The US had fewer than 70 cases of COVID-19, the respiratory disease caused by the novel coronavirus SAR-COV-2, on 1 March. Just two weeks later, the total case count has increased to over 5,000 cases. If we continue the exponential increase in the US since the beginning of March, we could be looking at over 228,000 confirmed cases by the end of the month.

The infections are growing at an exponential rate in a population that has never been previously exposed to the virus. GlobalData constructed three outbreak scenarios based on consensus low, moderate, and high growth rates. The consensus rates were calculated based on R0 studies, historical case trends, influencer accounts, and GlobalData’s internal analysis. Depending on how well the country carries out social-distancing measures, testing, and containment, we could be looking at a high end of almost two million cases by the end of March. A more conservative estimate places the US at around 228,000 cases, and a very optimistic estimate would be near 18,600 cases.

The three scenarios have such varied results because there are so many unknowns at this point. Characteristics of the outbreak that contribute to the large uncertainty include the virus’ long incubation period, a significant number of carriers with mild or no symptoms who are interacting with other at-risk people, inadequate testing, and inconsistent mitigation measures being implemented around the country. The Centers for Disease Control and Prevention (CDC ), for example, recommends cancelling events of more than 50 people, while The White House recommends cancelling events of more than ten people. School closures also vary by state, county, and sometimes even among school districts within the same county.

Under the high-risk scenario, we may expect that around 10% of COVID-19 cases require hospitalisation, equalling almost 200,000 cases that need hospital-level care at the same time, which is significantly more than US capacity. However, GlobalData does not expect the high-risk scenario to be very likely, especially if containment measures continue to escalate. As the US ramps up testing over the next few weeks, we may initially see a significant increase in cases. Improvement to testing is crucial to contain the epidemic as it allows identification of those who were infected and can thus be isolated in a timely manner.