Sacred journeys and pilgrimages: health risks associated with travels for religious purposes

Abstract

Background

Pilgrimages and travel to religious mass gatherings (MGs) are part of all major religions. This narrative review aims to describe some characteristics, including health risks, of the more well-known and frequently undertaken ones.

Methods

A literature search was conducted using keywords related to the characteristics (frequency of occurrence, duration, calendar period, reasons behind their undertaking and the common health risks) of Christian, Muslim, Hindu, Buddhist and Jewish religious MGs.

Results

About 600 million trips are undertaken to religious sites annually. The characteristics vary between religions and between pilgrimages. However, religious MGs share common health risks, but these are reported in a heterogenous manner. European Christian pilgrimages reported both communicable diseases, such as norovirus outbreaks linked to the Marian Shrine of Lourdes in France, and non-communicable diseases (NCDs). NCDs predominated at the Catholic pilgrimage to the Basilica of Our Lady of Guadalupe in Mexico, which documented 11 million attendees in 1 week. The Zion Christian Church Easter gathering in South Africa, attended by ~10 million pilgrims, reported mostly motor vehicle accidents. Muslim pilgrimages such as the Arbaeen (20 million pilgrims) and Hajj documented a high incidence of respiratory tract infections, up to 80% during Hajj. Heat injuries and stampedes have been associated with Hajj. The Hindu Kumbh Mela pilgrimage, which attracted 100 million pilgrims in 2013, documented respiratory conditions in 70% of consultations. A deadly stampede occurred at the 2021 Jewish Lag BaOmer MG.

Conclusion

Communicable and NCD differ among the different religious MGs. Gaps exists in the surveillance, reporting and data accessibility of health risks associated with religious MGs. A need exists for the uniform implementation of a system of real-time monitoring of diseases and morbidity patterns, utilizing standardized modern information-sharing platforms. The health needs of pilgrims can then be prioritized by developing specific and appropriate guidelines.

Introduction

Most the world’s major religions are associated with pilgrimages and travel to religious sites, whether as an obligation, as spiritual upliftment or as affirmation of faith. There is not a standard definition for the term ‘religious tourism’, and we shall use it in the context of travel motivated by religious purposes. It is considered as the oldest form of tourism.¹ It is estimated that in 2022, out of a global population of close to 8 billion, 31.6% were Christians, 25.8% were Muslims, 15.1% Hindus, 6.6% Buddhists and 0.2% Jews, with 14.4% unaffiliated.²

According to the World Tourism Organisation estimates, 300 to 330 million travellers annually have a religious site as a destination, with ~600 million trips undertaken nationally or internationally.³ In 2018, 60% (>1 billion) of the 1.8 billion Indian domestic tourists travelled solely for religious purposes.¹ Saudi Arabia’s Vision 2030 projects an increasingly positive economic benefit from religious tourism as an alternative to oil.⁴ Mass gatherings (MGs) is defined by the World Health Organisation as ‘A planned or spontaneous event where the number of people attending could strain the planning and response resources of the community or country hosting the event’.⁵ MGs for religious reasons have been described since the prehistoric era in Stonehenge, England, ~9000 years ago.⁶

Pilgrimages and religious MGs may involve overcrowding, national and international movement of people that exposes individuals to the risk of communicable diseases,^7,8 environmental hazards arising from the effects of adverse weather conditions, transport-related hazards, stampedes and physical and mental stress that may be precipitated by the demands of the rituals, and exacerbation of pre-existing medical conditions.^9,10

This narrative review was performed in PubMed, Semantic Scholar, Academia and other databases for research publications, newspaper articles and books that provides an overview of some of the more well-known and frequently undertaken pilgrimages and religious MGs, frequency of occurrence, duration, calendar period, reasons behind their undertaking and the common health risks encountered. All manuscripts published in English and available in electronic format up to and including July 2024 were used. The focus of this manuscript is on commonly occurring and frequently published religious mass gatherings of the main religious denominations, and does not include all known religious MGs.

Christian pilgrimages

European/Asian pilgrimages

Christian pilgrimages occur on all continents except Antarctica. They encompass visits to the burial sites of Christian saints and places where miracles or apparitions are believed to have occurred. Table 1 contains data on health risks documented at the Vatican,¹¹ Lourdes,^12–14 Shrine of Fatima,¹⁵ Santiago de Compostela,^16,17 Medjugorje,¹⁸ Church of the Holy Sepulchre,¹⁹ as well as some other pilgrimages. Christian MGs in the USA, France, Germany and Austria have been associated with several outbreaks of measles and mumps.²⁰

World Youth Day and papal visits

The Catholic Church’s World Youth Day (WYD) is a MG of young people held over ~6 days approximately every 3 years since 1984, with the Pope usually in attendance. The largest attendance reported was 5 million people in Manila, The Philippines, in 1995. The WYD event of 2008 held in Sydney, Australia, was attended by 223 000 young pilgrims from 170 different countries. Masses with Pope Benedict XVI were attended by up to 400 000 people.²¹ Influenza types A and B were identified in ill pilgrims: influenza A was most frequently isolated from Australian and German pilgrims, whereas influenza B was most frequently isolated from pilgrims from the Solomon Islands, Papua New Guinea, Australia and North America.²² The epidemiological and virological data gathered during WYD2008 highlighted the complexity of influenza outbreaks in MGs, with six distinct viruses identified among pilgrims during 1 week. Different viruses circulated in different pilgrim groups suggesting that infection was not random but influenced by country of origin and travel. The risk was not limited to MG participants, but increased influenza A and B activity was identified in all Australian states.^23,24 Papal visits to various destinations resulted in a variety of medical emergencies, some associated with the climate,^25,26 other with stress resulting in hypertension and headache.²⁷

Latin American pilgrimages

Approximately 40% of the world’s 1.37 billion Catholics live in Latin America and the Caribbean,²⁸ with the bulk residing in Brazil (145 million) and Mexico (123 million). Catholic traditions drive millions of devotees to regional and international pilgrimages where miracles are believed to have occurred.²⁹  Table 2 contains some of the known health risks.

The National Shrine of Our Lady of Aparecida in Brazil³⁰ has an on-site clinic that provides health care to ~25 000 pilgrims annually with 8% requiring a higher level of care. Non-communicable conditions, obstetric and trauma cases were the most frequent presentation, but vector-borne diseases such as dengue are of concern.^31–35 The Basilica of Our Lady of Guadalupe in Mexico City is among the most visited Catholic sites in the world. About 11 million local and international visitors gathered around the shrine during the main festivities in December of 2022.^36,41 Between 3000 and 8000 patients are seen annually. Reasons for consultation are available from similar pilgrimages in Mexico and include musculoskeletal, gastrointestinal, cardiovascular and metabolic conditions.^37,38 Thousands of pilgrims reach the Basilica walking hundreds of miles from different Mexican states and traffic accidents involving pilgrims walking on highways are commonly reported. Foreign pilgrims, including Mexican nationals coming from other countries, may experience health conditions common to other types of travellers including acute diarrhoea and dengue fever. Gastrointestinal infections are common in Mexico and food and water precautions may partially mitigate the risk. The Iztapalapa Passion Play in Mexico has been associated with the spread of the 2009 H1N1 influenza pandemic,³⁹ and the 5-day Lord of Miracle procession in Peru is a large gathering where non-communicable diseases and injuries are reported. Increased risk for dengue fever is likely given recent large outbreaks in Lima in recent years.⁴⁰

African pilgrimages: Zion Christian Church

In 2020, Independent African Churches (IACs) were estimated to have 243 million members out of a population of 1.14 billion in Sub-Saharan Africa.⁴² These terms refer to ‘A church which has been founded in Africa by Africans primarily for Africans’,⁴³ which have assimilated African traditions into their practices and beliefs.⁴⁴ Some have specific pilgrimages, such as the 3-day 80-km walk from Ebhohleni to the Holy Mountain at Nhlangakazi undertaken by members of the Shembe Church in South Africa’s KwaZulu Natal province.⁴⁵ Healing is an important component of many IACs and pilgrimages are often undertaken to complement African traditional medical practices and western medicine, a practice termed ‘medical pluralism’.⁴⁶

The Zion Christian Church (ZCC) has an estimated membership of 20 million.⁴³ Two pilgrimages take place annually to its headquarters based in Moria in the Limpopo province of South Africa; the largest occurs during the Easter weekend with pilgrim numbers estimated between 5 million⁴⁷ and 12 million.⁴⁸ Undertaking a pilgrimage is considered as part of a duty.⁴⁹ The ZCC is noted for its tightly knit structures and a paucity of information is available about health structures and outcomes.⁴⁸

Attendees are overwhelmingly from South Africa (95%) with Zimbabwe (2%), Malawi (1%), Botswana (1%) and Namibia (1%) making up the balance.⁵⁰ About 98% are repeat visitors with an average age of 30 years.⁴⁹ Travel by pilgrims to Moria is exclusively by road, and one study alluded to 99% of respondents being concerned by the traffic and travel issues.⁴⁹ In March 2024, 45 Botswana citizens died in a bus accident en-route.

Despite the large numbers, no stampedes, infectious diseases outbreaks or other health hazards have been documented since the 1910 inception of the church.⁴⁷ Pilgrims with tuberculosis seeking healing have been reported,⁴⁵ but no secondary cases. Sanitation programmes are run if cholera is reported in areas from where pilgrims come. Some pilgrims come from malaria endemic areas, but no cases of imported or odyssean cases have been reported. An on-site clinic and hospitals in the nearby town of Polokwane provide medical support as needed.

Muslim pilgrimages

Hajj

The Hajj is one of the largest annually recurring MGs in the world and has been extensively documented, including heat-related illnesses associated with it.⁵¹ During several specific holy days of Hajj (from the 8th to the 12th of the Hajj month based on the Islamic lunar calendar), pilgrims throng in periods of intense supplication localized at specific small sites (Mina, Arafat and Muzdalifa) and experience a number of public health challenges in the pursuit of spiritual redemption.

Hajj is unique in several respects. Its recurrence at the same sites annually contrasts with its ever-changing seasonal dates because of the Islamic lunar Calendar. As a result, Hajj falls 10–11 days earlier each year, introducing annual seasonal and climatic change. Environmental health risks may therefore also be fluid: sometimes Hajj coincides with influenza season, for instance, magnifying public health risks.^52,53 These risks may potentially worsen as infectious disease profiles change in the context of unchecked global warming.⁵⁴ Hajj has gone through the COVID-19 pandemic period, and to safeguard the wellbeing of the pilgrims, the Hajj authorities reduced the number of pilgrims significantly, limiting it to national pilgrims. This was in addition to enforcing strict infection control and prevention guidance and making the COVID-19 a mandatory requirement for hajj when it became available.^55–57 Hajj attendees (often known as Hajjes) are extraordinarily diverse in age, pre-existing health status, nationality and country of origin.

Hajj is also variable in terms of crowd behaviour.⁵⁸ Worshippers are both static and dynamic. Because all Hajjes travel as part of small informal groups, there remains some order in what could otherwise deteriorate into individual chaos. Furthermore, this flexibility safeguards Hajj at the most pressured points, which could otherwise become treacherous on occasion. Foremost being the Jamarat rituals. Table 3 contains some of the documented infectious,^59,60 heat illness^61–63 and trauma⁶⁴-related health risks associated with Hajj.

Umrah

Umrah is termed the minor pilgrimage performed by >10 million annually: Table 4 indicates the differences between Hajj and Umrah.⁶⁵ Compared to Hajj, there has been limited focussed research on Umrah, and most of the available studies did not split Umrah and Hajj data.

Following the large intercontinental outbreak of meningococcal A after the Hajj of 1987, there were several smaller outbreaks of meningococcal disease (mostly A) in Makkah that affected Umrah pilgrims till 1997.⁶⁶ In 1992, there was a sizeable outbreak of meningococcal disease with 102 confirmed cases and 80 suspected cases; 59% of confirmed cases were Umrah pilgrims with a case fatality rate of ~15%.⁶⁷ Meningococcal carriage rate among Umrah pilgrims has been low (between 0.5% and 1.3%)—in a 2001 study conducted among returned Singaporean Umrah pilgrims, the carriage rate was found to be significantly lower compared to Hajj pilgrims (1.3% vs 1.7%, P < 0.001).^68,69 There were reports of cases in pilgrims and contacts in May 2024 linked to unvaccinated pilgrims.⁷⁰

In 2019, a high prevalence (34.6%) of influenza-like illness was reported in a study of 616 multinational Umrah pilgrims.⁶⁸ In an Iranian study conducted in 2013–15 involving 712 Umrah and 1355 Hajj pilgrims, the proportion of influenza was significantly higher among Umrah pilgrims compared to Hajj pilgrims (27% vs 4%, P < 0.001)^71,72; however, a syndromic comparative study conducted in 2021 involving predominantly Saudi Umrah and Hajj pilgrims (500 in each group) found the rate of respiratory tract infections to be significantly lower among Umrah pilgrims (2.2% vs 4.7%, P = 0.05).⁷³ A larger study conducted in 2022 involving 3862 Egyptian pilgrims who returned from Umrah or Hajj demonstrated a lower prevalence of SARS-CoV-2 infection among Umrah pilgrims compared to Hajj pilgrims (6.7% vs 9.9%, P < 0.001), whereas no significant difference was observed in influenza prevalence (11.7% vs 9.2%, P = 0.275).⁷⁴

In 2005, compared to pre-Umrah period, a higher prevalence of intestinal parasites was reported among residents of Makkah during post-Umrah period (73.8% vs 66.3%, P = 0.02). The most common parasites were Entamoeba histolytica/Entamoeba dispar (57.9%) and Giardia lamblia (6.0%).⁷⁵ In 2014 and 2015, 232 cases of imported malaria were reported among travellers to Makkah, including Umrah pilgrims.⁷⁶

Compliance with preventive measures was often suboptimal in Umrah pilgrims: a survey conducted in 2019 among 1012 multinational pilgrims found that 24% had not received any vaccinations (including the compulsory ones), and the majority of pilgrims (83%) did wash their hands with soap and water or sanitizers, whereas another comparative survey conducted in 2019 showed Umrah pilgrims’ compliance with the frequent use of alcohol-based hand rubs to be significantly lower than that of Hajj pilgrims (36.3% vs 53.0%, P < 0.001).⁷⁷

Arbaeen

The Muslim Arbaeen pilgrimage in Iraq is one of the largest annual religious MGs in the world, commemorating the martyrdom of Imam Hussein, the grandson of Prophet Muhammad.⁷⁸ The number of pilgrims has approached 20 million in the last years, most of them local, though a significant proportion come from >40 other countries.⁷⁹

This event draws mostly Shia Muslim to the holy city of Karbala and has become a symbol of unity, devotion and resilience among its participants.⁸⁰ It is marked by long walks of >80 km, covered in ~3 days, from the cities of Najaf or Basra, and culminates in a visit to the shrine of Imam Hussain in Karbala. Almost all the necessary services like provision of food, drinks, accommodation and sometimes even health services are provided by the civil society free of charge through the ‘mawakeb’ established by local residents.

It creates profound pressure on the public health in the country with potential threats to regional and global health.⁸¹ It can facilitate the rapid transmission of communicable diseases, including respiratory infections, gastroenteritis and vaccine-preventable diseases because of the close contact between individuals, crowded living conditions and inadequate sanitation facilities. Inadequate water and lack of hygiene can increase the risk of water-borne diseases. There is currently surveillance structures in place.⁸² Exacerbation of chronic non-communicable diseases is another threat facing pilgrims in this MG considering the walking for long distances, changing food regimens and inadequate compliance to medications.⁸³

Different types of injuries are not uncommon during this MG. Road traffic accidents are on top of injuries leading to a significant annual morbidity and mortality. Other reported injuries include burns, falls, stampedes and others.^84,85 Terrorist attacks are another type of threat, though this probability has dramatically decreased over the last years.

Organizing a gathering of such magnitude comes with its share of challenges. The Iraqi government, along with religious authorities, has implemented various measures to address these challenges. Syndromic surveillance during MG is among the strategies adopted to monitor and early detect outbreaks of significant communicable diseases.^82,86 Other measures included crowd control, medical facilities and security arrangements, with the aim to safeguard participants and ensure the smooth conduct of the pilgrimage.

Grand Magal de Touba

The grand Magal de Touba (GMT) is the largest annual Muslim event in Senegal, gathering 4–6 million pilgrims in Touba.⁸⁷ It leads to a privileged encounter with a personal spiritual guide and honouring the founder of the Mouridism order. Pilgrims come from across Senegal and the surrounding countries, as well as from countries outside Africa. The rituals last 1 day; however, pilgrims usually stay for several days.

With the exception of cholera outbreaks in 1973 and in 2004–06,^88,89 most available data about diseases at the GMT have been published during the last 8 years. Medical care is provided to pilgrims free of charge for 5 days.⁹⁰ Most of the available local public medical infrastructures are involved in the medical preparation for, surveillance of and response to the event. At least 5244 healthcare workers were mobilized during the GMT in 2018. The Ministry of Health set up 176 medical service delivery points, which included hospitals, health care centres and advanced medical posts.⁹¹

During the 2015 GMT, of the 32 229 patients who consulted health services in Touba and the surrounding area during the 5-day period of free medical coverage, the most common reasons for medical consultation were gastrointestinal symptoms (14%), respiratory and ear, nose and throat symptoms (10%), fevers of unknown origin (5%) and confirmed malaria (3%).⁸⁸ In a 2016 study conducted among 20 850 patients, the most prevalent symptoms were headaches (28.2%), gastrointestinal symptoms (22.0%), fever (17.2%) and respiratory symptoms (17.1%), and 2.4% had confirmed malaria.⁹² Prospective cohort studies conducted from 2017 to 2021 showed that 55% of pilgrims reported respiratory tract symptoms and 13% gastrointestinal symptoms.^93–95 A proportion of 18% of pilgrims acquired at least one respiratory virus, notably human rhinoviruses (10%) and coronaviruses (6%). The acquisition of respiratory bacteria was high (40%) notably Haemophilus influenzae (19%) and Streptococcus pneumoniae (14%). The acquisition of gastrointestinal pathogens was lower, with enteroaggregative Escherichia coli (19%) and enteropathogenic E. coli (EPEC) (11%) the most frequent. A clear association of respiratory symptoms with acquisition of viruses and S. pneumoniae was observed.

Cross-sectional studies showed that in patients with a cough, 63% tested positive for at least one virus, including influenza viruses (33%). A high positivity rate of bacterial respiratory carriage was observed for H. influenzae (73%), S. pneumoniae (51%) and Moraxella catarrhalis (46%). In patients with diarrhoea, 71% were positive, with high rates of bacterial carriage, ranging from 4% for Tropheryma whipplei to 45% for EPEC. In patients with fever, 32% had pathogens detected, including Plasmodium falciparum (21%), Borrelia sp. (6%) and dengue virus (5%).^96,97

Bishwa Ijtema

The Bishwa Ijtema is an annual Muslim religious mass gathering in Bangladesh.^98,99 The Ijtema takes place over 3 days and is held in two phases, a week apart. In 2024, the first phase of the Ijtema was held from 2 to 4 February, and the second phase took place from 9 to 11 February. An estimated 1.7–4 million, mostly local participants, attend, with about 50 000 foreigners from 50 countries having a specific reserved area.¹⁰⁰ The event includes collective prayers and sermons, with attendees striving to sacrifice worldly luxuries.

The Ijtema has its own permanent 160-acre site in Tongi on the outskirts of Dhaka. The logistics, management of the event and accommodation of attendees are co-ordinated by a central Ijtema management structure with teams of volunteers and crucial support provided by the Bangladeshi government. A large jute canopy is erected over the 1-km-long prayer ground. The physical limitation of the main site means that people often sit on roads, by-lanes and rooftops to get a better view of the proceedings.⁹³ The government implements safety and security arrangements including observation towers for members of the rapid Action Battalion to oversee the entire event and ensure security.

Health risks (both communicable and non-communicable diseases) pose significant public health concerns, particularly for older individuals and those with pre-existing health conditions. Respiratory infections as well as exacerbation of asthma are common in cold weather conditions. Vector-borne diseases like dengue and chikungunya are a cause for concern,¹⁰¹ as is the risk of water-borne diseases such as dysentery through contaminated water sources or improper handling of food and waste. More than 2000 cases of diarrhoea were treated in 2023.¹⁰²

To avert these risks, the government provides temporary hospitals and medical centres and deploys a significant number of medical and sanitation teams located at the Ijtema grounds. Tertiary hospitals are in close proximity to ensure accessible healthcare and transfer as needed. Many private social and religious organizations play a crucial role by offering free medical treatment round the clock.¹⁰³

Hindu pilgrimage: Kumbh Mela

The Kumbh Mela celebrated in India is the largest peaceful congregation of pilgrims on Earth. It is a confluence of spiritual, cultural and historical heritage and encapsulates the science of astronomy, spirituality, ritualistic traditions and sociocultural practices, making it a culturally diverse gathering. The Magh (small) Mela is held annually only at Prayagraj. The Kumbh Mela is held approximately every 3 years by rotation in Nashik, Ujjain, Haridwar and Prayagraj. The Ardh (half) Kumbh Mela is held every 6 years either at Haridwar or Prayagraj. The Purna (full) Kumbh Mela takes place every 12 years; the 2013 event attracted >80 million pilgrims over 55 days and the 2025 event is projected to attract >150 million. The Maha (great) Kumbh Mela takes place every 144 years. Bathing in the involved rivers is the primary objective and on the main bathing days there is huge surge of pilgrims. It is believed that bathing at the Sangam can absolve all sins, liberating the person from the endless cycle of birth, death and rebirth, thereby ensuring Moksha or salvation.

Cholera has been historically associated with the Kumbh. The first Asiatic cholera pandemic of 1817–24 began with the 1817 Kumbh Mela from where it spread beyond the Indo-Gangetic delta. British naval officers and Hajj pilgrims carried the disease from central India to all parts of the subcontinent and then onwards to the Far East, Western Asia and the Mediterranean. The 6^th cholera pandemic (1899–1923), which could be traced to Haridwar, resulted in the deaths of 800 000 worldwide.¹⁰⁴ Subsequent sporadic epidemics during the Kumbh Mela in 1948 and in the 1960s lead the government to order compulsory cholera inoculation of all visitors. However, this requirement has since been relaxed.

In 2013 in Prayagraj, ~280 000 patients attended local clinics and data were captured from 49 131 of these consultations. About 5% of attendees reported diarrhoea within 48 h of bathing.¹⁰⁵ Another study of the same 2013 event documented over 400 000 consultations with 70% presenting with respiratory conditions.¹⁰⁶ In 2019 in Haridwar, among the reported illnesses, 95% were communicable diseases such as acute respiratory illness (35%), acute fever (28%) and skin infections (18%). The remaining 5% were non-communicable diseases like injuries, hypothermia and burns. Two outbreaks (acute gastroenteritis and chickenpox) were reported, investigated and controlled.¹⁰⁷ The 2021 Kumbh Mela emerged as a potential COVID-19 super-spreader event with an increase of 37 cases per day to 144 cases per day (276%) in Haridwar.¹⁰⁸ An increase from 138 to 480 cases per day (236%) and from 45 600 to 92 754 cases per day (92%) was noted in Uttarakhand and India, respectively, during the pilgrimage. A similar pattern was noted at the Magh Mela.¹⁰⁹

Gross antibiotic overuse has been documented at the 2013 and 2015 Kumbh Melas with rates of antibiotic prescribing up to 31%.¹¹⁰ Management of sewage poses a significant challenge and such wastewater provides an appropriate environment for anti-microbial resistance (AMR).^111–113 Recent emerging and re-emerging vector-borne diseases in India, including dengue, chikungunya and Nipah viruses, are of major concern and mosquito bite avoidance is of utmost importance for the 2025 event. Stampedes (500 and 38 deaths in 1954 and 2013, respectively) is another consideration. Table 5 indicates some of the larger Hindu pilgrimages.

Hindu and Buddhist pilgrims undertake journeys to Gosainkunda Lake in Nepal, which is at an altitude of 4300 m. Acute mountain sickness, high-altitude cerebral oedema and high-altitude pulmonary oedema have all been documented.^114,115 Kailash Manasarovar is another high-altitude pilgrimage destination for Hindu and Buddhist pilgrims in Tibet where mountain sickness has been documented.¹¹⁶ However, these primarily affect Hindus travelling to high-altitude destinations. Stampedes have been documented at a number of festivals,¹¹⁷ with a recent one in early July 2024 resulting in the death of at least 120 attendees.¹¹⁸

Some other pilgrimages

Buddhist pilgrimages

Pilgrimage, from a Buddhist point of view, is a way of gaining merit by focussing one’s energies on visiting sacred sites, such as the four main places associated with the Buddha’s life: his birthplace in Nepal, and the places in India where he gained enlightenment, gave his first teachings and where he died. The Great Stupa in Boudhanath, Nepal, is another important pilgrimage destination, where hundreds of people per day circumambulate to gain merit. In addition, there are many places where great masters practised that are said to contain great blessings, or sacred mountains and lakes to visit and circumambulate. In this context, pilgrimage is a personal journey, although in popular destinations, they may encounter many other pilgrims along the way.

Mass gatherings, in the Tibetan Buddhist tradition, usually involve receiving ritual empowerments and teachings, such as the Kalachakra empowerment given by His Holiness the Dalai Lama, at which hundreds of thousands of pilgrims might attend for several days. But these are infrequent events, not regularly scheduled.¹¹⁹ The Wesak (or Wesak) Festival or popularly known as Buddha Day,¹²⁰ is one such event with the 2023 festival celebrated in Vietnam over 2 days, with representation of 13 countries and >70 000 Buddhists.

Jewish pilgrimages

The annual Lag BaOmer pilgrimage to Mount Meron in Israel falls on the 33rd day of the Omer: 49 days between the end of Passover and Shavuot. The annual gathering, which takes place at what is believed to be the gravesite of the second-century Talmudic sage Rabbi Shimon Bar Yochai, is the largest Jewish pilgrimage in modern times,¹²¹ with an estimated 250 000 persons attending overall and 100 000 present on-site during the peak hours.¹²²

The pilgrimage typically involves singing, dancing and lighting bonfires as a symbol of the spiritual light attributed to Rabbi Shimon. It is a joyous occasion marked by unity, prayer and celebration of Jewish heritage and tradition. The large crowd at the tomb of the rabbi pose risks of stampedes, overcrowding and accidents. In 2021, a stampede led to 45 deaths and 150 injuries. Bonfires pose a potential risk of fires spreading to other areas, as well as an increased risk of burns. Furthermore, smoke inhalation may increase the risk of bronchitis and worsening of asthma.¹²³ Weather-related incidents, depending on the season, infectious disease risks due to the crowds and mental health issues have also been considered.

Summary

For most religious MGs, accurate evidence-based data on the burden of communicable and non-communicable diseases, heat-related illnesses and mental disorders are limited.^124,125 These are required for needs assessment for both public health services, prioritizing health needs of pilgrims, and developing optimal pre-travel, during pilgrimage and post-pilgrimage prevention, management, surveillance and control guidelines. Implementing a system of real-time monitoring of diseases and morbidity patterns, utilizing modern information-sharing platforms including AI for rapid detection, management and decision making and to update WHO event-based planning and prevention guidelines for all future mass gathering events, should be the ideal.^126,127 AI can be used by clinicians and travellers pre-travel to fine-tune the intended journey, and augmented reality may be used to warn a pilgrim in real time via a smart device of a potential danger, such as a stampede possibility during Hajj.¹²⁸ Countries hosting mass gathering religious events need to collaborate more effectively and collect high-quality data and share their experiences. The COVID-19 pandemic affected all countries that host religious pilgrimages, and many were either scaled down or cancelled.

Mass gathering religious events pose a major threat to global health security via importation, transmission and exportation of a range of infectious diseases threats.¹²⁹ The threat of yet another pandemic from a coronavirus remains likely because coronaviruses exhibit great genetic diversity and high rates of adaptive mutations, and readily cross species. Numerous questions regarding the epidemiology, transmission, pathogenesis, early diagnosis and management of a range of infectious diseases, including AMR, which occur at religious mass gatherings, remain unanswered.¹³⁰ Some tools, such as for surveillance for AMR, have been developed.¹³¹ There remains an urgent need, and huge opportunities, to take forward a unified collective approach for research collaborations across all MG religious events. Proactive surveillance for viral and bacterial infections needs to be intensified and proactive testing will remain a priority for all future religious MG events.

Author Contributions

Salim Parker (conceptualization, introduction, manuscript preparation, African Christian pilgrimages, editing), Robert Steffen (conceptualization, manuscript preparation, European Christian pilgrimages, editing), Harunor Rashid (conceptualization, Umrah, editing), Miguel M Cabada (South American pilgrimages, editing), Ziad A. Memish (conceptualization, Hajj, editing), Philippe Gautret (European Christian pilgrimages, Grand Magal de Touba, editing), Cheikh Sokhna (Grand Magal de Touba, editing), Avinash Sharma (Kumbh Mela, Hindu pilgrimages, editing), David R. Shlim (Buddhist pilgrimages), Eyal Leshim (Jewish pilgrimages), Dominic E. Dwyer (World Youth Day, editing), Faris Lami (Arbaeen), Santanu Chatterjee (Kumbh Mela, Hindu pilgrimages, editing), Shuja Shafi (Bishwa Ijtema, conceptualization, Hindu pilgrimages, Arbaeen, editing), Alimuddin Zumla (conceptualization, Arbaeen, summary, editing), and Ozayr Mahomed (conceptualization, manuscript preparation, introduction, Buddhist and Jewish pilgrimages, editing)

Conflict of interest

None declared.

Author Statements

The manuscript has been seen and approved by all authors, who accept full responsibility for the content. All authors had full access to the data and their analysis, and to the drafting the article as well as editing circulating drafts.

Funding

No financial assistance was received for this manuscript.

References