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Hajj pilgrims may contribute to transmission of influenza
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Pilgrims traveling to the annual hajj in Saudi Arabia may be at increased risk for contracting and transmitting influenza, according to a letter to the editor published in Emerging Infectious Diseases.
The authors of the letter also suggested that hajj pilgrims may not be at increased risk for Middle East respiratory syndrome, or MERS, coronavirus, as was commonly believed.
The letter described a prospective cohort study evaluating 129 adult hajj pilgrims who traveled from southern France to Saudi Arabia from Oct. 3 to Oct. 24, 2013. Before departure, all pilgrims were given advice about personal prevention efforts against respiratory tract infection, with follow-up continuing throughout the trip by a medical doctor who also tracked travel-associated diseases. The researchers collected nasal swab specimens before the return trip from Saudi Arabia to France, and each sample was tested for MERS, influenza A and B viruses and influenza A(H1N1)pdm09 virus.The samples were assayed by real-time reverse transcription PCR. The mean age of the pilgrims was 61.7 years (range 34-85 years). Forty-six (35.7%) pilgrims said they had been vaccinated against influenza in 2012. None of them had yet received the vaccine in 2013 due to its lack of availability in France at that time.
The researchers found that 90.7% of the travelers had respiratory symptoms while in Saudi Arabia, including cough (86.8%) and sore throat (82.9%). Nearly half reported fever, and 47.3% had collections of symptoms that could qualify as influenza-like illness. One patient was admitted to a hospital during the trip for undocumented pneumonia. When nasal swab samples were collected 1 day before departure from Saudi Arabia, 69.8% of the pilgrims continued to have symptoms.
All PCR results were negative for MERS, but eight of the pilgrims tested positive for influenza A(H3N2), one for influenza A(H1N1)pdm09 and one for influenza B virus.
At 3 to 5 weeks follow-up after returning home, 78.6% of pilgrims reported continued respiratory symptoms. The 10 pilgrims who had tested positive for influenza had been cleared of the infection.
The authors said the percentage of infected individuals may have been underestimated, since the samples were taken at the end of the trip, when some of the infections may have cleared.
“Our preliminary results indicate that pilgrims from France returning from the 2013 hajj were free of MERS-[coronavirus], but that a proportion were infected with influenza viruses and may represent a potential for early introduction of influenza in southern France …” they wrote. “Influenza vaccination should be a priority for pilgrims attending the hajj.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Donald Kaye, MD
Not surprisingly, this study showed no acquisition of MERS in a group of 129 pilgrims. There have only been about 145 cases in Saudi Arabia, a country with a population of 28 million. Even if MERS were easily transmissible, which it obviously is not, the chances of exposure to or acquisition of infection in this relatively small group would be diminishingly small. Furthermore, this is a group that had been counseled about individual prevention measures against respiratory tract infection.
What is astonishing to me is the extraordinary amount of respiratory disease, with more than 90% reporting symptoms (>80% reporting cough and/or sore throat and almost 50% reporting fever). It is hard to believe that such a high percent developed clinical infection. Even within the same family, the occurrence of clinical influenza is much lower. The fever was apparently subjective, which with ambient temperatures in the 90s, is difficult to assess. The amount of respiratory illness was undoubtedly increased because of the crowding, but the question is how much of an increase? Without any kind of control group with similar “close surveillance,” these data are difficult to interpret.
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