Tuberculosis in association with travel

Association of High-Speed Rail and Tuberculosis Transmission in Newly Integrated Regions: Quasi-Experimental Evidence from China

Objectives: The spread of tuberculosis (TB) is related to changes in the social network among the population and people’s social interactions. High-speed railway (HSR) fundamentally changed the integrated market across cities in China. This paper aims to examine the impact of HSR on TB transmission in newly integrated areas.

Methods: By exploiting the opening and operation of the first HSR in Sichuan province as a quasi-natural experiment, we have collected and used the economic, social, and demographic data of 183 counties in Sichuan province from 2013 to 2016.

Results: The new HSR line is associated with a 4.790 increase in newly diagnosed smear-positive TB cases per 100,000 people among newly integrated areas. On average, an additional increase of 34.178 newly diagnosed smear-positive TB cases occur every year in counties (or districts) covered by the new HSR.

Conclusion: HSR development has significantly contributed to the transmission of TB. The public health system in China needs to pay more attention to the influences of new, mass public transportation.

Tuberculosis and mass gatherings-opportunities for defining burden, transmission risk, and the optimal surveillance, prevention, and control measures at the annual Hajj pilgrimage

Tuberculosis (TB) is now the most common infectious cause of death worldwide. In 2014, an estimated 9.6 million people developed active TB. There were an estimated three million people with active TB including 360000 with multidrug-resistant TB (MDR-TB) who were not diagnosed, and such people continue to fuel TB transmission in the community. Accurate data on the actual burden of TB and the transmission risk associated with mass gatherings are scarce and unreliable due to the small numbers studied and methodological issues. Every year, an estimated 10 million pilgrims from 184 countries travel to the Kingdom of Saudi Arabia (KSA) to perform the Hajj and Umrah pilgrimages. A large majority of pilgrims come from high TB burden and MDR-TB endemic areas and thus many may have undiagnosed active TB, sub-clinical TB, and latent TB infection. The Hajj pilgrimage provides unique opportunities for the KSA and the 184 countries from which pilgrims originate, to conduct high quality priority research studies on TB under the remit of the Global Centre for Mass Gatherings Medicine. Research opportunities are discussed, including those related to the definition of the TB burden, transmission risk, and the optimal surveillance, prevention, and control measures at the annual Hajj pilgrimage. The associated data are required to develop international recommendations and guidelines for TB management and control at mass gathering events.

Review of bioaerosols in indoor environment with special reference to sampling, analysis and control mechanisms

Several tiny organisms of various size ranges present in air are called airborne particles or bioaerosol which mainly includes live or dead fungi and bacteria, their secondary metabolites, viruses, pollens, etc. which have been related to health issues of human beings and other life stocks. Bio-terror attacks in 2001 as well as pandemic outbreak of flue due to influenza A H1N1 virus in 2009 have alarmed us about the importance of bioaerosol research. Hence characterization i.e. identification and quantification of different airborne microorganisms in various indoor environments is necessary to identify the associated risks and to establish exposure threshold. Along with the bioaerosol sampling and their analytical techniques, various literatures revealing the concentration levels of bioaerosol have been mentioned in this review thereby contributing to the knowledge of identification and quantification of bioaerosols and their different constituents in various indoor environments (both occupational and non-occupational sections). Apart from recognition of bioaerosol, developments of their control mechanisms also play an important role. Hence several control methods have also been briefly reviewed. However, several individual levels of efforts such as periodic cleaning operations, maintenance activities and proper ventilation system also serve in their best way to improve indoor air quality.

Population dynamics and tuberculosis: a cross sectional study of an overlooked disease in Saudi Arabia

BACKGROUND

International travel, migration and human population movements facilitate the spread of tuberculosis (TB).

OBJECTIVE

To study the impact of poorly screened expatriates working in Saudi Arabia on the local incidence of TBs.

PATIENTS AND METHODS

This cross sectional study was carried out in the Chest Disease Hospital, Taif. All confirmed cases of TB from June 2009 to May 2010 admitted to the hospital were enrolled. Inclusion criteria were diagnosed cases of TB (pulmonary & extra-pulmonary) in patients between the ages of 14 to 65 years. Patients with HIV and coexistent malignancies were excluded. The age, gender and ethnic group of each patient was recorded, and patients were divided into two groups. Of the two groups, Group A consisted of Taif residents and group B of patients referred from other cities in the country.

RESULTS

Of the 686 cases studied, 370 (54%) were Saudi nationals (Group A = 80 & Group B = 290) and 316 (46%) cases were from other countries. Males outnumbered females and most of the patients were aged 20 to 29 years. The number of cases from the areas close to the pilgrimage sites, i.e. Makah (233) and Jeddah (275), outnumbered those in Taif (110).

CONCLUSIONS

Our study identifies an increased prevalence of TB cases in areas close to the pilgrimage (Group B). The higher proportion of non-Saudi TB patients in group B is most likely explained by the higher number of poorly screened illegal expatriates in the region.

Tuberculosis in Saudi Arabia: prevalence and antimicrobial resistance

Tuberculosis is a serious contagious disease caused by Mycobacterium tuberculosis and is endemic in many countries. Over the past two decades, there has been an increase in the number of multidrug-resistant TB and extensively drug-resistant TB cases around the world. As in many countries, TB is common in Saudi Arabia. The disease is particularly relevant in the Kingdom because of its population dynamics including a large number of resident expatriates mainly from TB endemic regions and the influx of millions of pilgrims to the country each year during the Hajj and Umrah seasons. This review investigates the prevalence and antimicrobial resistance among M. tuberculosis isolates from Saudi Arabia, highlighting the variations in rates in different geographical areas with particularly high rates in the main cities and regions hosting the annual pilgrimage. The review also refers to the measures needed to prevent and control TB transmission in the country.

Risk of transmission of airborne infection during train commute based on mathematical model

Objective

In metropolitan areas in Japan, train commute is very popular that trains are over-crowded with passengers during rush hour. The purpose of this study is to quantify public health risk related to the inhalation of airborne infectious agents in public vehicles during transportation based on a mathematical model.

Methods

The reproduction number for the influenza infection in a train (R_A) was estimated using a model based on the Wells-Riley model. To estimate the influence of environmental parameters, the duration of exposure and the number of passengers were varied. If an infected person will not use a mask and all susceptible people will wear a mask, a reduction in the risk of transmission could be expected.

Results

The estimated probability distribution of R_A had a median of 2.22, and the distribution was fitted to a log-normal distribution with a geometric mean of 2.22 and a geometric standard deviation of 1.53, under the condition that there are 150 passengers, and that 13 ventilation cycles per hour, as required by law, are made. If the exposure time is less than 30 min, the risk may be low. The exposure time can increase the risk linearly. The number of passengers also increases the risk. However, R_A is fairly insensitive to the number of passengers. Surgical masks are somewhat effective, whereas High-Efficiency Particulate Air (HEPA) masks are quite effective. Doubling the rate of ventilation reduces R_A to almost 1.

Conclusions

Because it is not feasible for all passengers to wear a HEPA mask, and improvement in the ventilation seems to be an effective and feasible means of preventing influenza infection in public trains.

Giving TB wheels: Public transportation as a risk factor for tuberculosis transmission

Previous geospatial analysis of the well-defined Houston Tuberculosis Initiative (HTI) database identified an association between the use of city-bus transportation (inclusive of time onboard) and Tuberculosis (TB) incidence in Houston/Harris County census tracts (paper submitted). This paper is an extension of those findings. Contact investigations on school buses have reported a high rate of positive tuberculin skin tests in the persons traveling with the index case and have shown an association with bus ride duration. In Houston, city bus routes are veins connecting even the most diverse of populations within the metropolitan area. Among HTI participants, TB patients who reported weekly bus use were more likely to have demographic and social risk factors associated with poverty, immune suppression and health disparities. An equal proportion of bus riders and non-bus riders were cultured for Mycobacterium tuberculosis (MTB), yet 75% of bus riders were clustered with a mean cluster size of 50.14, indicating recent transmission, compared to 56% of non-bus riders (OR = 2.4, p < 0.001) with a mean cluster size of 28.9 (p < 0.01). Individual bus routes, including one route servicing the local hospitals, were found to be risk factors for endemic MTB clustered strains and the routes themselves geographically connect the census tracts previously identified as having endemic TB.

Tuberculosis in Saudi Arabia: can we change the way we deal with the disease?

Infection from Mycobacterium tuberculosis results in the death of three million people worldwide per annum of which an estimated one thousand are in Saudi Arabia. The WHO has set a target for successful treatment of 85% but Saudi Arabia is currently not meeting that target. We believe that the first step in improving the control of tuberculosis in Saudi Arabia is to improve and unify the standards of diagnostic services and laboratories responsible for tuberculosis. This paper reviews the current status and suggests possible improvements.

To BCG or not to BCG? Preventing travel-associated tuberculosis in children

With the rise in travel to countries with a high prevalence of tuberculosis (TB), the risk of travel-associated TB is of increasing concern. However, the use of Bacille Calmette-Guérin (BCG) vaccine for the prevention of travel-associated TB is a neglected area. We review and discuss national and international recommendations and guidelines for the prevention of travel-associated TB in children. Three children who developed travel-associated TB disease are described to illustrate that current recommendations, and in particular the use of pre-travel BCG immunisation, are inconsistent and controversial. The wide variation in recommendations reflects the paucity of data on the effectiveness of BCG immunisation and other preventive strategies in this setting. Until evidence-based guidelines can be produced, we believe that a low threshold for recommending BCG immunisation for travelling children is the safest strategy. A practical approach to deciding which children should be immunised with BCG prior to travel is presented.

Acute respiratory infections in a recently arrived traveler to your part of the world

Many acute infectious pulmonary diseases have incubation periods that are long enough for travelers to have symptoms after returning home to a health-care system that is not familiar with "foreign" infections. Respiratory infections have a relatively limited repertoire of clinical manifestations, so that there is often nothing characteristic enough about a specific infection to make the diagnosis obvious. Thus, the pathway to the diagnosis of infections that are not endemic in a region relies heavily on taking a thorough history of both itinerary and of specific exposures. One important caveat is that on occasion, the history of a recent trip creates an element of "tunnel vision" in the evaluating health-care provider. It is tempting to relate a person's problem to that recent trip; however, when evaluating recent returnees, it is always important to remember that the travel may have nothing to do with the patient's presentation. Recent travel may add diagnostic considerations to the list of possibilities, but an astute clinician must not disregard the possibility that the patient's illness has nothing to do with the recent trip.

Special infectious disease risks of expatriates and long-term travelers in tropical countries. Part II: infections other than malaria

A wide range of viral, bacterial, and protozoal diseases pose risk to long-term tropical travelers. Risk varies geographically and with lifestyle. For some infections, risk increases with duration of stay, coming to resemble that of the local population. Risk management strategies include vaccination, chemoprophylaxis, avoidance measures, and screening, where appropriate. Vaccination against hepatitis A and B, typhoid, and rabies is recommended for all long-term travelers to (sub-)tropical areas. Lowering of the vaccination threshold for Japanese encephalitis is suggested. Meningococcal disease is rare in travelers, but vaccination is safe and acceptable. The efficacy of Bacillus Calmette-Guérin (BCG) is uncertain; immunological testing avoids BCG's confounding of tuberculin testing. Diarrhea is common, and self-treatment may be recommended. Sexually transmitted infections including human immunodeficiency virus (HIV) are serious risks; education, screening, and HIV postexposure prophylaxis following involuntary exposure are recommended. Many infections are chronic or asymptomatic, and appropriate screening is recommended on return or after prolonged exposure.

Health risks at the Hajj

Annually, millions of Muslims embark on a religious pilgrimage called the "Hajj" to Mecca in Saudi Arabia. The mass migration during the Hajj is unparalleled in scale, and pilgrims face numerous health hazards. The extreme congestion of people and vehicles during this time amplifies health risks, such as those from infectious diseases, that vary each year. Since the Hajj is dictated by the lunar calendar, which is shorter than the Gregorian calendar, it presents public-health policy planners with a moving target, demanding constant preparedness. We review the communicable and non-communicable hazards that pilgrims face. With the rise in global travel, preventing disease transmission has become paramount to avoid the spread of infectious diseases, including SARS (severe acute respiratory syndrome), avian influenza, and haemorrhagic fever. We examine the response of clinicians, the Saudi Ministry of Health, and Hajj authorities to these unique problems, and list health recommendations for prospective pilgrims.

Airplanes and Infectious Disease

Air travel is associated with crowded conditions that can facilitate the transmission of airborne infectious diseases. The risk of contracting such diseases depends on the presence of an infected person who is shedding infectious particles and sufficient exposure of a sensitive person to achieve an adequate dose to cause disease. Proximity to the infectious person and the length of time spent near the person are the most important risks for contracting a disease. Ventilation patterns play a lesser role in disease transmission. Well-documented outbreaks of influenza, severe acute respiratory syndrome (SARS), and tuberculosis have occurred. Other common respiratory illnesses have probably also been spread via aircraft, but outbreaks remain unrecognized. Research on the spread of infectious disease in aircraft has focused on sampling for microorganisms in air (which has little relevance), and on the development of models to predict the risks for specific diseases.

High risk of Mycobacterium tuberculosis infection during the Hajj pilgrimage

INTRODUCTION

Annually more than 2 million pilgrims from all over the world attend the Hajj in Saudi Arabia. Overcrowding during this pilgrimage leads to a high risk of transmission of airborne infectious diseases. Tuberculosis (TB) is common among hospitalized pilgrims, but the overall risk of acquiring Mycobacterium tuberculosis infection during this pilgrimage is not known. We conducted a prospective study to assess the risk of M. tuberculosis infection among Hajj pilgrims.

METHODS

We measured the immune response to TB antigens using a whole-blood assay (QuantiFERON TB assay) prior to departure and 3 months after return from the Hajj pilgrimage.

RESULTS

Of 357 paired assays, 149 pilgrims were negative prior to the Hajj and 15 (10%) of these had a significant rise in immune response to TB antigens.

CONCLUSIONS

Pilgrims may be at high risk of acquiring M. tuberculosis infection during the Hajj. This has significant public health implications for TB control in countries with large Muslim populations.

Comparison of in vitro activities of ketolides, macrolides, and an azalide against the spirochete Borrelia burgdorferi

Two ketolides, three macrolides, and one azalide were tested in vitro against 17 isolates of the B. burgdorferi s.l. complex. As measured in micrograms per milliliter, activity was highest for cethromycin (MIC at which 90% of the tested isolates were inhibited [MIC(90)], 0.0019 micro g/ml) and telithromycin (MIC(90), 0.0078 micro g/ml). Electron-microscope analysis and time-kill studies also supported enhanced effectiveness of both ketolides.