Communicable diseases / by Giorgio Torrigiani and William Parra

Communicable diseases by Giorgio Torrigiani and William Parra Or Giorgio Torrigiani is Director of WHO's Division of Communicable Diseases and Mr William Parra is Management Support Officer for the same division Communicable diseases , in WHO's parlance, are those which are transmitted either from human to human, from ani- mals to people , carried to us by in- sects or other "vectors," or con- veyed to us in the air we breath , the water we drink and the very ground we tread on. A large number of them are so firmly entrenched in human com- munities that we tend to take them for granted- infections like the common cold, or influenza , or chickenpox. It is easy to forget that, for at least two millennia to our knowledge, smallpox too was " tak- en for granted" by generation upon generation ; yet just 13 years of global effort sufficed to wipe it from our planet. Many of these communicable dis- eases, in fact , are fostered by low standards of environmental sanita- tion , malnutrition, inadequate so- cial and economic development, and general ignorance of simple changes in behaviour that could help to avoid infection. And some diseases contribute to levels of sick- ness , disability and death-parti- cularly in children aged under five in the developing world- that are simply unacceptable in the closing decades of the 20th century. · Acute diarrhoea! diseases alone (including cholera) represent the primary cause of child mortality in developing countries and contri- bute to one-third of the 15 million deaths in this age group each year. Another one-third result from acute respiratory infections , pri- marily pneumonias. In addition, these infections are the leading cause of sickness in virtually all countries. Parasitic diseases , in particular malaria , filariasis, schistosomiasis and trypanosomiasis , remain as se- rious public health problems on a WORLD HEALTH, July 1988 global scale, and put the brake on attempts to develop many tropical areas. Efforts to control them may drain a sizeable proportion of the available resources in countries where these diseases are endemic. An estimated 17.5 million people are infected with onchocerciasis (river blindness) and about 340,000 are blind as a result; an additional Vaccination has proved to be one of the most cost-effective methods of protect- ing human health. Left: A household put at risk by inade- quate housing in the Western Pacific. Photos W HO/Zafar one million individuals are consid- ered to have suffered significant loss of sight , leaving them partially disabled. Tuberculosis and leprosy still constitute significant public health problems, while viral haemorrhagic fevers continue to have a major im- pact , particularly during epidemic outbreaks, in many countries . Sex- ually transmitted diseases are on the increase throughout the world , with a general shift towards youn- ger age groups. And even while the number of pathogens found to be sexually transmitted has been in- creasing in recent years, the disease spectrum in this area has been fur- ther complicated by the emergence of acquired immunodeficiency syn- drome (AIDS) and its various dis- ease manifestations . A matter of persistent concern is the increasing resistance of mi- crobes to drugs as well as resistance of insects and other vectors to chemical pesticides- trends that im- pede progress in disease reduction and increase the costs of control operations. Rapid expansion of the cities, the boom in travel and popu- lation movements , and increasing trade in human and animal foods within and between countries- all these have increased the risk of dis- eases being rapidly transmitted from one country or region to another. The burden of many communi- cable diseases could undoubtedly be reduced by environmental man- agement, by which we mean pro- viding safe water supply and the sanitary disposal of refuse , waste- water and excreta, ensuring ade- quate housing , safeguarding the en- vironment from chemical pollution and other control technologies. But building up these control measures is , of necessity, a slow process. In big cities, they require a large capi- tal investment, while in the vast ru- ral areas of the Third World , envi- ronmental management can only take place as part of the overall social and economic development. So emphasis will continue to fall on traditional methods of prevent- ing and controlling communicable diseases . These methods include setting up and maintaining surveil- lance systems to enumerate and 3 Communicable diseases evaluate all cases that occur, a ma- jor first step in determining the distribution , responsible factors, severity and extent of each com- municable disease. This in turn provides the necessary base-line information for setting the right priorities for applying disease con- trol strategies. Other control efforts include building up manpower resources through training programmes in technical and managerial areas, in- creasing the number of skilled per- sonnel engaged in communicable disease control activities, and de- veloping simple diagnostic tech- niques and inexpensive means of treatment that primary health care workers can deliver even in remote villages. And today there is re- newed interest in " health promo- tion" aimed at showing people how Tuberculosis remains a significant pub- lic health problem in many countries. This young Burmese mother is being treated for TB in her own home. Photo WHO 4 to avoid disease , to actively seek health and maintain healthy life- styles, all of which will directly con- tribute to the prevention or early treatment of many communicable diseases. Research is another important component of disease prevention and control activities, and thanks to modern biotechnology the hunt is on for new and inexpensive drugs , diagnostics and vaccines. It is par- ticularly important to develop new drugs to counter the many disease- causing organisms which are be- coming increasingly resistant to existing antibiotics. Vaccines, by contrast , have proved in recent history to be one of the most cost-effective methods of protecting human health . The in- tensive immunization programme mounted by WHO was the key to the global eradication of smallpox by 1977. Inspired by this success, WHO initiated , in 1974; the Expanded Programme on Immunization, a programme designed to immunize the children of the world against six common childhood diseases. AI- though no reliable figures on immu- nization coverage were available at that time, it could be estimated from the total quantities of vaccines being used , that fewer than five percent of children in their first year of life were receiving the vital third dose protecting them from polio , as well as diphtheria , whoop- ing cough and tetanus (DPT). As a result , some five million children died each year from vaccine-pre- ventable diseases; another five mil- lion more were crippled, blinded or mentally damaged. Today, immunization coverage in the developing countries (excluding China) had increased to 50 percent in 1987 for a third dose of DPT or polio vaccine. The stage is now set to add newly available vaccines to existing immunization schedules, and to further strengthen national managerial capabilities to ensure immunization and other kinds of health care for mothers and children. WHO continues to promote and support several programmes aimed at developing vaccines, whether to control more effectively those dis- eases for which vaccines do not ex- ist, or to improve the efficiency of existing vaccines. Theoretically at least, it should now be possible to design vaccines which provide long- term protection without any of the side effects observed in the past. Despite encouraging results, new vaccines for general use are not go- ing to be available overnight. So WHO is not slackening its ef- forts to prevent and control com- municable diseases by existing and conventional means. But a research and development effort of this mag- nitude , and the introduction of improved disease prevention and control strategies, cannot be under- taken without encouraging coun- tries to build up still further their national capabilities in such fields as epidemiology, biological re- search and health systems research. In turn the essential elements of these new strategies have to be in- corporated rapidly into the curri- cula of training institutions, and health staff will need continuing education and complementary train- ing facilities. It goes without saying that WHO will continue to do its ut- most to collaborate with Member States and strengthen their capacity and efficiency in all these fields. • WORLD HEALTH, July 1988