When this news story reached the NoroCORE office, we did a double take. Hepatitis E on a cruise ship? Really?
Recently, passengers on two consecutive Golden Princess cruises sailing out of Melbourne, Australia were notified to watch for symptoms of hepatitis E virus (HEV), after a crew member on board had been diagnosed with the disease. The warning applied to passengers who sailed between February 8th and 15th, and the perceived risk of infection in this case was believed to be low.
What is hepatitis E virus?
Hepatitis E virus was identified in the 1980’s almost by accident, when samples from a waterborne hepatitis outbreak in India came back negative for the usual hepatitis A or B viruses (Wong et al., 1980). It was in fact a different virus altogether, and is now the sole member of its own genus and family.
Hepatitis E virus is a pretty rare cause of foodborne illness, and in developed countries it is most often connected with consuming undercooked pork. The symptoms are similar to hepatitis A virus, such as vomiting, fever, and abdominal pain, which are generally mild and are not lasting. It can likewise take a few weeks for symptoms to develop, and there are parts of the world where HEV is endemic, or regularly found. For this reason, people also sometimes acquire the virus while traveling, such as by drinking contaminated water.
Interestingly, even though hepatitis E cases are uncommon in the United States and several other parts of the world, one study suggests that about one in five Americans has antibodies to the virus (meaning their bodies have been exposed to the virus at some point) (Kuniholm et al., 2009) and swine appear to be a natural reservoir for HEV (Meng et al., 1997).
The disease is also rare in Australia, and according to one report, there are only 10-30 HEV cases reported to the Australian government each year.
Is this story unique?
There appears to have been only one other instance of hepatitis E affecting passengers on a cruise ship, back in 2008 (Said et al., 2009). The cruise lasted over two months, traveling around the world, taking on and letting off passengers as it went. At its end, four of the passengers returning to the United Kingdom had acute cases of hepatitis E infection. In addition, epidemiologists tested the blood of 789 of the people on board, and found that a quarter of them had antibodies to HEV.
Looking back as far as 1994, there hasn’t been an outbreak of viral hepatitis (A or E) investigated by the CDC’s Vessel Sanitation Program. An important caveat though is that unlike norovirus and several of the bacterial causes of gastroenteritis, hepatitis A and E both have long incubation periods of weeks to months, longer than most cruises, and again, the virus is rarely encountered on ships.
In short, we will be surprised if we hear of another HEV concern on a cruise ship in the next decade :-).
Kuniholm, M. H., Purcell, R. H., McQuillan, G. M., et al. 2009. Epidemiology of hepatitis E virus in the United States: Results from the third national health and nutrition examination survey, 1988–1994. J Infect Dis, 200: 48–56. Link.
Meng, X. J., Purcell, R. H., Halbur, P. G., et al. 1997. A novel virus in swine is closely related to the human hepatitis E virus. Proc Natl Acad Sci, 94: 9860–5. Link.
Said, B., Ijaz, S., Kafatos, G., Booth, L., Thomas, H., Walsh, A. et al. 2009. Hepatitis E Outbreak on Cruise Ship. Emerging Infectious Diseases, 15(11), 1738-44. Link.
Wong, D. C., Purcell, R. H., Sreenivasan, M. A., Prasad, S. R., Pavri, K. M. 1980. Epidemic and endemic hepatitis in India: evidence for a non-A, non-B hepatitis virus aetiology. Lancet, 2: 876–9.