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Year : 2015  |  Volume : 59  |  Issue : 2  |  Page : 109-114  

Mass chemoprophylaxis in control of pneumococcal pneumonia outbreak in a military training centre

1 Col Health and Senior Advisor Community Medicine, HQ 3 Corps (Med), c/o 99 APO, India
2 Officer Commanding, Station Health Organization, Ambala, India

Date of Web Publication25-May-2015

Correspondence Address:
Rajesh Kunwar
Col Health and Senior Advisor Community Medicine, HQ 3 Corps (Med), c/o 99 APO
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0019-557X.157526

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Background: Outbreaks of streptococcal pneumonia among young recruits in military training centers are well-documented. A significant outbreak of pneumonia occurred between November 19, 2011 and February 4, 2012 among the young recruits of a large training center located in Southern India. Objectives: The objective of this investigation was to identify the cause of the outbreak, to control the outbreak at the earliest, and to provide future strategies for containing such an outbreak. Materials and Methods: The outbreak was investigated using standard epidemiological methods so as to describe its epidemiology, to identify the causative organism, to guide the outbreak control efforts, and to provide future strategies for containing such an outbreak. Results: Over 2 months, 58 cases of pneumonia occurred among the recruits of the center, giving an attack rate of 4.81 cases per 1,000 person-months. Radiological positivity was found in 72.4% of the cases. Streptococcus pneumoniae (S. pneumoniae) was grown in all the three bronchoalveolar lavage (BAL) samples. The outbreak rapidly ended following prophylaxis with oral azithromycin. Conclusions: This outbreak of pneumococcal disease occurred in the setting of intense military training and a crowded environment. Oral azithromycin was found to be the suitable strategy for control of the outbreak.

Keywords: Mass chemoprophylaxis, outbreak investigation, pneumococcal pneumonia, training center

How to cite this article:
Kunwar R, Sidana N. Mass chemoprophylaxis in control of pneumococcal pneumonia outbreak in a military training centre. Indian J Public Health 2015;59:109-14

How to cite this URL:
Kunwar R, Sidana N. Mass chemoprophylaxis in control of pneumococcal pneumonia outbreak in a military training centre. Indian J Public Health [serial online] 2015 [cited 2022 Dec 4];59:109-14. Available from:

   Introduction Top

Outbreaks of acute respiratory illnesses (ARIs), including pneumonia, among the young recruits of military training centers are well documented. [1],[2],[3] Rapid gathering of persons from all over the country in crowded living conditions expose them to a variety of pathogens. Intense physical training and frequent intermingling contribute to increased ARI susceptibility, which often leads to outbreaks. [4],[5] Among ARIs, Streptococcus pneumoniae (S. pneumoniae) remains a leading cause of morbidity and mortality worldwide. [6] Though it is a leading cause of death among children, outbreaks due to S. pneumoniae have been frequently reported among the military trainees and the young recruits. [7],[8],[9]

An outbreak of pneumonia among the young military recruits of a large military training center occurred between November 19, 2011 and February 4, 2012. A team of authors investigated the outbreak. The objectives of this investigation were to identify the cause of the outbreak, to control the outbreak at the earliest, and to provide future strategies for containing such an outbreak.

   Materials and Methods Top


The center is located in South India, in a plain terrain with a river passing through it. It is spread out over a vast area. The posted strength of the center, at any given time, far exceeds the authorized strength. At the time of the outbreak, 6,743 individuals, including 5,100 recruits distributed in three training regiments (TRs), were posted against the authorized strength of 4,526. Two Regimental Medical Officers (RMOs) posted at he center and a service hospital located at a distance of approximately 2 km provide medical and health cover to the troops at the center and their families.

Outbreak: Case definition and data collection

A case of pneumonia was defined as a person posted at the center presenting with fever, cough whether productive or nonproductive, and chest pain showing lobar consolidation on x-ray chest posterior-anterior (PA) view between November 19, 2011 and February 4, 2012. A confirmed case was defined as a clinical case of pneumonia that was laboratory confirmed by the culture of S. pneumoniae or had a direct epidemiologic link to a laboratory confirmed case. All the other clinical cases were considered probable. [10]

All the cases were admitted to the nearest service hospital for further evaluation and management. An epidemiological case sheet was prepared, and information including the history of contact with a known case and clinical details were recorded. All the cases were subjected to sputum smear examination by Gram staining and sputum culture, in an effort to identify the causative organism. Bronchoalveolar lavage (BAL) samples were also collected from three such cases for the confirmation of the diagnosis. The samples for blood culture, and total and differential leukocyte counts were also collected from a suspect case before starting antibiotics. All the laboratory investigations, excluding that for influenza A (H1N1), were done in the service hospital. Blood samples for H1N1 were sent to a reputed laboratory. All the cases were line listed and analyzed by time, place, and person.

For finding out more cases all the individuals reporting with symptoms of cough and fever, with or without chest pain, to various emergency departments were subjected to throat swab/sputum smear examination and chest radiography. If found positive for either or both the tests, they were admitted to the hospital for further management.

In an effort to identify the index case and possible source of infection, the center was visited by the investigating team. Living conditions of the personnel and the environmental conditions were evaluated. The stakeholders were also interviewed for evidence suggestive of the possible source of the infection and the chain of transmission.

Case management

All the cases admitted to the hospital with typical signs and symptoms were treated with broad spectrum antibiotics without waiting for the confirmation of etiology. All of them responded well and recovered completely. No mortality was reported.

Outbreak control

In order to prevent the spread of infection among others, all the recruits were kept under surveillance. Individuals suffering from the abovementioned symptoms were segregated in a separate barrack and were not allowed to participate in any group activity. Every individual, whether sick or not, was advised to use a face mask all the time and was educated about cough hygiene and hand hygiene. Anyone with symptoms suggestive of pneumonia was asked to report sick and was admitted to the hospital on the basis of high clinical suspicion or chest radiograph, or if the throat swab/sputum smear examination was found to be positive for gram-positive diplococci.

Mass chemoprophylaxis with 500 mg of azithromycin tablet for 3 days followed by 500 mg once a week for 2 weeks was started, with effect from January 22, 2012. [11] Under the supervision of a medical officer, all the recruits and the permanent staff of the center were given the drug during their morning parade.

   Results Top

During the period from November 26, 2011 to February 4, 2012, a total of 58 recruits out of 5,100 were hospitalized with the diagnosis of pneumonia based on high clinical suspicion and/or radiological confirmation. These cases came from all the three TRs. The overall attack rate of pneumonia during this outbreak was 4.81 cases per 1,000 person-months.

Clinical features

As can be seen from [Figure 1], fever was the commonest symptom and was present in all the 58 (100%) cases. Fever was high grade and in most cases, was of 2-days duration at the time of hospitalization. Cough was present in 55 (94.8%) cases. Sputum, in a majority of the cases, was mucopurulent and was rusty in eight (13.8%) cases. Pleuritic chest pain associated with shortness of breath was present in 49 (84.5%) cases. The respiratory rate varied between 20 breaths per min and 26 breaths per min, with a mean of 22 breaths per min. Headache and vomiting were seen in nine (15.5%) cases. All these cases were hospitalized and treated with levofloxacin. All the cases recovered within 7 days. No fatality was reported.
Figure 1: Bar diagram showing distribution of symptoms among the cases admitted with pneumonia

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Descriptive epidemiology

The first case of pneumonia was admitted on November 26, 2011. Thereafter, the frequency of cases kept on increasing. Initially, two to three cases were reported per week till December 17, 2011, which was followed by seven to nine cases till January 7, 2012, and 11-12 cases per week thereafter. A sharp fall in the curve was noted after mass chemoprophylaxis with azithromycin. The course of the outbreak is indicative of a propagated type of epidemic, which is evident from [Figure 2]. Distribution of cases according to the place of residence in the center is shown in the spot map [Figure 3]. Clustering of cases, as seen in the spot map, is in proportion to the number of recruits staying in those areas. The remaining part in the spot map indicates office buildings, classrooms, and outdoor training area, and recreational area. All the 58 cases occurred among the young male recruits aged 19-22 years, in various phases of their training cycle. All of them were apparently healthy and did not suffer from any risk factor before falling sick. None of the permanent staff was found to be affected during the period of the outbreak.
Figure 2: Epidemic curve
Note: The fi rst case of pneumonia was admitted on the last day of the week ending on November 26, 2011. Thereafter, the frequency of cases kept increasing. A sharp fall in the curve was noted after mass chemoprophylaxis with azithromycin was started on January 22, 2012, i.e., in the 10th week

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Figure 3: Spot map showing distribution of cases according to the place of their living in unit area
Note: The map is not to scale. Arbitrary boundaries have been made between various subunits of the training center. Clustering of cases is seen in the living area.

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Ecological factors

In the center, the recruits stay in independent barracks and pucca accommodation. During the period of outbreak, on the advice of the health authorities the recruits were also put up in makeshift accommodations and it was ensured that there was no overcrowding. However, all the recruits do mix among themselves during meals, training, sports, and recreational activities. They also undergo frequent short periods of outdoor training, which facilitates the spread of airborne infection.

The climatic condition was found to be in a comfortable zone. The days were warm with a chill in the nights and early mornings. The average minimum and maximum temperatures varied from 14°C to 15°C and 24°C to 27°C, respectively. There had been no rain in the recent past, and the relative humidity varied from 20% to 40%.

Laboratory findings

All the cases had polymorphonuclear leukocytosis, which indicated a bacterial infection. Sputum samples of 48 cases (82.76%) were found positive on Gram staining for diplococci, but no growth was observed in any of these samples in 48 h. However, S. pneumoniae was grown on all the three BAL specimens. Of the 58 patients admitted with pneumonia, only 42 (72.4%) had radiological findings [Figure 4]. Three (7.14%) cases had multilobar involvement and five (8.62%) had a pleural effusion. No one had intrathoracic adenopathy or cavitary lesions on a radiograph. S. pneumoniae growth was observed only in BAL specimens, thus confirming the diagnosis in 5.17% of the cases.
Figure 4: Chest X-ray showing wedge-shaped consolidation in the left lung

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Outbreak control

Following the administration of mass prophylaxis from January 22, 2012, the number of cases declined rapidly. Only two cases were admitted on January 22, 2012 and one case on January 23, 2012. No case occurred during the follow-up period till February 4, 2012.

The clinical findings, nature of the epidemic curve, i.e., propagated epidemic and radiological findings, demonstration of diplococci in sputum samples, and growth of S. pneumoniae in BAL specimens indicated that the present outbreak of pneumonia was because of S. pneumoniae. The outbreak occurred due to direct/indirect contact with other cases/airborne transmission. Apparently, overcrowding that was reduced by the time investigation was taken up, severe physical exertion, and intermingling of recruits during various training and recreational activities resulted in the spread of infection. The infection was probably introduced by one of the recruits. The outbreak dramatically subsided with mass chemoprophylaxis.

   Discussion Top

The attack rate of pneumonia (4.81 cases per 1,000 person-months) in the military training center far exceeded the attack rate of 0.39 cases per 1,000 person-months in the previous years and, thus, established an outbreak. Clinical features of the cases associated with complete recovery within 5-10 days and isolation of S. pneumoniae, which is the predominant causative organism and accounts for about two-third of all the cases of bacterial pneumonia, confirmed the causative organism. [12],[13],[14]

The present outbreak of pneumonia was typical of S. pneumoniae infection, highlighting the proneness, like in other countries, of young military recruits undergoing training at various centers in our country too. A similar outbreak in a military training facility of California in the US had shown an attack rate of 16 cases per 1,000 person-months and a radiological positivity of 78%, compared to our attack rate of 4.81 cases per 1,000 person-months and radiological positivity of 72.4%. [15] While the radiological findings were found to be similar, difference in the attack rates may be explained by the differences in climatic conditions. The outbreak investigation also brought out that routine sputum and blood culture in cases of S. pneumoniae may not succeed in clinching the diagnosis.

Controlling the outbreak was found to be challenging. Routine measures like segregation, isolation, reduction of overcrowding, use of face masks, and cough hygiene and hand hygiene, which were found to be effective in controlling such outbreaks on earlier occasions, were not found to be useful. [16] Thus, other options had to be explored.

Pneumococcal polysaccharide vaccine has been recommended for the prevention of pneumococcal disease and has been used in various outbreaks, along with antibiotics for its containment. [8],[9],[17],[18] But these vaccines only reduce the incidence of invasive pneumococcal disease and do not appear to reduce the incidence of pneumonia or death in old age. [12],[19] Benzathine penicillin has also been effectively used to prevent acute respiratory diseases and contain the outbreak. [20] A subsequent randomized field trial showed that oral azithromycin is an effective alternative prophylaxis to benzathine penicillin for military populations. [21] A study of pneumonia outbreak associated with group A Streptococcus at a military training facility in San Diego in California, the US recommended the need for surveillance and consideration of appropriate antibiotic prophylaxis among the particularly high-risk populations. [15] An outbreak of pneumococcal pneumonia in a cohort of Ranger students at Fort Benning in 1999 was controlled by mass azithromycin treatment. [22] In another outbreak of pneumococcal pneumonia among the military recruits of a training center in South India in 2002, reduction of overcrowding and administration of low dose of erythromycin or azithromycin for 5 days was found suitable for controlling the outbreak. [11] In case of the present outbreak, mass chemoprophylaxis with azithromycin alone was used to control it and it was found to be very effective.

The present outbreak investigation provided food for thought. The first few cases, which were considered sporadic cases, led to the beginning of the outbreak when routine preventive actions, including reduction of overcrowding, were taken. But, this could not check the spread of this airborne infection because of the close interaction of the recruits during training and recreational activities. The outbreak was controlled only after mass chemoprophylaxis with azithromycin was started. Usefulness of mass chemoprophylaxis with azithromycin in controlling pneumococcal pneumonia outbreak over routine preventive measures in the case of a training center needs to be deliberated and studied by a randomized controlled trial.

As far as mass chemoprophylaxis with azithromycin is concerned, the time of starting the chemoprophylaxis and its dose has not been standardized. In a randomized controlled trial conducted in 2001-2002, Russian military trainees were randomized to one of the following three trial arms by the training group: azithromycin, 500 mg per week for 8 weeks (R1); azithromycin, 1,500 mg once at enrollment (R2); or no therapy (R3). During the 22 weeks of training, community-acquired pneumonia was diagnosed in 20.2% of 678 subjects in the R3 group, 8.6% of 508 subjects in the R1 group, and 10.3% of 507 subjects in the R2 group. Azithromycin prophylaxis was found to be effective in both the dose schedules. [23]

As a future strategy, in our opinion, mass chemoprophylaxis with 500 mg of azithromycin for 3 days, followed by 500 mg once a week for 2 weeks should be incorporated in all measures directed toward the control of pneumococcal pneumonia outbreak. It may be used as a supplement to routine preventive measures and should be initiated once the outbreak is established.

Limitations of the Study

Our investigation was subject to certain limitations too. It began after majority of the pneumonia cases had occurred. So we relied, in part, on diagnostic tests performed by the treating clinician who intended to treat the case rather than finding the cause of the outbreak. Many of those who had recovered and were away on sick leave could not be reached for the interview. Apart from this, the investigation was undertaken as part of a public health response and the aim was to contain the outbreak. Hence, the healthy recruits, who would have acted as controls, were not subjected to any investigation.

   Conclusion Top

It has been clearly brought out by the present outbreak investigation that routine sputum culture is unlikely to isolate S. pneumoniae during outbreak situations and routine control measures are unlikely to succeed in containing the outbreak. Mass chemoprophylaxis with azithromycin was found to be the most effective measure for the control of the outbreak by us. It may prove to be the future strategy for control of all pneumococcal pneumonia outbreaks.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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