On January 21, a physician notified the New Mexico Department of
Health (NMDH) of a dramatic increase in acute gastroenteritis among
students at a small college in Las Vegas, New Mexico. Las Vegas is
city located in northern New Mexico [population estimate: 13,285]
and is the county seat of San Miguel County [population estimate:
27,760]. The physician reported examining hundreds of students with
a gastrointestinal illness at the college’s student health center
during the previous week. The majority of students reported having
abdominal pain and watery diarrhea of several days duration.
Typically, approximately 100 students were examined at the student
health center each day, the majority of whom presented with
upper-respiratory infections or injuries. On January 20 alone, over
200 students were examined at the student health center for
gastroenteritis. The NMDH later confirms that this is an outbreak
of cryptosporidiosis; this type of outbreak had last occurred 35
years ago. The incubation period of cryptosporidiosis is about 7
days.
Follow-up studies showed that based on water consumption
amounts, the infectious dose of cryptosporidium among the college
students was 132 oocysts, whereas among the nursing home patients
got infected consuming as little as one-twenty-fifth of the water
amount; indicating that they were infected by as few as 5
oocysts.
Why was there such a difference in the ID numbers in the two
patient populations?
Difference in immune capacities among patients.
The cryptosporidium found in the nursing homes must have
contained virulence genes whereas the cryptosporidium found in on
the college campus did not.
The college students drank more water and thus were exposed to
higher doses of oocysts.
They must have been different strains of cryptosporidium.