As the World Health Organization reports that poor countries need an extra 4m health workers, the BBC's Said Penda reports from Zambia, one of the worst affected countries.
Despite the lack of doctors and nurses, clinics in rural areas have started offering free health care starting this week, thanks to savings that have come through debt relief but the clinics have been overwhelmed by the demand.
Miria Mware is waiting on a bench outside the consulting room at Kafue hospital, her eyes red with tears.
Nurses are dealing with ever-increasing numbers of patients
"I've been here more than eight hours and I still haven't managed to see a doctor."
In rural areas like Kafue, 45 km south of the capital, Lusaka, "doctor" can mean simply a nurse.
Miria Mware's situation is not the result of free health care, but it does illustrate the problems that can result when millions of poor people, who in the past were unable to go to hospital, arrive at rural clinics.
In Kafue district, there are only seven doctors for a population of more than 250,000, says Dr Mwila Kaunda Lembalemba, who is in charge of health services in the district.
"It's true that it's a difficult challenge, particularly because of the shortage of health personnel," he says.
Dr Lembalemba is optimistic that the health services will be able to deal with the greater case load
"We operate with 50 to 60% of the staff we need, but we're doing everything to relieve the shortfall," he says.
Most Zambians, particularly those in the countryside, are still unaware that they can now seek free health care.
Only 300m from Kafue hospital, a teenage mother who was harvesting maize knew nothing about free treatment.
But others do know. "Turnout has been exceptional since Monday - it's people who weren't coming before because they had no means of paying: often it's the poorest of the poor," Dr Safare of Kafue hospital told the BBC.
"We risk becoming overwhelmed as soon as everyone in the countryside learns that it's already free," Dr Safare says.
A Heath Ministry official, who did not want to be named, expressed similar fears: "Under the pressure of the flood of patients who are going to take the opportunity of free health care, health personnel risk giving patients less time and less attention, putting quantity ahead of quality."
But Dr Lembalemba does not share these worries, believing the Zambian government is working in good faith and that "the measures that have been taken are a cause for optimism".
The government is trying to encourage new nursing recruits
He points to measures taken by the government in the last few years, either to keep health workers in the profession, or to recruit new staff.
Yet the figures do not encourage optimism. The country has one doctor for every 14,000 people, as compared with one in 600 in the United Kingdom, for example.
In a country that is home to 11m people, there are only 600 doctors, 24 pharmacists and not a single psychiatrist.
In July last year, Zambia secured $4bn in debt relief during the G8 summit at Gleneagles in the United Kingdom.
According to a World Health Organization official who is in the country to mark World Health Day on 7 April:
"If a good part of the money that Zambia was having to pay in debt repayments is effectively invested in health, the country can meet the enormous challenge that it faces in delivering free care."