Slowing the rate of new cases requires dramatic measures and is the key to preventing healthcare systems from becoming overwhelmed.

The charts below use a logarithmic scale to make rates of change between countries with widely different caseloads easier to compare.

The charts below use a logarithmic scale to make rates of change between countries with widely different caseloads easier to compare.

The available data for confirmed cases does not represent the true number of cases because access to testing varies by country - and many people simply don’t have access.

The novel COVID-19 coronavirus has spread like wildfire around the world. In the early days of the outbreak, the doubling rate — the time it took for the number of cases to double — was between three and six days for many countries. Countries unable to slow that exponential growth have seen their healthcare systems overwhelmed as nurses and doctors became infected and critical supplies such as ventilators and protective equipment ran low.

The goal in every emerging outbreak is to slow the rate of infection. Aggressive measures can help flatten the curve, and countries that have shut down cities and limited travel have managed to slow the doubling rate.

Testing in the United States has been slow to ramp up. An initial batch of tests issued by the Centers for Disease Control and Prevention (CDC) were found to be faulty, and many state and local authorities have said they have not been able to test as many people as they would like. Still, by the first week of April, the United States had more cases than any other country in the world. Outbreaks in New York, New Jersey, Michigan and Louisiana overwhelmed hospitals, and sent state and local officials scrambling to acquire ventilators and personal protective equipment for hospital workers. Official stay-at-home orders have been left up to state and local governments.

Spain announced a nationwide, 15-day state of emergency on March 14, which restricted transportation and ordered bars, restaurants and most shops to close. But by the end of March, the Iberian country had the second-highest number of fatalities behind only Italy.

Italy had more than 105,000 confirmed cases and 12,000 deaths by the end of March. The country went on lockdown on March 10 when the government ordered everyone across the country not to move around, other than for work and emergencies, banned all public gatherings and suspended sporting events. After weeks of restrictions, the rate of new confirmed infections and deaths began to plateau.

Germany introduced border controls with Austria, Switzerland, France, Luxembourg and Denmark beginning March 16. They also closed schools, shops, restaurants, playgrounds and sports facilities, and many companies halted production to help slow the spread of the disease. The doubling rate of new infections had slowed to roughly five days by the first week of April after doubling every two days at the beginning of the pandemic.

France decided on March 17 to confine its residents to their homes to curb the spread of the virus as a daily surge of infections threatened the health system. By the end of March, France had over 52,000 confirmed cases and over 3,500 deaths.

Mainland China (excludes Hong Kong and Macau) recorded more than 81,000 cases by the end of March. In late January, with hospitals overwhelmed, the country put the entire province of Hubei — contaiting Wuhan, the city where the outbreak originated — on lockdown by restricting the movements of some 60 million people. Similar restrictions across China in the following weeks slowed the growth of new cases. The country’s National Health Commission said on March 12 that China has passed the peak of the epidemic.

Iran’s clerical rulers have struggled to contain the spread of the virus despite the closure of schools and universities and the suspension of religious, cultural and sports events across the country. The outbreak has infected a host of senior officials, politicians, clerics and members of the elite Revolutionary Guards.

United Kingdom Prime Minister Boris Johnson faced criticism for initially promoting a modest response to the outbreak, saying on March 3 that he had been shaking hands with coronavirus patients. He changed tack when scientific projections showed a quarter of a million people could die in Britain. Johnson effectively shuttered the world’s fifth-largest economy, advising people to stay at home and the elderly or infirm to isolate themselves for weeks. He tested positive for the virus on March 26 and was hospitalized on April 5.The prime minister was moved into intensive care on the following day.