Serotypes of influenza during Hajj season, 1424 (2004)

Each year around 1.2 million Muslims from all over the world assemble for at least two weeks in Makkah to perform Hajj, the fifth pillars of Islam. They are joined by about 0.7 million hajjis from Saudi Arabia and 0.3 million local residents of Makkah. In such crowded situations potential for transmission of respiratory infections like influenza is quite high. But as the information about its serotypes circulating in Hajj is lacking, no evidence based recommendations can be made for the contents of influenza vaccine to be used in Hajj.

A cross sectional study was conducted to identify circulating serotypes of influenza virus and collect other baseline epidemiological information to help in development of routine influenza surveillance system in Saudi Arabia.

The study was conducted at both Makkah and Mina health care facilities during Hajj season 1424 H. Health care facilities were selected on the basis of the high number of Acute Respiratory Tract infection cases presenting there during previous hajj season, and also proximity to the Haram in case of Makkah health facilities. In Makkah, it included three hospitals: Ajyad Hospital, King Abdul Aziz Hospital and King Faisal Hospital; and in Mina it included Mina General Hospital, Mina Al-Wadi Hospital and Primary Health Care center number 13.

For the purpose of this study a suspected case of influenza was defined as any patient, aged one year or above, presenting with fever of at least 38°C, started within 72 hours of presentation; along with history of cough and/or sore throat.

During the study period 56 to 14th Dhul Hijja, 1424 H (27/01/2004 to 05/02/2004), all patients fulfilling the criteria of case definition of suspected influenza at the participating health facilities were identified in screening clinics established at OPD and ER of participating facilities and invited to participate in the study, irrespective of their nationality, residential or hajj status. All participants were interviewed using a structured questionnaire and a throat swab was taken for viral isolation. The swabs were later analyzed at King Abdul Aziz University virology laboratory in Jeddah.

A total of 415 suspected influenza €¢cases were identified and interviewed in participating health facilities during the study period, among whom 44.6% were recruited from Ajyad hospital.

The ages of the suspected cases ranged between 1-86 years (mean 39.3, SD ± 15.65). The majority of participating suspected cases were Hajjis 360 (86.7%); and 135 (32.5%) suspected cases were domestic i.e. residents of Saudi Arabia whether Saudi nationals or not (Table 1). The suspected cases belonged to 36 different nationalities. Only 26.4% had been in the hajj area for 3 days or less (maximum usual incubation period of influenza) before onset of illness, while 73.6% had been staying in the hajj area for more than 3 days.

The clinical features reported by the suspected cases were fever (100%), sore throat (80.2%), cough (79.5%), headache (77.1%), runny nose (58.1%), myalgia (56.4%), expectoration (26.3%) and blocked nose (21.1%). Only 2.2% of the suspected influenza cases were vaccinated against influenza and 16.1% had used antibiotics before being recruited in the study.

Among suspected influenza cases, 55 cases (13.3%) were confirmed by the laboratory by isolation of the Influenza virus: 27.3% had influenza type A viruses, and 72.7% had influenza type B viruses. The most predominant serotype among the confirmed influenza isolates was Flu B Sichuan which accounted for 70.9%, followed by Flu A not typed (14.6%), Flu A HINT (7.3%), Flu A H3N2 (5.5%) and Flu B Hong Kong (1.8%). Influenza B Sichuan serotype was the predominant strain from all the countries, except Ethiopia and Djibouti where all the three isolates were Influenza A not typed.

The ages of the confirmed cases ranged from 1-70 years (mean 37.13, SD ± 14.96). Among them, 46 cases (83.6%) were Hajjis, while 18 cases (32.7%) were domestic (Table 1). Clinical features of confirmed influenza cases were fever (100%), cough (85.5%), headache (81.8%), sore throat (76.4%), myalgia (67.3%), runny nose (58.2%), expectoration (25.5%) and blocked nose (16.4%). In none of the 8 suspected influenza cases who were vaccinated against influenza was the virus isolated. Among confirmed cases, 16.4% had used antibiotics, 78.2% had not, and 5.4% did not know.

Influenza is an acute, usually self-limiting, febrile, contagious respiratory illness caused by influenza viruses. The attack rates during outbreaks may be as high as 10-40% over a 5 to 6 week period. Influenza continues to be an important cause of morbidity and mortality in hospitalized and long-term care patients, particularly among the elderly and those with chronic underlying cardiac and pulmonary diseases.[1] It spreads very quickly among the population especially in crowded circumstances. Influenza A and B are the two types of influenza viruses that cause epidemic human disease. Influenza A viruses are further categorized into subtypes on the basis of two surface antigens: hemagglutinin (H) and neuraminidase (N). Since 1977, influenza A (H1N1) viruses, influenza A (H3N2) viruses, and influenza B viruses have been in global circulation. In 2001, influenza A (HIN2) viruses probably emerged after genetic reassortment between human A (H3N2) and A (H1N1) viruses began circulating widely.[2]

Influenza activity in Saudi Arabia begins in September and peaks in November, which may contribute to the occurrence of influenza during coming Hajj seasons and at the same time help in having a higher yield in throat swabs.[3] The type of influenza virus in circulation during hajj is important with its potential for outbreak in such crowded conditions. However, except for the study conducted by Kholeidi et al in 1421 H hajj season, no information was available about the influenza viral etiology during the hajj, and even in that study viral typing was done on the basis of serological examination of patient's blood.[4]

This study found five serotypes of influenza viruses, the most predominant type being Flu B Sichuan, which are the most common serotypes in Asian countries according to CDC and WHO reports, from where most of these patients arrived. [2,5]

Although in this type of study, where information about the denominators is not distinctly available, it is difficult to comment about the etiological relationship of disease pattern with the exposure factors; however, absence of any confirmed cases among known vaccinated patients indicate the protective effect of the vaccine. The assumption is quite reasonable as the serotypes identified in this study are already part of vaccine used in 20042005 influenza vaccine.[2]

This study indicates the need of establishment of a National program on influenza surveillance and control in the Kingdom, with special emphasis on Hajj. Its findings also recommend €¢ the encouragement of pilgrims to take influenza vaccine especially among the elderly.