Four million health workers are needed to combat the "chronic shortage" around the world, a report from the World Health Organization has warned.
Fifty-seven countries have a serious shortage of health workers, affecting children's vaccinations, pregnancy care and access to treatment, it said.
Thirty-six of these countries are in sub-Saharan Africa.
The WHO's World Health Report 2006 said the shortage affected how diseases such as HIV/Aids could be tackled.
It says that at least 1.3 billion people worldwide lack access to the most basic healthcare, often because there is no health worker.
The burden is greatest in countries overwhelmed by poverty and disease where these health workers are needed most.
The report led to calls for Western countries to stop "poaching" healthcare staff from these countries.
Sub-Saharan Africa has 11% of the world's population and 24% of the global burden of disease but only 3% of the world's health workers.
A lack of personnel, combined with a lack of training and knowledge, is also a major obstacle for health systems as they attempt to respond effectively to chronic diseases and bird flu.
The WHO says life expectancies in the poorest countries are half of those in the richest nations.
It says each country needs to improve the way in which it plans for, educates and employs its doctors, nurses and support staff, the report says and sets out a 10-year plan to address the crisis.
Child health need
It calls for national leaders to urgently formulate and implement country strategies for the health workforce, backed by international donor assistance.
Infectious diseases and complications of pregnancy and delivery cause at least 10 million deaths each year.
The WHO says there is clear evidence that having a higher ratio of health workers to people boosts infant, child and maternal survival.
Dr Timothy Evans, WHO Assistant Director-General, said: "Not enough health workers are being trained or recruited where they are most needed.
"And increasing numbers are joining a brain drain of qualified professionals who are migrating to better-paid jobs in richer countries, whether those countries are near neighbours or wealthy industrialised nations.
"Such countries are likely to attract even more foreign staff because of their ageing populations, who will need more long-term, chronic care."
The WHO is calling for more direct investment in the training and support of health workers.
It says health budgets should increase by at least US$10 per person per year in the 57 countries with severe shortages, to educate and pay for the four million health workers needed.
National and international funding would be needed to achieve this goal.
The report says that meeting that target within 20 years is "ambitious but reasonable".
The UK government said it was against poaching.
Health Minister Rosie Winterton said: "We have one of the strongest ethical recruitment codes in the world.
"The UK is the only rich country to have a policy of not actively looking for healthcare workers in deprived countries to staff the NHS."