Millions of people in developing countries die every year of conditions that are easily treatable elsewhere. They die not only because of lack of medicines but also because many are so undernourished that relatively mild complaints become killers.

The most lethal conditions are lower respiratory infections, AIDS and diarrhoeal diseases.

Also deadly are perinatal conditions that affect children in the period from just before to soon after birth. These conditions, which include low birth weight, birth asphyxia and birth trauma, kill 2.5 million babies a year.

The most vulnerable are children under five years old. More than 9 million die each year of diseases and perinatal conditions, nearly half because of malnutrition.

But disease not only kills. It can also debilitate people for life and make it harder for them to work. This perpetuates a vicious cycle that pushes them and their families further down the poverty ladder, making them even more susceptible to illness.

One caveat to bear in mind when researching health issues is that data is patchy for Africa, Middle East and Asia. The World Health Organisation relies on member states for health statistics, but not all countries conduct surveys and millions of births and deaths go unreported. That makes it difficult to build up an accurate picture of how diseases affect countries.

Our In detail section has sections on all the biggest killer diseases and conditions.

Disease/condition	Global annual death rates
Lower respiratory infections	3.9 million
AIDS (WHO 2002, UNAIDS 2005)	2.8 million
Perinatal conditions	2.5 million
Diarroeal disease	1.8 million
Tuberculosis (WHO 2002, 2005)	1.6 million
Traffic accidents (included for comparison)	1.2 million
Malaria (WHO 2006)	880,000
Measles	600,000
Maternal conditions	500,000
War (included for comparison)	200,000
(Source: Except where stated, World Health Organisation figures for 2002)