Surveillance and Control of Infectious Diseases
Sep 3rd, 2007 by admin
Introduction
Infectious diseases were the major cause of death worldwide as recently as the 1940s, before the development of antimicrobial drugs. In 1940, the death rate from tuberculosis was 45.9 per 100,000 population, compared to 0.5 per 100,000 in 1983. As a group, infectious diseases are currently estimated to cause 194,704 deaths yearly in the U.S. Only cardiovascular diseases (981,098 deaths in 1983) and cancer (442,986 deaths in 1983) cause more deaths. The evolution of new pathogens and the development of resistance in existing pathogens pose continuing challenges to medical scientists.
Whereas the morbidity and mortality data for cardiovascular disease, cancers and other diseases are collected as composite categories, the data for infectious diseases are normally not reported in the aggregate, but are reported for individual illnesses or organisms. To derive overall figures for the incidence and prevalence of infectious disease necessarily requires reliance on imperfect surveillance systems and on estimates by experts when reporting is incomplete. In this chapter, overall figures for the morbidity and mortality from infectious diseases as a group are based on the calculations of experts at the Center for Infectious Diseases of the Centers for Disease Control (CDC). For specific illnesses or organisms that are regularly reported to the CDC, the reported figures are used to facilitate comparisons. “Reported” cases invariably are less than the true incidence because of under-reporting, which for some diseases may be extreme. Sexually transmitted diseases and immunizable childhood illnesses are treated in separate chapters.
Prevalence
Morbidity and Mortality
A study estimates that 742,248,261 infectious disease episodes occur annually in the United States resulting in 194,704 deaths for a case-fatality rate of 26 per 100,000.
The same report estimates that each year infectious diseases result in 2,192,370 years of life lost before age 65, 42,029,624 hospital days spent, and nearly 2 billion days lost from work, school and other major activities.
The total direct cost of infectious diseases, not including the cost of deaths, lost wages, decreased productivity, reactions to treatment, or other indirect costs, is estimated at $17.2 billion annually.
The five major causes of morbidity from infections are, in decreasing order of magnitude, viral, upper respiratory, cutaneous, vaccine preventable and bacterial.
The 5 leading contributors to mortality from infections are, in decreasing order of magnitude: bacterial; lower respiratory, including pneumonia and influenza; nosocomial; vaccine preventable; and viral.
Lower Respiratory Infections
Lower respiratory infections including pneumonia and influenza have an estimated incidence of 22 million annual cases and result in 79,000 deaths each year in the U.S.
Lower respiratory infections result in an estimated 7.3 million hospital days per year and result in direct costs of $2 billion annually.
The current incidence of pneumococcal pneumonia is 9 cases per 100,000 population. As many as 400,000 cases of pneumococcal pneumonia occur each year in the U.S. In the elderly and those with underlying disease, the case fatality rate is 25%-35%.
Tuberculosis
In 1983, 23,846 cases of tuberculosis were reported to the CDC for a rate of 10.2 cases per 100,000 population. 1,779 deaths from tuberculosis were reported in 1983, for a rate of 0.8 deaths per 100,000.
In 1983, 1,360 tuberculosis cases were reported among children under 15 years of age including 818 cases among children under 5 years of age. The tuberculosis case rate increases with age for all races and sexes, with nonwhite males over 65 years of age having the highest rate at 130 cases per 100,000 population.
In 1985, a provisional total of 21,801 tuberculosis cases were reported to the Centers for Disease Control, a 2.0% decline from the 1984 final total of 22,255 cases.
A CDC survey on the resistance of tuberculosis isolates to anti-tuberculosis drugs over a 7.5-year period ending in 1982 revealed that 6.9% of isolates were resistant to one or more drugs tested. 92% of the resistant isolates were resistant to isoniazid and/or streptomycin.
Large racial and ethnic differences in rates of primary drug resistance in tuberculosis isolates exist, with Asians having the highest rate (14.8%) followed by Hispanics (11.8%), Blacks (6.1%), whites (4.9%) and American Indians (4.1%).
Upper Respiratory Infections
Upper respiratory infections cause little mortality but result in significant outpatient care visits and costs. It is estimated that 429 million upper respiratory infections occur annually in the U.S. resulting in $2.5 billion in direct costs.
Enteric Infections
Enteric infections from all causes result in 224 million annual cases and 38,000 annual deaths in the U.S., according to CDC estimates.
It is estimated that enteric infections are responsible for 9 million hospital days yearly and incur direct costs of $3 billion yearly.
44,250 cases of salmonellosis (excluding typhoid fever) were reported in 1983, but the estimated true incidence of symptomatic illness caused by salmonella is 2 million. 40% of the salmonellosis cases with age reported occurred to children under 5 years of age; however, the rate increases noted since 1977 have occurred primarily among older age groups.
In 1986, 26,550 cases of giardiasis were reported in the U.S. Most infections were attributed to drinking improperly treated municipal water or exposure to an infected, diaper-age child in a day care setting. Giardia is the most common enteric pathogen identified in children who attend day care centers.
In 1983, 19,719 cases of shigellosis were reported in the U.S. Whereas salmonella is most commonly isolated from children less than one year of age, shigella is most commonly isolated from two-year olds. The true annual incidence of symptomatic illness caused by shigella is about 300,000 infections.
Hepatitis
Provisional data for 1985 indicate there were 58,986 total cases of viral hepatitis in the U.S., including 22,959 cases of hepatitis A, 26,316 cases of hepatitis B, 4,002 cases of non-A, non-B hepatitis and 5,709 cases in which the type was unspecified. The true annual incidence is estimated to be 48,000 for hepatitis A, 128,000 for hepatitis B, and 50,000 for non-A, non-B hepatitis.
All types of hepatitis are more commonly seen among persons 20-29 years of age than any other age group. The Viral Hepatitis Surveillance Program reported that in 1984, 69% of hepatitis B cases, 50% of hepatitis A cases and 57% of non-A, non-B hepatitis cases occurred to those 2039 years of age.
In 1984, hospitalization as a result of hepatitis was reported for 30% of those with hepatitis A, 40% of those with hepatitis B, and 44% of those with non-A, non-B hepatitis. Death as a result of hepatitis was reported in 0.5% of those with hepatitis A, 1.4% of those with hepatitis B and 2.3% of those with non-A, non-B hepatitis.
A virus thought to be the cause of non-A, non-B hepatitis was identified by researchers of the Food and Drug Administration in 1984, but has not been confirmed by other investigators.
Bacterial Meningitis
An estimated 15,000 to 20,000 cases of bacterial meningitis are reported each year in the U.S. Despite effective therapy, approximately 8% of meningitis infections result in death and 20% result in residual neurologic damage. The true estimated annual incidence of meningitis of all etiologies is 229,000.
Almost 50% of bacterial meningitis cases are caused by Haemophilus influenzae b. Other meningitis-causing bacteria include Neisseria meningitidis, and Streptococcus pneumoniae.
Nosocomial Infections
Between 5% and 6% of hospitalized patients develop nosocomial infections. These infections result in nearly 12 million days of prolonged hospitalization and cost nearly $3.5 billion a year.
The National Nosocomial Infections Study (NNIS) reported an overall rate of nosocomial infections of 33.5 cases per 1,000 discharges in 1984.
The NNIS study listed the urinary tract as the site with the highest rate of infection (12.9 cases per 1,000 discharges) followed by surgical wounds (5.6), lower respiratory infections (6.0), cutaneous infections (1.9), primary bacteremia (2.5) and other (1.9).
A pathogen was identified in 84% of the nosocomial infections reported in the above study. 86% of the identified pathogens were aerobic bacteria, 2% anaerobic bacteria, 8% fungi and 5% viruses, protozoa and parasites.
Of nosocomial infections recorded in the NNIS study, approximately 0.7% were reported to have caused death, and 3.1% were reported to have contributed to death.
Public and Professional Awareness
Reye’s Syndrome and Aspirin
In 1981, CDC reported an association between Reye’s syndrome (RS) and use of salicylates (aspirin) during antecedent illness. In 1982, the Surgeon General advised against the use of salicylates in children with varicella or influenza.
A 1983 survey in Houston showed that 42% of parents knew about the association between aspirin and RS. A 1985 study revealed that 53% of parents surveyed knew that aspirin should not be used by children with flu or chicken pox and 40% could spontaneously name Reye’s syndrome as the reason.
In the three studies cited above, aspirin use during flu-like illness in children decreased from 69% in 1981 to 34% in 1983 to 16% in 1985.
In 1985, the reported incidence of Reye’s syndrome was much lower than in any previous year since surveillance was initiated. In 1986, despite high levels of influenza B nationwide, the incidence of Reye’s syndrome has remained unusually low.
Toxic Shock Syndrome
6% of high school females in 1983 survey had not heard of toxic shock syndrome. Another survey showed that 21% of college females changed menstrual products after learning about toxic shock syndrome.
One industry analyst claims that the external pad market has increased from 55% of sales in 1977 prior to awareness to toxic shock syndrome to close to 70% in 1985.
Service Delivery
Antibiotic Usage
The most frequently prescribed class of therapeutic drugs in the U.S. in 1981 was antibiotics, with 182.0 million prescriptions written, representing 13% of the entire prescription drug market.
According to the National Prescription Audit, the 6 most commonly prescribed antibiotics in 1982 were erythromycin (34.5 million prescriptions), amoxicillin (26.2 million), penicillin V/VK (23.4 million), tetracycline (18.5 million), ampicillin (18.5 million) and sulfamethoxazole (16.2 million).
In 1982, total expenditures for anti-infective drugs exceeded expenditures of any other therapeutic class of drugs. Drugstore costs for antiinfectives were $873.0 million and hospital costs were $1,009.3 million for a total of $1,882.3 million in 1982. Over one third of hospital drug expenditures were for anti-infectives in 1982.
Hospitalizations for Pneumonia
In 1983 in the U.S., 837,000 patients were discharged from hospitals with the diagnosis of pneumonia, for a rate of 3.6 persons with pneumonia discharged per 1,000 population. The average length of hospital stay for those with pneumonia in 1983 was 8.0 days. A total of 6.7 million hospital days of care were provided to those with pneumonia in 1983.
Prevention Estimates
A special report prepared by the CDC on prevention of infectious diseases estimates that 135 million infections, 63,000 deaths and $3.1 billion in direct costs are currently being prevented annually.
The same study estimates that a broader application of currently or soon-to-be available interventions could result in the prevention of an additional 56 million infections, 80,000 deaths and $1.3 billion in direct costs.
Significant Trends
Hepatitis
The incidence of hepatitis A has declined from a peak of 59,606 cases in 1971 to 22,040 cases in 1984 and a provisional figure of 22,959 cases in 1985. The incidence of hepatitis B has steadily increased since 1966 when it became a separate nationally notifiable disease (with 1,497 cases) to 1984 when 26,115 cases were reported and 1985 when a provisional 26,316 cases were reported. Since 1983, hepatitis B has been more commonly reported than hepatitis A in the U.S.
Malaria
The number of reported cases of malaria in the U.S. increased from 72 in 1960 to 3,051 in 1970 as a result of returning Vietnam veterans. After declining to about 300 cases per year in the mid-seventies, another increase occurred in 1980 when 2,062 cases of malaria were reported as a result of foreign immigration.
Poliomyelitis
From 1974 through 1984, an average of 11.3 cases of paralytic poliomyelitis were reported per year. Of the 90 cases of paralytic poliomyelitis reported from 1977-1983, 77% were endemic, 11% epidemic (all in 1979), 6% imported and 7% immunodeficiency-related. Of the 69 cases of endemic polio, 60 were among vaccinees or vaccine contacts.
Tuberculosis
From 1975 through 1978, the average annual decrease in reported tuberculosis cases was 5.7%. From 1978 through 1981, when there was a large influx of Southeast Asian refugees, the average decline was 1.4%. The average decline of 6.7% from 1982 to 1984 indicated that the previous downward trend had resumed. The 2.0% decline in 1985 represents another slowing of this trend.
Reasons for the relatively small decline in tuberculosis cases in 1985 are not fully known, but may be related to tuberculosis occurring in persons with human immunodeficiency virus (HIV).
Salmonellosis
From 1976 to 1983, the incidence rate of reported salmonellosis has increased 76% from 10.74 cases per 100,000 in 1976 to 18.91 cases per 100,000 in 1983. 40% of salmonellosis cases with reported age in 1983 affected children under 5 years old; however, the rate increases have occurred primarily among the older age groups. The cause(s) of the increase is (are) unknown.
Hospitalizations for Pneumonia
The number of non-Federal, short-stay hospital discharges for the diagnosis of pneumonia increased from 3.5 per 100,000 in 1979 to 3.6 per 100,000 in 1983. The average length of stay for a person with pneumonia remained 8.0 days.
Reye’s Syndrome
In the period 1981-1983, the reported incidence of Reye’s syndrome decreased, reflecting a decrease in the number of reported cases in children under 10 years of age and in the total number of varicella-associated cases.
Legionellosis
852 cases of Legionnaire’s Disease were reported to the CDC in 1983, for a rate of 0.43 per 100,000 population. This represents the highest number and rate of cases since legionellosis became a notifiable disease in 1976. Establishing the diagnosis of legionellosis is difficult and underreporting probably exists. An estimated 75,000 cases of symptomatic illnesses caused by legionella actually occur each year in the U.S.
