Global patterns of mortality
Some of the highest crude death rates are found in less developed countries, particularly in sub-Saharan Africa. Liberia, Niger, Sierra Leone, Zambia and Zimbabwe all have death rates of 20 or more per 1,000. However, some of the lowest mortality rates are also found in countries at the lower end of the development range, for example Kuiwait (2 per 1,000), Hahrain (3 per 1,000) and Mexico (5 per 1,000).
Infant mortality is falling across the world, but there are still wide variations between nations – 142 infant deaths per 1,000 births in Liberia, compared to 3 per 1,000 in Finland. Areas with high rates of infant mortality have high rates of mortality overall.
HIV/AIDS is having a major impact on mortality around the world but especially in Sub-Saharan Africa. More than 40 million people are now living with HIV/AIDS, over 25 million of them in sub-Saharan Africa. In Swaziland, Botswana, Lesotho and Zimbabwe, over 20% of the total population of the country are affected. Asia is also badly affected and of the 7 million HIV/AIDS victims in south/southeast Asia, over 5 million live in India. It is estimated, however, that infection rates have begun to decline in a number of countries.
Mortality rates in the under 5’s
Global patterns of morbidity
Patterns of morbidity vary according to the nature of the illness.
Infuenza is caused by a virus that attacks the upper respiratory tract – the nose, throat and bronchi and sometime the lungs. The infection usally lasts for about a week. It is characterised by sudden onset of high fever, headache and severe malaise, non-productive cough and osrt throat. Most people recover within 1-2 weeks withou requiring any medical treatment.
In the very young, the elderly and people suffering from chronic medical conditions sich as lung diseases, diabetes, cancer, kidney or heart problems, influenza poses a serious risk. in these high-risk people the infection may lead to severe complications, pneumonia and death.
Influenza spreads around the world in seasonal epidemics and imposes a consideralbe economic burden in the form of hospital and other healthcare costs and low productivity. In annual influenza epidemics 5-15% of the population are affected with upper respiratory tract infections. Hospitalisation and deaths mainly occur in high risk groups. Althogh difficult to assess, these annual epidemcis are though to result in between 3 and 5 million cases of severe illness and between 250,000 and 500,000 deaths every year around the world. Most deaths currently associated with influenza in industrialised countries occur among those over 65 years of age.
Much less is know about the impact of influenza in the developing world. However, influenza outbreaks in the tropics, where vital transmission normally continues year-round, tend to have high attack and case mortality rates. For example, during an influenza otubreak in Madagascar in 2002, more than 27,000 cases were reported in 3 months and 800 deaths occurred despite rapid intervention. An investigation of the outbreak, co-ordinated by the World Health Organisation (WHO), found that there were sevre health consequences in poorly nourished populations with limited access to adequate healthcare.
Three times in the last century, influenza viruses have undergone major genetic changes resulting in global pandemics and large tolls in temrs of both disease and deaths. The most infmaous pandemic was ‘Spanish flu’ which affected large parts of the world population and is though to have killed at least 40 million people in 1918-1919. Two other influenza pandemcis have occurred in 1957 (‘Asian influenza’) and 1968 (‘Hong Kong influenza’) and cuased significant morbidity and mortality globally. In contrast to current influenza epidemics, these pandemcis had severe outcomes among healthy younger persons, although not on such a dramatic scale as the ‘Spanish flu’ where the death rate was highest among healthy young adults. Limited outbraks of a new influenza subtype (H5N1) directly transmitted from birds to humans occurred in Hong Kong Special Administrative Region of China in 1997 & 2003 and there have been fears that this could caused a pandemic.
Yellow fever is a viral disease that has couased epidemcis in Africa and thr Americas. It can be recognised in historic texts stretching back 400 years. infection causes a wide spectrum of disease, from mild symptoms to severe illness and death. Ths ‘yellow’ in the name is explained by the jaundice that affects some patients. Although an effective vaccine has been available for 60 years, the number of people infected over the last two decades has increased and yellow fever is now a serious public health issue again.
The vrus reamins silent in the body during an incubation period of 3-6 days. There are then two phases. Some infections have no symptoms whatsoever, but the first ‘acute’, phase is normally characterised by fever, muscle pain (with prominent backache), headache, shivers, loss of appetite, and nausea or vomiting. Often, the high fever is associated with a slow pulse. After 3-4 days, most patients improve and thier symptoms disappear.
However, 15% eneter a ‘toxic phase’ within 24 hours. Fever reappears and severa; bodily systems are affected. The patients rapidly develops jaundice and complains of abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes and stomach. Once this happens, blood appears in the vomit and faeces. Kidney function deteriorates; this can range from abnormal protein levels in the urine to complete kidney failuer with no urine production. Half of all patients in the ‘toxic phase’ die within 10-14 days.
The virus is constantly presnt at low levels of infection (i.e. endemic) in some tropical areas of Africa and the Americas. This viral presence can amplify into regular epidemics. Yellow fever outbreaks have also occurred in Europe, the Carobbean Islands, and Central and North America. 33 countries, with a combined population of 508 million are at risk in Africa. These lie within a band from 15N to 10S of the Equator. In the Americas, yellow fever is endemic in 9 South American countries and in several Caribbean islands. Bolivia, Brazil, Colombia, Ecuador and Peru are considered at greatest risk. There are estimated to be 200,000 cases of yellow fever (with 30,000 deaths) per year. Howver, due to under-reporting, only a small % of these cases are identified. Small numbers of imported cases also occur in countres free of yellow fever. Although yellow fever has never been reported in Asia, this region is at risk because the appropriate primates and mosquitoes thought to transmit the disease are present.