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ABSTRACT |
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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INTRODUCTION |
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To find out the extent, if any, to which contact with CCHF patients can cause hospital staff to test positive for anti-CCHF antibody, we studied the seroprevalence among those HCWs who had come in contact with CCHF patients in three referral hospitals in Systan-Baluchestan and Isfahan, the two provinces of Iran with the highest confirmed cases of CCHF in the 2001 outbreak.11
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MATERIALS AND METHODS |
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After short (30-minute) briefing sessions, 77.90% (268/344) of the workers, 81.07% (167/206) from wards deemed exposed and 87.68% (121/138) from unexposed wards, completed the screening questionnaire that also asked the staff to indicate their willingness to participate in the study.
A pre-tested self-administered questionnaire was used for data collection. The participants completed the questionnaire anonymously, and confidentiality was maintained. The questionnaire asked for information on age, sex, residential area, job, and educational level. The exposed staff described their routes of contact with CCHF patients by selecting one or more of the five proposed routes of exposure: (1) contact between injured skin and blood or other body fluids (the percutaneous route); (2) direct contact (without gloves) between intact skin and blood; (3) direct contact between intact skin and nonsanguineous body fluids; (4) direct skin-to-skin contact; and (5) exposure or respiratory contact, defined as closeness to CCHF patient(s) without any actual contact while not wearing a mask. The co-workers of the study helped the respondents in completing the questionnaire by explaining and answering questions as required.
Blood samples (10 mL each) were collected from the enrolled subjects, immediately centrifuged in the local laboratory, and transmitted in ice bags within 6 hours to the arbo-virus and hemorrhagic fevers’ laboratory of the Pasteur Institute of Iran, the reference laboratory in Tehran. Sera were checked by ELISA method for CCHF virus-specific IgG antibodies.12 Samples that revealed positive results were rechecked and were also tested for the virus-specific IgM to exclude acute infection.
Data were analyzed with SPSS 13.0 for Windows (SPSS Inc., Chicago, IL) and Stata Statistical Software, version 8.0 (StataCorp LP, Geneva, Switzerland). For each point prevalence, 95% confidence intervals (CI) were calculated. Fisher’s exact and 
2 (for qualitative variables) as well as Wilcoxon-Mann-Whitney (for quantitative variables) tests were used to compare the characteristics of the study groups. For multivariate analysis, logistic regression was performed with enter method including study group, residential province, sex, age, educational level, and job variables. Confidence intervals for odds ratios, Wald test statistic (testing the null hypothesis that the relative risk of seropositivity associated with the predictor variable is unity) and associated P values with one degree of freedom were calculated. The goodness-of-fit of the model was shown by the 2 log likelihood (–2LL), the Nagelkerke R2, and was tested by Hosmer-Lemeshow test. Statistical significance was set at P < 0.05.
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RESULTS |
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In the exposed group, 5 of 129 (3.87%, 95% CI: 0.55–7.20, Table 1
) tested positive for anti-CCHF IgG; in the unexposed group, none tested positive (Fisher’s exact test P = 0.075). All IgG-positive cases were from Systan-Baluchestan province and all were IgM negative (Table 2). In univariate analysis, age was the only variable that showed a significant difference between the IgG positive and negative subgroups within the exposed group (Table 1). Similarly, only the older subjects showed significant relation with seropositivity in multivariate analysis (odds ratio = 1.32; 95% CI: 1.03–1.69). Despite insignificant Wald test P value, the regression coefficients for both study group (3E + 8) and residential province (2E + 8) were found to be very large. The 2 log likelihood (–2LL) of 23.30, Nagelkerke R2 of 0.54, and insignificant Hosmer-Lemeshow test (2 = 0.91, P = 0.99) indicated that the model used for multivariate analysis did fit the data.
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DISCUSSION |
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The rate of IgG seropositivity found in this study was higher than that found in other rare reports of seroprevalence among staff with a history of contact with CCHF patients.5,9,10 This variation might be due to the differences in study powers, in the degree to which the staff observed the mandatory precautions, and in the amount of potentially harmful contacts.
The limited number of seropositive cases compared with seronegative ones in exposed group (5 versus 124) precludes any statistical correlation between seropositivity and any of the five routes of potentially harmful contact. Although percutaneous exposure is believed to impose the highest risk of transmission,6,7,17 evidence regarding other routes is controversial. Although airborne transmission has not been documented in humans,5,17,18 some reports of infection with other viral hemorrhagic fever viruses like Ebola virus in animals through this route19,20 as well as infection without any documented direct exposure to infectious material21 make it impossible to rule out the risk from any mode of exposure. Our finding one seropositive orderly who had a history only of respiratory contact, despite the recall bias, also supports this conclusion and suggests that HCWs should observe all safety measures including barrier nursing and isolation as well as using face shields or surgical masks, eye protection, and gloves as appropriate when handling infected patients, their blood and other body fluids, or even when simply working in proximity to CCHF patients.
Our study has a few serious limitations. Firstly, recall could bias the recruitment of exposed and unexposed groups although hospital records were also used to determine the history of contacts. Furthermore, we limited the history of exposure to CCHF patients to 2 years before the study as one of our inclusion criterion. Secondly, although each type of exposure was fully defined and described both in the questionnaire and during the briefing sessions, the same recall bias together with failure to recognize the contact route, especially by inadequately qualified staff, could affect the validity of the history of prior contact. Thirdly, the rarity of seropositive cases, over which the authors had no control, together with the relative multitude of the routes for hospital staff to come in contact with patients made it difficult to assess the risk associated with each specific route.
In conclusion, we found that HCWs in contact with CCHF patients, those who live in Systan-Baluchestan province, and those who are older are more likely to test positive for anti-CCHF IgG. All the HCWs, and particularly those in the three high-risk categories mentioned earlier, should take all protective measures whenever they are likely to come in contact with CCHF patients or with their blood and other body fluids unless further studies exclude any of the possible routes of contact.
Received July 25, 2006. Accepted for publication December 7, 2006.
Acknowledgments: This study was partially supported by a grant from the Faculty of Medicine, Shaheed Beheshti University of Medical Sciences, Tehran, Iran. The American Society of Tropical Medicine and Hygiene (ASTMH) assisted with publication expenses.
* Address correspondence to Mohammad Rahnavardi, Infectious Disease and Tropical Medicine Research Center, Shaheed Beheshti University of Medical Sciences, Velenjak, Chamran Highway, Tehran, Iran. E-mail: rahnavardi{at}gmail.com 
Authors’ addresses: M. Mardani, M. Rahnavardi, and M. Rajaeinejad, M. Rostami, and M. Hashemi Shahri, Infectious Disease and Tropical Medicine Research Center, Shaheed Beheshti University of Medical Sciences, Velenjak, Chamran Highway Tehran, Iran, Telephone: +98-21-2242-4206 and +98-21-2242-4205, Fax: +98-21-8895-1402. K. Holakoui Naini, F. Pourmalek, Department of Epidemiology and Biostatistics, School of Public Health and Institute of Health Research, Tehran University of Medical Sciences, Poursina St., Keshavarz Blvd., Tehran, Iran. Telephone & Fax: +98-21-889-51-402. S. Chinikar, Pasteur Institute of Iran, Pasteur Ave., Tehran, Iran. Telephone: +98-21-6640-4007, Fax: +98-21-6646-5132.
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REFERENCES |
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This article has been cited by other articles:
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  M. Mardani, M. Keshtkar-Jahromi, B. Ataie, and P. Adibi Crimean-Congo Hemorrhagic Fever Virus as a Nosocomial Pathogen in Iran Am J Trop Med Hyg, October 1, 2009; 81(4): 675 - 678. [Abstract] [Full Text] [PDF]
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