Food- and water-borne diseases are caused by one of many organisms, including bacteria, viruses or parasites. Contaminated food and water can transmit a wide variety of infectious diseases, with all of these having a higher incidence in low-income counties. They are consistently spread via the faecal-oral route (TravelHealthPro, 2019a). Due to there being so many varying diseases spread in this manner, there are also an array of symptoms, ranging from very mild to severe. Some may need hospitalisation and can be fatal. Food- and water-borne diseases are still the most common health issue experienced by travellers, most commonly causing diarrhoea. Becoming unwell while travelling can cause severe disruption and ruin any holiday (Fit for travel, 2022a). This article will examine vaccine-preventable food- and water-borne diseases; therefore, traveller's diarrhoea and other water-borne diseases without a vaccine will not be covered. Health professionals need to understand when vaccines should be recommended and administered to give protection from these specific diseases. However, food and water hygiene advice should be given to all travellers to reduce the risk of contracting all pathogens caught in this manner. The vaccine-preventable diseases are poliomyelitis, hepatitis A, typhoid and cholera.
Poliomyelitis
Poliomyelitis (Polio) is a viral infection that is potentially paralysing and mostly affects the under 5's. This disease is spread via the faecal-oral route and humans are the only natural known host (TravelHealthPro, 2021a). In 1988 there were still 125 counties where polio commonly occurred, and these were spread across 5 different continents. This resulted in more than 1000 children a day becoming paralysed (TravelHealthPro, 2022a). After a global eradication initiative, there remain only two countries with endemic wild polio: Afghanistan and Pakistan. Africa declared itself wild polio free in 2020 (World Health Organization (WHO), 2020). However, since then there have been 4 cases of wild polio in Mozambique, the last being in August 2022, and 1 in Malawi in 2021, causing great concern in this region (WHO, 2023). There are 3 serotypes of human polio virus: 1, 2 and 3. When the original oral polio vaccine (OPV) was developed in the 1960s, it was a live attenuated vaccine with a mixture of all three types. The intention was that those who received the vaccine would shed the weakened virus in their stool, spreading immunity in the local population (TravelHealthPro, 2021a). Over time, but rarely, this OPV virus has mutated and is now a strain capable of causing an outbreak of paralytic polio. These viruses are referred to as circulating vaccine-derived polioviruses (cVDPV). Recent oral vaccines only include type 1 and 3 poliovirus due the emergence and outbreaks of 2 cVDPV (TravelHealthPro, 2021a).
Since 2014, polio has been a Public Health Emergency of International Concern (PHEIC) due to an unexpected increase in exportation of polio from infected countries. Due to this, the WHO made certain recommendations to try to combat the spread of the infection. The global situation is being constantly monitored and reviewed. Their last meeting was in February 2023 and there remains ongoing concerns and vaccine-derived cases in many Southern African nations, Yemen and Indonesia (WHO, 2023). Therefore, travel health consultants need to check the polio requirements individually for each country. Some travellers will now require a certification of vaccine. This may be requested on departure if they are in the country for over 4 weeks and the vaccination may need to have been given in the previous 12 months (TravelHealthPro, 2021a). Travel health consultants need to ensure that they are also aware of how to complete the certification of vaccine (TravelHealthPro, 2021b). In 2022, circulating vaccine-derived polio virus 2 was detected in London sewage samples as well as in New York State. Last year, the UK Government was offering extra booster vaccines to some groups in London, but the overall risk to UK citizens was seen as low (TravelHealthPro, 2022b). In 2023 this campaign was discontinued but it continues to be monitored.
The disease itself has an incubation period of 3–21 days, with 90% of cases being asymptomatic. Less than 1% end up with the most severe form of paralytic polio. Only supportive treatment is available for those with the disease (TravelHealthPro, 2021a). The vaccine would usually only be recommended if the patient had an incomplete polio vaccine history or was travelling to countries with a requirement or an active outbreak. Polio is almost always given as an intramuscular injection (in the UK) and as a component of a combination vaccine. There are paediatric vaccinations given from birth, and usually Revaxis is given in those over 10 years old, covering polio, tetanus and diphtheria (TravelHealthPro, 2021a). Most UK citizens will have had all their childhood vaccines and a specific booster would only be needed every 10 years in certain circumstances, but now may be required within the year for travel certificate purposes.
Hepatitis A
Hepatitis A, also known as hep A or HAV, is an infection of the liver caused by the hepatitis A virus. Even though hepatitis A has been known to the medical profession for centuries, it is only in recent years that science has begun to unravel the origins of this disease and examine the unique pathobiology underlying acute hepatitis A in humans. Due to deliberate human transmission studies in the early part of the 19th Century, its infectious nature was proven and this led to the clear distinction between hepatitis A (‘infectious hepatitis’) and other forms of hepatitis. The hep A virus was finally identified by immune electron microscopy in the 1970s (Lemon et al, 2017), leading to the production of a highly efficacious vaccine. However, hepatitis A persists in vulnerable populations and remains the most common travel-related vaccine-preventable disease (TravelHealthPro, 2019b).
It is transmitted either by direct contact with an infected person or contaminated food and water. It is highly infectious and to contract the disease you only need to be in contact with a very small amount of the virus. It is passed out of the bowel in faeces and then finds its way into others via the oral route. This is usually though very close contact with someone who has the virus or ingesting contaminated food and water, either directly from the host or indirectly via sewage. This virus can also be spread through blood-to-blood contact, but this is very rare (British Liver Trust, 2022). It may occur as a very mild illness, having no symptoms. However, the disease tends to become more severe with advancing age, with a mortality rate of 2% in the over 50s (TravelHealthPro, 2019b). There are high levels of the disease in areas with poor sanitation and hygiene practices. Non-immune travellers are at risk of contracting the disease during visits to countries with high or intermediate endemicity. The risk will vary depending on length of stay and living conditions, with those visiting friends and relatives being particularly at risk (TravelHealthPro, 2019b). Hepatitis A remains the most common travel–related vaccine-preventable disease, but the incidence in travellers is declining. Back in 2017 and 2018, the vaccine was in short supply and during that time temporary recommendations were put in place to manage the shortage and give maximum cover to those at risk with limited supplies. However, at present there are no hepatitis A vaccine shortages, and it should be given to travellers in accordance to their individual risk and need (Public Health England, 2018).
The disease has an average incubation time of 28 days (possible from 15–50 days) (TravelHealthPro, 2019b), and the infected person is most infectious from about 2 weeks before symptoms appear until around a week after the first symptom. There are 4 phases, but not all patients experience all stages. Firstly, there is the incubation period (this can last 2–6 weeks), and the second stage can last about 10 days. The third stage usually lasts from 1–3 weeks but can last up to 12 weeks, and symptoms can include jaundice, dark urine, pale stools, itchy skin and enlarged and tender liver, spleen and lymph nodes. Lastly is the final stage where most people recover fully within a few months; however, it can take up to 6 months. Rarely, people can relapse or develop serious and life-threatening complications. Once a patient has fully recovered, they usually have lifelong immunity (British Liver Trust, 2019).
The hepatitis A vaccine has a paediatric (from 1 year old) and adult preparation. The standard practice is that one intramuscular injection will give cover for 1 year and ideally should be boosted 6-12 months after the first vaccine. This will give 25 years protection, but individual manufacturer's guidelines should be checked. After 25 years another booster can be considered (Travel Health Pro, 2019b). There was a combined typhoid and hepatitis A vaccine (this contained a full dose of hep A) but this has been discontinued. There are combined hepatitis A and B vaccines; these need to be individually examined as some do not have full doses of either and may require two as the primary course. The UK Health Security Agency (UKHSA) suggests that a booster can be given with success even if there is a significant delay between these vaccines, and a course does not need to be restarted even if there is a significant gap between the primary vaccination and the booster (UKHSA, 2022a). Clinical judgement needs to be made and nurses need to ensure the most up to date recommendations are followed.
Typhoid
Typhoid is known as an enteric fever and is contracted by ingesting food and water contaminated with the bacteria Salmonella enterica serovar Typhi (S.typhi) (TravelHealthPro, 2022c). Paratyphoid is a similar but different disease and there is no vaccine for this. The typhoid vaccine gives no cover for paratyphoid (TravelHealthPro, 2022c). There are approximately 11 to 21 million cases of typhoid annually and 128 000 to 161 000 deaths worldwide; this was estimated by WHO in 2018 (UKHSA, 2022b). Low-income areas have the highest infection rates, especially in locations with substandard sanitations and a lack of access to clean water. Most cases seen in the UK are travellers returning from South Asia, particularly the Indian subcontinent. However, it remains a public health concern in Central and South America and Africa as well (TravelHealthPro, 2022c).
Typhoid is passed on in the faeces of an infected person and any patient can also become a chronic carrier. This is more likely with increasing age, women and those with biliary tract abnormalities (TravelHealthPro, 2022c). The bacteria can then enter the water supply and food chain if the general sanitation and personal hygiene is inadequate. The disease has an incubation time of 10–20 days with the mild symptoms being fever, constipation or diarrhoea, abdominal pain, loss of appetite, myalgia, headache and occasionally a pink rose spot rash can be seen. There can be an enlargement of the spleen or liver in about 50% of those infected (TravelHealthPro, 2022c; UKHSA, 2022b). In total, 10–15% of typhoid cases will develop the severe disease, and if untreated 20% of these will be fatal. The symptoms of severe disease include meningitis, shock, intestinal perforation, and the disease can disseminate with multi-organ involvement. Antibiotic and supportive treatment can be used; however, there are now incidences of multidrug resistant cases, which are associated with more severe illness and death. Even when patients have recovered from typhoid, they might still excrete the bacteria in the stools. It is suggested that between 1–3% of those infected become long-term carriers and may still be excreting S.Typhi for over a year. Chronic carriers will need long term antibiotics to try to vanquish the bacteria from their system (TravelHealthPro, 2022c).
All travellers should be advised to make safe food and water choices and have good hand hygiene, as well as the vaccine if required. The typhoid vaccine may be recommended depending on their planned activities as well as the country of travel. For example, those staying with friends and family will be at high risk, as may those staying, working or eating with local communities (TravelHealthPro, 2022c). The typhoid vaccine can either be given as a singular intramuscular injection or 3 oral tablets: one taken each day on day 1, 3 and 5. The oral tablets are a live vaccine, so may not be suitable for all travellers, but may encourage or aid those who are needle-phobic. Most of the injectable vaccines can be given from 2 years old, but the oral version is from 5 years old. They all last 3 years before requiring a booster (TravelHealthPro, 2022c). The vaccine has an efficacy of 74% and immunogenicity of about 90%, making it not as effective as many of the other vaccines (Connor and Schwartz, 2005). Patients also often complain that their arm is painful and achy for a few days afterwards and about 1% will report a fever (UKHSA, 2022b). It could be suggested that, if there is a choice, this vaccine should be administered in the patient's non dominant arm.
Cholera
Cholera is an acute bacterial (caused by the Gram-negative bacterium Vibrio cholerae) infection, recognised by its profuse watery diarrhoea. It is contracted from contaminated food and water. It is endemic in Asia and Africa and globally there are still millions of cases every year and many fatalities. In 2017, there were a total of 1 227 391 cases reported to WHO and, of that, 5654 cases were reported as fatal (TravelHealthPro, 2019c). However, it is considered that these numbers grossly underestimate the true picture of this global disease. This may be due to lack of capacity for surveillance or diagnosis, or the fear of its negative impact on tourism. It is not mandatory for countries to report it to the WHO and, therefore, true numbers will not be known. Researchers have estimated the disease burden could be as large as 4 million cases a year and with up to 143 000 deaths (WHO, 2022).
Cholera can be epidemic or endemic in countries. An epidemic or outbreak can occur in either an endemic country or a country where the disease is not usually present. An endemic country is one with evidence of local transmission and that has also had confirmed cases in the past 3 years. These countries can have seasonal or sporadic outbreaks and transmission is closely linked with a lack of access to sanitation facilities or clean water. Areas that are particularly high-risk are locations where even the most basic requirements for clean water and sanitations are not being met, eg camps for displaced people or refugees, peri-urban slums or in a humanitarian crisis (WHO, 2022).
The incubation period for cholera is 12 hours to 5 days. Rehydration is the main management and without this the consequences can be dire (TravelHealthPro, 2019c). Adult patients may require up to 6 litres of oral rehydration solution in the first day. Some patients who are severely dehydrated might require hospitalization for rapid intravenous rehydration and these patients may be given appropriate antibiotics as well; however, mass administration of antibiotics is not recommended. The risk of cholera for those travelling to endemic areas is hard to determine (WHO, 2022). Around 75% of people infected will have very mild or no symptoms; therefore, many cases may go undiagnosed and be self-limiting. In most healthy travellers the illness is likely to be mild. However, those with underlying health problems, for example, compromised immune systems or liver disease are at greater risk from severe disease. Expatriates and aid workers in disaster or refugee camps or slums are probably the travellers at greatest risk of contracting cholera (Fit for travel, 2022b). Most travellers will only need to follow the advice on food and water hygiene, but for those at high risk, either by personal factors or activities, there is an oral cholera vaccine. It is in a drink preparation and two doses need to be taken with a minimum of a week between them (maximum of 6 weeks). This provides 2 years of protection (TravelHealthPro, 2019c). It can be taken from the age of 2 years, but between the ages of 2 and 6 years a third dose is required, and the preparation is slightly different. The traveller needs to have not eaten or drunk for an hour before and after the vaccine (UKHSA, 2013). Like most other vaccines it needs to be kept refrigerated, but as the patient usually takes the second dose home (and sometimes the first) this point needs to be reiterated. They should always be shown how to prepare the vaccine drink in the correct manner.
Conclusion
Prevention of food- and water-borne diseases should still play an integral part of the education and information travellers receive from travel health consultations. As discussed, taking food and water precautions and making wise choices is the key to prevention. However, in conjunction with this, vaccines are also available to help prevent these unpleasant and sometimes dangerous diseases. Nurses should be carrying out individual risk assessments, not only reviewing the itinerary and personal factors but the traveller's individual activities as well. Based on this, the appropriate vaccines to prevent food- and water-borne diseases should be recommended.
KEY POINTS
- Food- and water-borne diseases are caused by one of many organisms, including bacteria, viruses or parasites
- Contaminated food and water are key spreaders of these diseases
- The vaccine-preventable diseases are poliomyelitis, hepatitis A, typhoid and cholera, and these should be offered to those at-risk
- Food and water hygiene advice should be given to all travellers to reduce the risk of contracting all pathogens caught in this manner
CPD reflective practice
- How can you stay up to date with developments (eg polio found in sewage in London) around vaccination?
- What food and water advice would you give to travellers going to low-income countries?
- Why is this so important?