such as the lockdown1, accurate means to characterize the spread of the disease would be extremely helpful for the reopening strategies. Concurrently, smell and taste changes have been identified as among the most specific symptoms of COVID-192,3. Here, we show that self-reports of smell/taste changes are more closely associated with hospital overload and are much earlier than the current governmental indicators. We also show a decrease of new onset as early as 5 days after the lockdown enforcement, which is consistent with a rapid effect of the lockdown on the pandemic. Cross-country comparisons show countries with the most stringent lockdown measures (France and Italy) present a faster decline in new reports of the onset of smell/taste changes after the lockdown than a country with less stringent measures (United Kingdom). Public health decision makers could thus monitor self-reported changes in the ability to smell or taste i/as an early and specific indicator of the COVID-19 pandemic, and ii/to evaluate the success of reopening strategies.