Rubella outbreak among police cadet training forces during Hajj 1415 H

During the pilgrimage to Makkah in 1415 H (1995), an outbreak of rubella occurred among police cadets on a field training exercise. Ten police cadets were admitted into the Security Forces Hospital in Makkah where they were examined and interviewed. The patients came from the Training City Security Forces Training City (SFTC) in Riyadh. They all complained of mild fever, generalized rash, and post auricular and occipital lymphadenitis. We began an epidemiological investigation to identify the extent of and reasons for the outbreak.

There were 880 cadets accepted for training in 1995 at SFTC in Riyadh. They were divided into 3 groups: group A (299 cadets), group B (281 cadets), and group C (300 cadets). The groups lived in six different dormitories, groups A and B were housed in close proximity while group C was housed further away. Each group had nine different classrooms. They were served by a well-equipped dispensary which provided all medical services for cadets, officers, and their families.

We defined a rubella case as development of fever and rash with anti-rubella IgM detected in a cadet from SFTC from 25/10 to 15/12/15H. To find all possible rubella cases, we questioned cadets and reviewed outpatient registries for rashes among cadets in all Makkah hospitals and SFTC dispensaries in Riyadh. We determined the rubella vaccination history by questioning the rubella patients, and we then selected two controls for each case by a systemic random sample.

For seven weeks following the appearance of two rubella cases in Riyadh, 41 additional rubella cases developed (AR 49 per 1000), 21 occurred in Riyadh during routine classes (AR 24 per 1000), the second (22 cases) occurred in Makkah (AR 25 per 1000)(Figure 1).

We identified two index cases from two different groups (group A and B). Both index cases began to develop the illness on 25/10/15 H. They developed rubella two weeks after returning from vacation. The two index cases came from different regions (Al Baha and Al Jouf). From 15 to 21 days (median 18) after the onset of rubella in these two cadets, 22 cadets had onset of rubella in Riyadh SFTC. This cluster of rubella cases was followed by the second cluster in Makkah 16 to 21 (median 18) days later.

All three training groups were affected. Attack rates were similar in groups A and B, where the two index cases originated (70 and 60 per 1000 respectively), but lower in group C (17 per 1000). Rubella cases clustered by classroom (chi square 16.5, P value<0.05), and by dormitory (chi square 11.4, P value<0.05). Rubella patients during the first wave of the outbreak in Riyadh were more likely than unaffected cadets to occupy a bed adjacent to a primary case (risk ratio [RR] =5.5, P value < 0.05). Similarly, rubella patients during the second wave in Makkah were more likely than unaffected cadets to occupy a bed adjacent to a rubella patient during the first wave of the outbreak in the Riyadh SFTC dormitory (RR= 14.1, p < 0.0001). After the cases started to appear in

Makkah, mass vaccination with MMR was started (figure 1) for cadets and officers, and the follow up of SFTC

Most military recruits originate from different rural areas and so have had varied social exposure to communicable diseases. They may not have been given primary vaccinations, nor been exposed to infectious diseases.[1] The rubella outbreak that occurred in Makkah was actually the second wave of an outbreak that began in Riyadh. A sick leave of five days was given by the dermatologist to infected cadets in the first outbreak, but this was by no means sufficient two stop transmission in Riyadh. The source cases had returned from vacation from two different regions that did not experience a rubella outbreak or report rubella cases. During this Eid holiday, flights were full and airports were crowded. It is therefore likely that the source cases were infected while traveling by airplane or while waiting in airports.

The nature of the propagating cases in the epidemic curve, and of the clustering of cases in the same dormitories, and classrooms show that in this outbreak, the rubella infection was transmitted through close contact (person to person). Lack of rubella vaccination and a delayed response to early reports of rubella led to this outbreak which interfered with the cadets' training.

Rubella cases and suspected outbreaks should be reported immediately to the local health department. An accurate assessment of rubella elimination can be made only through aggressive case finding. Surveillance of rubella must be intensified. In this study a delayed response to early reports of rubella by Riyadh health officials led to the occurrence of the second wave of the outbreak in Makkah.

Propagating rubella outbreaks of this kind can be prevented. All SFTC cadets should have been immediately vaccinated against MMR when the first index had been identified. The goal of the rubella vaccination program is to prevent congenital rubella infection.[2] All girls aged 1014 years, and all rubella-susceptible females of childbearing age should continue to receive the rubella vaccine.[3] Medical military services should vaccinate cadets against MMR and other routine childhood diseases. This age group was not covered under the mandatory vaccination laws begun in 1983. Moreover, these cadets often come from rural areas where exposure to the natural infection is sporadic.