Medical experts are calling for the urgent introduction of a simple yet potentially highly effective way of protecting people from Covid-19.
Known as convalescent serum treatment, it involves extracting virus-killing antibodies from the blood of people who have recovered from the disease and donating them to those still at risk.
Used during the Spanish Flu pandemic of 1918/9, the treatment cut death-rates among the critically ill by half.
With an effective vaccine or anti-viral drugs still many months away, US government officials are being urged to revive the method, which could be up and running in a matter of weeks.
It is likely that governments around the world will come under similar pressure over the coming days.
"Covid-19 convalescent sera could be used to treat individuals with early symptoms and prevent disease in those exposed", said Professor Arturo Casadevall of Johns Hopkins Bloomberg School of Public Health, setting out the case for the treatment in the Journal of Clinical Investigation with colleague Dr Liise-anne Pirofski.
“Today, nurses, physicians, and first responders exposed to known cases of Covid-19, some of whom have developed disease, are being quarantined, which threatens to collapse the health care system”.
The treatment also has the potential to boost the survival chances of seriously ill patients.
It is understood that both the World Health Organisation and the US Food and Drug Administration are taking the proposal seriously.
This follows the successful use of convalescent serum treatment with small numbers of patients in several epidemics over the last 20 years, including the first SARS coronavirus outbreak of 2003, and the 2012 MERS epidemic.
Reports from China suggest it has also proved safe, and cut infection levels among patients in the ongoing epidemic of Covid-19.
Other experts agree that the treatment is worth trying. "It could be very effective", said virology professor Peter Hotez of Baylor College of Medicine in Houston, Texas.
“Having this at our disposal could be really important because otherwise we’ve got nothing – otherwise we got back to the 14th century in terms of using quarantine methods”.
Prof Hotez said that current estimates suggest that antibodies from a single recovered patient could be enough to protect dozens of health-care workers from infection.
A seriously ill patient may require the sera from one person who has recovered.
The use of donated blood sera involves several risks, including inadvertently infecting people with other blood-borne diseases and triggering immunological reactions.
Blood banks routinely screen for such effects, however, and the risks are thought to be acceptable.
Prof Casadevall and his colleagues have already begun drawing up guidelines for hospitals and blood-banks to allow them to put the treatment into operation.
But the biggest challenge is the need for nationwide co-ordination.
Speaking to NBC News, Prof Casadevall said the first priority must be mass testing programmes to find out who is infected.
Without this, it is impossible to identify those who successfully fight off Covid-19, allowing them to become potential donors.
He also called for the establishment of national networks of blood product shipments, to allow rapid movement of sera from regions in recovery to those where the epidemic is just taking hold.
Prof Casadevall envisages nationwide campaigns calling on those who tested positive and recover from Covid-19 report to serum collection centres to help those still infected.
However, all this requires rapid action by governments. “As we are in the midst of a worldwide pandemic, we recommend that institutions consider the emergency use of convalescent sera and begin preparations as soon as possible," said Prof Casadevall. "Time is of the essence”.
Robert Matthews is Visiting Professor of Science at Aston University, Birmingham, UK