Foodborne outbreak among 4 families in Taif city, Saudi Arabia, July 2006

On the morning of July 27th 2006, several cases complaining of gastrointestinal symptoms of diarrhea, vomiting, abdominal pain and fever, presented to King Faisal hospital in Taif city. They belonged to one extended family. A team was formed from the preventive medicine department in Taif directorate, to confirm the occurrence and extent of this food poisoning outbreak, to determine the source of the outbreak, and to suggest recommendations to prevent similar outbreaks.

A retrospective cohort study was conducted to identify food items and other contributing factors. The extended family consisted of the nuclear families of 4 brothers living in 4 separate but adjacent houses. They denied sharing any meal that night or having any similar medical episode before that night. They had dinner at 10:00 pm that night each family separately. At about 2:00 am several members from each family started to experience gastroenteritis like symptoms then were taken to hospital.

The total family members were 64, 24 (37.5%) belonged to the 1st family, 23 (35.9%) the 2nd family, 10 (15.6%) the 3rd family, and 7 (10.9%) to the 4th family. Their ages ranged from 3-57 years (mean 19.4, median 15); 59 (92.2%) were Saudi, 43 (67.2%) were females.

Thirty-nine (60.9%) family members were ill, the majority developed diarrhea (97.4%), 2 had bloody diarrhea, 79.5% had fever, 71.8% abdominal pain, and 46.1% vomiting. Abdominal pain was the first symptom that appeared in 15 (38.5%), followed by fever in 14 (35.9%), then diarrhea 10 (25.6%). Patients experienced symptoms of gastroenteritis at 2:00 am July 27th 2006, up to 10:00 pm of the same day. The mean incubation period was 10 hours; median 2 hours, range 2-24. The Epidemic curve suggested a common point source outbreak (Figure 1).

Out of food items served for dinner for the 4 families, raw milk, which was shared among the four families, was significantly associated with the illness (RR=5.45, 95% CI =1.9-15.6). Other food items such as bread (RR =1.34, 95% CI = 0.88€”2.02), vegetables (RR=1.25, 95% CI=0.68-2.28) were not statistically significant.

Twenty individuals were admitted into hospital. Of those, a 14 year old girl was admitted to ICU with kidney impairment and hypotension but recovered shortly and was discharged after 1 week. Also, a 22 year old mentally retarded male with cerebral palsy since birth died after 3 days of onset.

Both blood and stool specimens were negative for the 20 patients who had been hospitalized. No food samples had been taken from food remnants of the suspected dinner, but 2 samples of the raw milk were taken and were sent to the Public Health laboratory in Makkah, and to King Abdulaziz University College of Medicine laboratory in Jeddah. Both came positive for E-coli.

Foodborne diseases outbreaks are recognized by the occurrence of illness within a usually short but variable period of time, among individuals after consuming a food in common. They can be divided according to etiology into 4 groups: bacterial, viral, parasitic, and chemical. The time of onset of symptoms may range from under 1 hour to over 48 hours of consuming the contaminated food. The incubation period of the illness can give a clue to the responsible causative agent.[1]

Escherichia coli (E. coli) are one of the main species of bacteria living in the lower intestines of mammals, where they are abundant. The E. coli strain O157:H7 is one of hundreds of strains of the bacterium that causes illness in humans. They produce a toxin very similar to that seen in dysentery. O157:H7 is further notorious for causing serious, life threatening complications such as Hemolytic Uremic Syndrome.[2]

Severity of the illness varies considerably; it can be fatal, particularly to young children, the elderly or the immunocompromised, but is more often mild. E. coli can harbor both heat-stable and heat-labile enterotoxins. The latter, is highly similar in structure and function to Cholera toxin, preventing intestinal cells from absorbing water, causing diarrhea.[3,4]

Symptoms of E. coli include severe stomach cramps and diarrhea (sometimes bloody), fever and vomiting. Most patients recover within ten days.[4]

The clinical, laboratory, and epidemiological data point to E-coli as the most likely causative organism of this outbreak. This is illustrated by the fact that it was isolated from the 2 subsequent samples of raw milk. The clinical picture with predominance of diarrhea (over 97%), with 2 cases with bloody diarrhea, and presence of fever 79%, is compatible with E-coli infection. The fact that one case had similar symptoms to Hemolytic-Uremic syndrome, and the death of the mentally retarded male are both characteristic of infection with certain strains of E-coli.

Consumption of the unpasteurized the raw milk was the most important factor that led to this outbreak. Health education is recommended to discourage people from consuming unpasteurized raw milk.