Intended for healthcare professionals

Rapid response to:


Climate related migration and displacement

BMJ 2022; 379 doi: (Published 12 October 2022) Cite this as: BMJ 2022;379:o2389

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Rapid Response:

The Ischia flood and its potential effects on human and animal health

Dear Editor,

The dramatic flood which on November 26 hit Ischia, following a similar event which 13 years before had already affected this beautiful island facing the city of Naples, is a further reminder of the Italian territory's fragility and hydrogeological instability. The latter is known to result, in turn, from rampant urbanization and illegal building, coupled with the climate change-driven extreme weather events characterizing the current Anthropocene epoch.

Among the flood-related/associated effects, the transfer of infectious pathogens from terrestrial into marine ecosystems is a matter of concern (1,2), with special emphasis on bacteria transmitted via the faecal-oral route like Salmonella spp., Escherichia coli, Vibrio cholerae and Listeria monocytogenes, or protozoa like Toxoplasma gondii, or viruses like the one causing hepatitis A and, last but not least, SARS-CoV-2, the betacoronavirus responsible for the devastating CoViD-19 pandemic. Indeed, faecal viral shedding has been reported for a median duration of 22 days in 59% of subjects from a cohort of SARS-CoV-2-infected patients in China (3).

Once conveyed into sea water by flood-derived mud and debris, faecally transmitted pathogens may be ingested by edible bivalve molluscs like mussels, which can filter up to 100 liters of water every day, thereby potentially hosting inside their body tissues significant amounts of biological and chemical environmental contaminants (4). Noteworthy, a Vibrio cholerae infection outbreak, originating from the consumption of raw, non-sterilized mussels, diffusely involved the human population from the cities of Naples and Bari during the summer and early autumn months of 1973 (5).The infectious agents' land-to-sea transfer may additionally affect wild cetaceans, whose health and conservations status appears to be increasingly threatened by human activities. This especially concerns "inshore" or coastal species like bottlenose dolphins (Tursiops truncatus), which then become more prone to acquire infections caused by "terrestrial" pathogens like T. gondii (6). Furthermore, based upon the significant homology degree of their angiotensin-converting enzyme-2 (ACE-2) viral receptor with the human one, bottlenose dolphins as well as other marine mammal species inhabiting Mediterranean Sea waters have been deemed potentially susceptible to SARS-CoV-2 infection (7), which has not been hitherto described, however, in any cetacean species.

In conclusion, let me finally underscore the urgent need to cope with the aforementioned hydrogeological instability-related/associated health issues via a holistic, multidisciplinary, evidence- and One Health-based approach, which reminds us that human, animal and environmental health are reciprocally and tightly linked to each other!


1) Martinez-Urtaza J., et al. (2004). Influence of environmental factors and human activity on the presence of Salmonella serovars in a marine environment. Appl. Environ. Microbiol. 70:2089-2097.
2) Funari E., Manganelli M., Sinisi L. (2012). Impact of climate change on waterborne diseases. Ann. Ist. Super. Sanita 48:473-487.
3) Zheng S., et al. (2020). Viral load dynamics and disease severity in patients infected with SARS-CoV-2 in Zhejiang province, China, January-March 2020: retrospective cohort study. BMJ 369:m1443. doi:10.1136/bmj.m1443.
4) Morricone A., Pedicino V. (1986). Dizionario Dietetico degli Alimenti, Garzanti Editore, Milan, Italy, p. 533.
5) Lomonaco T. (1974). Il colera in Italia [Cholera in Italy]. Minerva Med. 65:1575-1578.
6) Di Guardo G., Mazzariol S. (2013). Toxoplasma gondii: clues from stranded dolphins. Vet. Pathol. 50:737. doi:10.1177/0300985813486816.
7) Audino T., et al. (2021). SARS-CoV-2, a threat to marine mammals? A study from Italian seawaters. Animals (Basel) 11(6):1663. doi: 10.3390/ani11061663. 

Competing interests: No competing interests

29 November 2022
Giovanni Di Guardo
Retired Professor of General Pathology and Veterinary Pathophysiology at the Veterinary Medical Faculty of the University of Teramo, Località Piano d'Accio, 64100 Teramo, Italy
Private address: Viale Pasteur, 77 - 00144 - EUR - Rome, Italy