Common-source outbreaks

Fig. 16.2 Incidence pattern for common-source outbreaks of infection where the source persists ( ) and where it is short-lived ( ).

G. A common-source outbreak of fulminant hepatitis B in a hospital. 

Common source outbreaks are characterized by a sharp onset of reported cases over the course of a single incubation period and relate to a common experience of the infected individuals. The number of... 

MacLean ID, Arthur JR, Ward BJ, Gyorkos TW, Curtis MA, Kokoskin E (1996) Common-source outbreak of acute infection due to the North American Uver fluke Metorchis conjunctus. Lancet 347(8995) 154-158... 

Engleberg NC, Morris JG, Lewis J, McMillan JP, Pollard RA, Blake PA. Ciguatera fish poisoning a major common-source outbreak in the U.S. Virgin Islands. Ann Int Med 98 336-337, 1983. 

Frenette C, MacLean JD, Gyorkos TW. A large common-source outbreak of ciguatera fish poisoning. JIrtfecDis 158 1128-1131, 1988. 

Common-source outbreak An epidemic that arises from contact with contaminated substances. 

Bassett D.C. J. (1971) Causes and prevention of sepsis due to Gram-negative bacteria common sources of outbreaks. ProcR SocMed, 64, 980-986. 

Koopmans, M., Vennema, H., Heersma, H., van Strien, E., van Duynhoven, Y., Brown, D., Reacher, M., and Lopman, B. (2003). Early identification of common-source foodbome virus outbreaks in Europe. Emerg. Infect. Dis. 9,1136-1142. 

Those in close contact with an HAV-infected person, ail staff and attendees of daycare centers when HAV is documented, if involved in a common source exposure (such as a food-borne outbreak), classroom contacts of an index case patient, and schools, hospitals, and work settings where close personal contact occurred with the case patient. 

Clostridium novyi type A, a bacterium that was associated with serious infection during the two World Wars, killed 35 injecting heroin users in Britain and Ireland (49). Clostridium novyi type A is present in soil and dust and is a well-recognized cause of infection in sheep, cattle, and other animals. Contaminated batches of heroin from a common source were believed to be responsible for the recent outbreak. The bacteria were able to survive the process of preparation for injection. All recent cases occurred after intramuscular injection, which provides the requisite anerobic conditions for infection. This was the first time that this organism caused an outbreak of infection in drug injectors. In all, 74 cases with the same clinical features were reported. 

Outbreaks occurring simultaneously in different locations without a common source (Adapted by permission from Amon SS, et al. (36) Copyright 2001, American Medical Association. All Rights Reserved.)... 

Food borne diseases may effect a large number of persons in a short time from a common source. Previous outbreaks of Salmonellosis connted thousands of affected persons. Two representative examples of these ontbreaks are the following. In the USA in 1985 contamination of pasteurized milk with Salmonella typhimu-rium caused an outbreak of salmonella infection which affected 170,000 people. Another outbreak in China in 1991, contamination of hquid ice-cream with Salmonella enteritidis affected 224,000 people. 

Transmission of Salmonellosis occurs in the majority of cases by contaminated food. The most common sources are poultry, eggs, fruits, vegetables, dairy products and shellfish. Peanut butter has been also implicated in an outbreak of salmonellosis in the USA and powdered infant formula in two outbreaks with Salmonella enteric in infants in France. 

Human poisoning outbreaks by diarrheic toxins seem to be explosive, localized, and short-lived (holo-miantic outbreaks), given the very short incubation period (between 30 min and a few hours—3 h in DSP intoxication to 17 in AZA syndrome), which depends on the amount of toxin swallowed (shellfish toxic load and the amount of shellfish eaten), and the exposure to a common source. 

Numerous episodes have occurred in which humans have developed drug-resistant nontyphoid Salmonella infections that have been traced to animal sources (23). These bacteria can be transmitted to humans in food or through direct contact with animals. Antimicrobial resistance limits the tlierapeutic options available to veterinarians and physicians for the subset of clinical cases of nontyphoid Salmonella that require treatment. A recent example is a clone of Salmonella typhimurium DT 104 with chromosomally encoded resistance to ampicillin, tetracycline, streptomycin, chloramphenicol and sulfonamides, which has become increasingly common in humans in England and Wales since 1990 (24). Since 1992, only Salmonella enteritidis has accounted for more cases of human salmonellosis than Salmonella typhimurium DT 104 (25, 26). Multiresistant DT 104 has currently emerged in several European countries (27-29) outbreaks have been also reported in the United States in both cattle (30) and humans (31). 

---