It is time to start solving the mystery of Long Covid, an aspect of the pandemic blighting millions of lives, the World Health Organization's leader on post-Covid conditions told AFP.
Little is known about why some people, after coming through the acute phase of Covid-19, struggle to recover and suffer ongoing symptoms including tiredness, brain fog, cardiac and neurological disorders.
At this stage of the pandemic, the world is fixated on vaccine roll-out and new, more contagious variants of the coronavirus.
However, Long Covid deserves similar urgent attention, said Janet Diaz, the clinical care lead in the WHO's emergencies programme, ahead of a push for a globally-unified approach to the problem.
"We still don't fully understand what Long Covid is," Diaz told AFP in an interview outside the WHO's headquarters in Geneva.
"There's quite a bit to learn, but I am confident that the scientific community is really rallying around."
Tellingly, Long Covid does not yet have a proper name.
The WHO currently calls it post-Covid condition, while other terms in circulation include post-acute Covid syndrome and Covid long haulers.
The WHO is hosting a first global seminar on Long Covid on February 9. It will bring scientists, experts and clinicians together to define the condition, give it a formal name and harmonise study methods.
"It's a condition that needs further description, further understanding of how many are affected and further understanding of what is causing it, so we can better prevent, manage and treat it," said Diaz, 48, a US respiratory physician and intensive care doctor.
She said British and other studies suggested potentially one in 10 cases may have prolonged symptoms one month after infection, but there was no picture yet of how long those conditions might persist.
The elderly and those with underlying conditions are most at risk of serious disease from Covid-19.
But the profile of Long Covid patients does not match. It affects people with varying degrees of severity of disease and "seems to potentially also include younger people", including children, said Diaz.
While the pandemic response priority remains preventing people from catching the virus and falling ill, treating coronavirus cases "must also now include care after the acute illness... until you get back to full health", Diaz said.
CRACKING THE CODE
Diaz said fatigue seemed to be the most common symptom, with others including post-exertional malaise, cognitive dysfunction or brain fog, shortness of breath, heart palpitations and neurological problems.
"How these are all related -- that's what we don't understand. Why would one person get this, and the other person get that?" asked Diaz, saying researchers needed to crack the underlying mechanisms of the disease that were causing these persistent symptoms.
"Is it something due to the virus? Due to the immune response? If we had a better idea, we could start to target some interventions to reduce symptoms."
Diaz said a "tremendous amount" of research was underway, largely classic observational studies following discharged patients.
She said the patient-led research had driven scientists to do further studies, and "collaboratively we should get to an answer quicker".
In a message to the potential millions still suffering long after they are officially considered recovered, Diaz said: "Stay hopeful".
"People may have prolonged symptoms, but we do know people are recovering. It may take a long time, but they are still recovering to previous health. We're with you."
Meanwhile, European Union efforts to secure Covid-19 vaccines received a much-needed boost after AstraZeneca promised to increase deliveries, while US Republicans were set to meet President Joe Biden to try and build bipartisan support for a huge national relief plan.
British-Swedish firm AstraZeneca will increase shipments of its vaccine to the EU by 30 percent, said European Commission chief Ursula von der Leyen Sunday, as the bloc struggles to get its mass inoculation programme up and running.
AstraZeneca had had previously said it could deliver only a quarter of the doses originally promised to Brussels for the first quarter of the year, sparking outrage and accusations it was giving preferential treatment to Britain.
In the US, ten Republican senators were set to meet Biden yesterday to present an alternative to his $1.3 trillion relief plan, arguing that a scaled-down approach could garner the bipartisan support he has said he seeks.
Senator Susan Collins, a moderate Republican from Maine, said that she had joined the group to present their own $600 billion package to help steer the world's worst-hit country out of historic health and economic crises.
The virus is known to have infected more than 102 million people so far -- with over 2.2 million deaths -- and countries are scrambling to vaccinate their populations and lift economy-crippling restrictions.
Kazakhstan began its campaign yesterday, with top health officials receiving Russia's Sputnik V vaccine in front of reporters.
Deputy health minister Erlan Kiyasov said he didn't "feel any sort of discomfort" after receiving a shot.
Also getting vaccinated in front of the cameras was the leader of the Maldives, as the tropical archipelago began its own rollout using doses donated from India.
South Africa yesterday took delivery of its first shipment of coronavirus vaccines, a move paving the way to the first phase of inoculation in Africa's worst-hit country.