Case Definitions for
Selected Infectious Diseases

(published by PAHO Special Program on Health Analysis)

	Case Definition: Meningococcal Diseases Meningococcal disease occurs sporadically and in epidemics of meningococcal meningitis; the majority of cases occur in children <5 years. Meningococcal meningitis is the only form of meningitis to cause epidemics. The case-fatality rate is between 5% and 15%. While sub-Saharan Africa is the most severely affected area, epidemic meningococcal disease can affect any country. be_v22n4-casedef.htm
	Case Definition: Viral Meningitis Meningococcal disease occurs sporadically and in epidemics of meningococcal meningitis; the majority of cases occur in children <5 years. Meningococcal meningitis is the only form of meningitis to cause epidemics. The case-fatality rate is between 5% and 15%. While sub-Saharan Africa is the most severely affected area, epidemic meningococcal disease can affect any country. Meningococcal bivalent A, C and quadrivalent A, C, Y, W135 vaccines are available; immunization of the entire population should be considered to halt epidemics due to A and C serogroup meningocci. be_v22n4-casedef.htm
	Case Definition: Salmonellosis Salmonellosis is one the main causes of foodborne disease. Detection and control of outbreaks is complicated by the fact that there are over 2,200 serotypes of Salmonella species, several of which have multiple phage types. Laboratory-based surveillance of salmonellosis with definitive typing and antibiograms allows for rapid identification of clusters. Investigations can then concentrate on individual cases infected with the “epidemic” strain and lead to better identification of risk factors and implicated food items. Utilization of molecular methods can lead to even more accurate identification of “epidemic” strains. be_v23n1-casedef.htm
	Case Definition: Acute Viral Hepatitis Estimates suggest that worldwide, there are 385 million carriers of hepatitis B virus and 170 million carriers of hepatitis C virus. More than 1 million deaths each year are attributable to hepatitis B. Transmission is mainly oral-faecal for hepatitis A and E, percutaneous for hepatitis B, C, and D and sexual for hepatitis B. The course of the disease may be fulminating (e.g., hepatitis E in pregnancy); chronic infection and severe sequelae occur for hepatitis B, C, and D. Prevention measures include transfusion safety, safe and appropriate use of injections, promotion of safe sexual practices, and (for hepatitis A and hepatitis B) immunization. Hepatitis B is targeted by WHO for reduced incidence/prevalence, by means of vaccination programs in children under 1 year of age. This case definition is that recommended by PAHO for surveillance of the disease. be_v23n2-acute_viral_hepatitis.htm
	Case Definition: Leprosy Leprosy continues to affect a large number of people. In 1997 there were an estimated 1.5 million cases in the world. Control of the disease has improved with the introduction of multidrug therapy (MDT). WHO has targeted the disease for elimination by the year 2000, using a focused flexible approach. This includes making multidrug therapy available to all communities and areas, appropriate and good quality diagnosis and treatment, with evaluation through epidemiological surveillance and programme monitoring. This case definition is that recommended by PAHO for surveillance of the disease. be_v23n2-leprosy.htm
	Case Definition: AIDS be_v22n2-SIDA.htm
	Case definition: Legionellosis Legionnaires’ disease is a disease with epidemic potential and high case-fatality. Surveillance is important in order to detect epidemics and to institute appropriate investigations and control measures. In addition, the surveillance of sporadic disease may provide clues as regards source of disease and prevention. be_v22n1-cases.htm
	Case definition: Syphilis Although cases of syphilis decreased dramatically after the introduction of penicillin treatment in 1946, syphilis reemerged in the end of the sixties and has remained at high incidence levels in developing countries. Developed countries are now also experiencing outbreaks and countries in economic transition are experiencing a marked and widespread recrudescence. Syphilis prevalence data in pregnant women provide information about both latent and symptomatic syphilis in this group, and minimize the problems associated with general reporting of sexually transmitted syndromes (STD), which are subject to variations in health care seeking behavior. From the Epidemiological Bulletin, Vol. 21 No. 4 (December 2000) be_v21n4-cases.htm
	Case Definition: Anthrax, Brucellosis and Rabies Anthrax is a widespread zoonosis transmitted from domestic animals (cattle, sheep, goats, buffaloes, pigs and other) to humans by direct contact or through animal products. Human anthrax is a serious problem in several countries and has potential for explosive outbreaks (especially the gastro-intestinal form); while pulmonary (inhalation) anthrax is mainly occupational, the threat of biological warfare attacks should not be forgotten. Anthrax has a serious impact on the trade of animal products. From the Epidemiological Bulletin, Volume 21, Number 3. be_v21n3-cases.htm
	Case Definitions: Dengue Fever and Leptospirosis Dengue Fever and Leptospirosis be_v21n2-cases.htm
	Case Definitions: Neonatal Tetanus and Tuberculosis Neonatal tetanus was targeted for elimination (9GPW) by WHO. Epidemiological surveillance is particularly useful in order to identify high-risk areas and monitor the impact of interventions. The overall objective of tuberculosis (TB) control is to reduce mortality, morbility and transmission of the disease until it no longer poses a threat to public health. Surveillance of tuberculosis helps obtain an accurate picture of the course of the epidemic in a community over time so as to allow timely intervention. Norms and Standards in Epidemiology. —from the Epidemiological Bulletin, Vol. 21 No.1, March 2000— eb_v21n1-tetantuberc.htm
	Norms and Standards in Epidemiology: Case Definitions: Cholera, Plague, Yellow Fever The use of case definitions is very important in epidemiology in order to standardize criteria for identification of cases. All case definition must include the three classical dimensions of epidemiological variables: time, place and person. It is of foremost importance to precisely define what will be considered as a case, in order to accurately monitor the trends of reported diseases, to detect their unusual ocurrences and, consequently, to evaluate the effectiveness of intervention. be991norms.htm
	Case definitions: Malaria and Poliomyelitis Diseases under epidemiological surveillance by WHO, established by the 22nd World Health Assembly, are louseborne typhus fever and relapsing fever, paralytic poliomyelitis, malaria and influenza. From this group of maladies, this issue of the Epidemiological Bulletin presents –in addition to its case definitions- a summary of some guidelines for epidemiological surveillance for paralytic poliomyelitis and malaria, taken from the WHO Recommended Surveillance Standards, 2nd. Ed., June 1999, revised by the PAHO’s Communicable Diseases Program. From the Epidemiological Bulletin, Vol. 20, No. 2 (June 1999) be992vigepi.htm
	Case definition: Measles and Rubella Measles surveillance is critical for measuring progress towards the goal of measles eradication in the Americas and for detecting problem areas. Rubella surveillance should be integrated with measles surveillance. The purpose of rubella surveillance is to detect circulation of rubella virus, not to detect every case of rubella. A separate rubella surveillance system is not needed. All sera from suspected rubella cases which test negative for rubella IgM antibodies should be tested for measles IgM antibodies and vice versa. From the Epidemiological Bulletin, Vol. 20, No. 3 (September 1999) be993measlesrub.htm
	Case Definition: Diphteria and Pertussis Diphtheria is a highly contagious bacterial disease that is transmitted from person to person through close physical and respiratory contact. It can cause large epidemics in areas of low vaccination coverage. Pertussis (whooping cough) is a highly contagious acute bacterial disease involving the respiratory tract. It is transmitted by direct contact with discharges from the respiratory mucous membranes of infected persons by the airborne route. Worldwide, an estimated 20-40 million cases and 200,000 deaths occur annually. From the Epidemiological Bulletin, Vol. 20, No. 4 (December 1999) be994diphtpert.htm