The availability of a first hepatitis A vaccine in 1992 raised the possibility of its use for workers exposed to sewage or sludge. This occupational risk was suspected because of the excretion of hepatitis A virus (HAV) in stools and its resulting presence in sewage, because of the resistance of HAV to environmental stresses, and because of the documented wastewater-mediated transmission of HAV in the general population. On the other hand, the decreased diffusion of HAV in industrialized countries probably results in less contamination of sewage. The aim of this study was to evaluate the possible risk of HAV infection from sewage exposure, which could lead to recommendations of vaccination for exposed workers.
In a large private company involved in water supply, anti HAV IgG were sought in sera from workers in contact with sewage and from workers not exposed to sewage. Subjects were individually matched for age and education level. Cases included workers involved with the wastewater collection network, workers who monitor drinking water distribution networks in Paris (located in sewer mains in Paris), personnel of a large research laboratory involved with wastewater and sludge, as well as a few workers involved with drinking water production who may be frequently exposed to raw Seine river, Marne river or Oise river water (that could be contaminated with sewage). Histories of jaundice, travels to areas of endemic incidence of hepatitis A, and the duration of occupational exposure were noted. Anti-HAV IgG was measured in serum by an enzyme-linked immunosorbent assay (ELISA) method.
At this time, 110 exposed workers and 110 non-exposed workers have been studied. Ages ranged from 20 to 58 years, with a mean value of 36.5 year. Cases and controls did not differ with respect to social class or travels in areas of endemic exposure. Duration of exposure ranged from 1 year to 36 years, with a mean value of 10.3, and was correlated to age in this company where workers are usually hired when young. The seroprevalence of anti HAV was globally 52.7 %, significantly higher in exposed workers ( 60.9 %) than in controls ( 44.5 % , p < 0.02 ). This seroprevalence varied widely according to age: for workers in their twenties it was 30.0 % vs. 27.5 %, in their thirties 68.0 % vs. 33.3%, in their forties 80.0 % vs. 54.8% and in their fifties 93.3 % vs. 86.7 %, respectively in exposed and non-exposed workers. The seroprevalence was related to education level in each group, but not to social class. History of jaundice was not correlated with anti HAV status, nor with sewage exposure. The relative risk of HAV infection in this matched range was 2.4, CI 95 % (1.6 - 3.1).
These results emphasize the role of occupational exposure to sewage in HAV infection. Exposed workers should be vaccinated because of the frequency of the symptomatic form of hepatitis A in adults with severe and relapsing cases. The strategy of vaccination should take into account the high cost of the vaccine and the epidemiological situation of HAV in the country.
Hepatitis A virus, wastewater, exposed workers, vaccination.
O Schlosser, Compagnie Générale des Eaux, Service Médical, 52 rue d'Anjou, 75384 Paris Cedex 08, FRANCE