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Editor’s note: The Economist is making some of its most important coverage of the covid-19 pandemic freely available to readers of The Economist Today, our daily newsletter. To receive it, register here. For more coverage, see our coronavirus hub

ONE OF THE most worrying symptoms of covid-19 is the way the coronavirus attacks the lungs of those infected. This means some patients need a ventilator to help them breathe until their lungs recover. But there is a dire shortage of these machines in hospitals, so intensive-care units will be overwhelmed. Urged on by worried governments, ventilator manufacturers are working flat out and forming partnerships with carmakers, aerospace firms and others to boost output as fast as possible.

But their efforts will still be not enough to meet soaring demand. So hope is riding on scores of new projects to develop breathing devices that could be made rapidly by non-specialist companies and small workshops. These are mostly simpler devices; some could even be assembled by DIY enthusiasts. The response to this call to arms is unprecedented.

Yet difficulties and dangers lie ahead. At present ventilation is about the only way doctors have to treat...

Editor’s note: The Economist is making some of its most important coverage of the covid-19 pandemic freely available to readers of The Economist Today, our daily newsletter. To receive it, register here. For more coverage, see our coronavirus hub

“WE ARE TRYING to fly the plane while we are building it.” That is how Richard Hunt from America’s department of health described caring for patients seriously ill with covid-19 in a training session on the subject on March 24th. The session was webcast to almost 2,000 people in 39 countries (most were in America). The questions sent in advance filled 25 pages, said Mr Hunt.

The thirst for clinical guidance is desperate. Three months after doctors in the Chinese city of Wuhan encountered the world’s first covid-19 patients, medics in more than 150 countries are treating growing numbers. British scientists reckon that 4.4% of those infected will need hospitalisation; about one in three of those requires treatment in an intensive-care unit (ICU). Doctors in ICUs treat severe pneumonia, the hallmark of a serious case of covid-19, all the time. But with this new disease they do not yet know which changes in a patient’s symptoms, blood tests or vital signs...