Rickards Invitational — Disease Detectives

U.S. Air Force basic training takes place at Joint Base San Antonio-Lackland in San Antonio, Texas. Trainees are organized into rolling military units averaging 900 entering and graduating trainees per week, with each unit further divided into groups of approximately 52 trainees. Trainees are assigned to specific dormitories, which typically house 50–60 persons, sleeping in beds that alternate head directions, creating a foot-to-head orientation in the bay. Trainees arrive weekly and undergo a standardized 7.5-week basic military training (BMT) curriculum organized by week of training, resulting in training activities and associated exposures that are typically consistent for each class.

To prevent invasive meningococcal and streptococcal disease outbreaks, all trainees receive quadrivalent meningococcal (Menveo) vaccine within 72 hours of arrival and a single dose of penicillin G benzathine injectable suspension, respectively, within 7 days of arrival (1). Penicillin allergic trainees receive weekly oral azithromycin to prevent streptococcal disease during BMT.

In February 2025, two cases of Neisseria meningitidis bacterial conjunctivitis were identified in otherwise healthy basic military trainees at Joint Base San Antonio-Lackland in San Antonio, Texas; an investigation was conducted to identify the source of the outbreak and to make treatment recommendations. Ultimately, 41 cases of N. meningitidis conjunctivitis and 32 cases of Haemophilus species conjunctivitis were identified among 11,797 trainees.

People spread meningococcal bacteria to others by sharing respiratory and throat secretions (saliva or spit). Generally, it takes close or lengthy contact to spread the bacteria.

The 41 confirmed cases of N. meningitidis conjunctivitis occurred in trainees in 37 unique BMT groups. During this period, men constituted 78% of the BMT population but accounted for 90% of the N. meningitidis cases. Among trainees with confirmed N. meningitidis conjunctivitis, 33 (80%) reported an antecedent upper respiratory infection, 27 people had cough, and 22 people had a sore throat. Overall, 35 (85%) patients had unilateral eye involvement.

Assume all confirmed cases are actual cases.

For questions 44-47, assume that everyone has an equal probability as everyone else of contracting disease given an exposure, and everybody has an equal level of exposure to the disease. Assume further the disease has no incubation period.

The following is pulled from the same case study.

“Whole genome sequencing of isolates from the first two cases suggested that the organism was unencapsulated (nongroupable) and that the cases were related.”

On February 5, 2025, a case of N. meningitidis bacterial conjunctivitis was identified in an otherwise healthy BMT trainee who had experienced 2 days of mucopurulent ocular discharge; the trainee had no known exposure to N. meningitidis. Although the symptoms initially suggested viral conjunctivitis, the copious unilateral discharge led the health care provider to culture the exudate, which was positive for N. meningitidis 6 days later.

Microbial isolates were tested and identified by Vitek 2 (bioMerieux). On February 21, a second trainee (from a different training unit) was also evaluated for unilateral copious mucopurulent ocular discharge associated with periocular edema without corneal involvement.

The culture of the exudate from this trainee’s eye was positive for N. meningitidis, raising concern about potential cases of invasive meningococcal disease. An investigation was initiated to identify additional cases, determine the risk for invasive meningococcal disease, and describe the patients and evaluate their response to treatment.

Suppose that the epidemiologists trace back all the cases, and find out that many of the cases are linked back to a certain place. Suppose further that this place is my house.

Consider the following table that I made up.

(My house is very spacious.)

There is an outbreak of Rickardsitis disease, and you have been assigned to investigate. To learn more about Rickardsitis, you look at past epidemiology studies on the disease. The data below is taken from a small town (population size 250) where there were 185 new cases of TQD over November. A pharmaceutical company called Invitationals Incorporated has developed a test to detect Rickardsitis. Here are the results of the evaluation study.

Using the table calculate the following values to the nearest hundredth.

Huzzah! Invitationals Inc. has also crafted a vaccine for Rickardsitis, to ensure that it works they ran a trial with some getting a vaccine dose others getting a placebo with the result below

For Rickardsitis, the transmissivity is .5, amount of people contacted per day on average is 25, and an individual on average is infected for 3 days.

The following case study is completely made up, any resemblance to real life figures or events is coincidental.

Dr. Imogen Vale, a senior field epidemiologist at the Department of Environmental Health, was called to investigate an unusual rise in chronic fatigue and skin irritation among urban gardeners in Brookmere City. The condition, later termed Blight Fever, presented with mild fevers, weakness, and a faintly luminescent rash visible under UV light. Concern escalated when local physicians noticed a pattern: nearly all affected gardeners worked in one of three community greenhouses that had recently switched to a new soil additive called EcoBloom X, designed to improve soil nitrogen retention.

To determine whether EcoBloom X was linked to Blight Fever, Dr. Vale and her team identified all active gardeners in the three greenhouses and recorded whether they had developed Blight Fever within three months of EcoBloom X’s introduction. They also measured each gardener’s level of exposure to the additive, categorizing them as high, medium, or low exposure based on hours spent handling treated soil. A blood test was later developed to detect a biomarker called BF-α, suspected to be associated with the illness.

Dr. Vale’s team followed gardeners, observing who developed Blight Fever over time while documenting their baseline exposures and environmental factors such as greenhouse ventilation and humidity. Participants were contacted biweekly for symptom monitoring and lab testing. While this design provided valuable incidence data, the project required significant logistical coordination and funding, and many participants dropped out midway, citing time constraints and fatigue.

Here are two tables you will need

Table 1: Ecobloom x Exposure and Incidence of Blight Fever

Table 2: BF-α Diagnostic Test Results Compared to Clinical Diagnosis