Many travel health risks remain under-recognised, so several important updates—and a few misconceptions—are worth revisiting, experts say.

Rabies, an underestimated travel risk

Rabies is universally fatal, making prevention critical—but the risk of contracting it is often underestimated, says Dr Bernard Hudson, Senior Staff Specialist in the Department of Microbiology and Infectious Diseases, Royal North Shore Hospital.

While a lot of people don’t think they’ll get exposed to rabies, vaccination should be recommended more widely, he stresses.

Dr Deb Mills, Medical Director of the Travel Medicine Alliance, agrees.

Although Australian Bat Lyssa Virus (ABLV) is found in flying foxes and insectivorous bats (microbats), there’s no rabies in Australia, “so Australians are often blissfully unaware of it,” she explains. But in many countries that Australians frequent—like Indonesia and Thailand—rabies is endemic in animals such as dogs, monkeys and cats.

Even “the tiniest bite, the size of a pinprick,” can lead to infection, and standard post-exposure treatment is “horrendous”, she says.

“You’ve got to go and get a blood product (RIG) injected in the wound on the day of the bite. Getting hold of that product can be extremely difficult. This product has a very short expiry date. It’s very expensive. And then you need the Rabies vaccine on day zero, three days later, seven days later, 14 days later and probably 28 days later. It’s a huge disruption to their happy trip.”

Pre-travel vaccination simplifies management considerably. “If someone is immunised before they go and they do get a potential exposure the traveller has more time to get to a doctor. And they only need the vaccines. They don’t need the RIG blood product injected in the wound.”

Previously three doses of rabies vaccine were required, but an abbreviated schedule is available.

“Now you only need two doses before travel,” Dr Mills says. “Day zero and day seven.”

She advises people planning to visit rabies-endemic areas to stay well away from dogs, monkeys and cats. “Think of them like snakes. Don’t be within lunging distance.”

When considering whether to get the rabies vaccination Dr Mills recommends “thinking about the lifetime risk, not just one trip.”

Dengue fever prophylaxis

Mosquito bite prevention measures are the most important way to reduce the risk of dengue fever.

The previous dengue fever vaccine, Dengvaxia, has been withdrawn from the market following the deaths of children in Thailand and the Philippines who developed dengue haemorrhagic fever.

Another live attenuated vaccine, Qdenga, is available through the TGA’s Special Access Scheme on a case-by-case basis, despite not being registered in Australia. It may be considered for people aged 4 and older who have had Dengue fever before and who will continue to travel to a dengue endemic area or may be travelling during an outbreak.

Japanese encephalitis

Noting its high rate of mortality and morbidity, the Australian Immunisation Handbook (AIH) recommends vaccination against Japanese encephalitis (JE) for anyone who will be staying in an endemic region overseas during transmission season for a month or more, and considering it for shorter stays if there are other risk factors (e.g., travel during the wet season, to at-risk rural or agricultural areas, or if travellers will be staying in accommodation without mosquito protection or taking part in a lot of outdoor activities).

Mosquito‑avoidance is also key to JE prevention.

“JE is rare but catastrophic,” Dr Mills emphasises. “Rare does not mean never and JE should be discussed with travellers visiting endemic areas – the tool https://www.vaxical.com can help decide on risk.’

Mosquito repellents

Mosquito bite prevention reduces the risk of several infections, and the CDC recommends three categories of repellent, Dr Hudson says. DEET is the gold standard—but has a plasticising effect. “It will melt synthetic materials, including clothing.” Alternatives include picaridin (also called icaridin) and extract of lemon eucalyptus (Corymbia citriodora). Other “natural” products may have repellent properties, but only those with an Australian Pesticides and Veterinary Medicines Authority (APVMA) number have demonstrated efficacy and safety.

Regardless of their vaccination status, travellers should use measures including repellents, protective clothing, avoiding areas with obvious mosquito activity, and accommodation with screens or air conditioning to avoid mosquito bites.

Sleeping during the day can also increase the risk of Dengue fever, as it is transmitted by day-biting mosquitos, Dr Mills says.

Travel can trigger shingles

The pressures of travelling can sometimes reactivate the varicella-zoster virus, ruining someone’s trip, Dr Mills says.

“It’s lurking in the nerve endings from childhood, and travellers cross time zones, hang around in airports, and suffer jet lag, lost bags, or cancelled flights —events that cause stress. Then they get shingles, and the worst possible time to get it is when you’re travelling.”

While the vaccine is funded under the National Immunisation Program for Australians aged 65 years and over, many eligible patients have not had it, she says.

It is also recommended—although not government-funded—for people over the age of 50.

“Yes, it’s expensive, but days in hospital are also expensive,” she says, noting evidence that the shingles vaccine may also decrease the risk of dementia and severe pain from damage to the nerves.

“I think it’s worth discussing with every patient over the age of 55.”

Supermarket product can help prevent traveller’s diarrhoea

Diarrhoea is the most common illness affecting international travellers, but rising drug resistance among gastrointestinal pathogens makes treatment more challenging, Dr Hudson says. “And we know that if you actually take antibiotics when you’re overseas, you’re more likely to come back with a multi-resistant gram-negative organism in your gut.”

An alternative to be aware of is Travelan, which contains antibodies derived from the colostrum of New Zealand dairy cows. It targets the toxins produced by enterotoxigenic Escherichia coli (ETEC)—the most common cause of travellers’ diarrhoea, but it also has broad activity against some other common gastrointestinal pathogens.

Early studies showed that compared to placebo, Travelan significantly reduced incidence of diarrhoea among participants exposed to ETEC.

Dr Mills says the vaccine Dukoral works in the same way as Travelan “and may be more convenient for some travellers as you can take it before departure and then forget about it.”

For gastrointestinal infections, Dr Hudson suggests vaccinating against typhoid, hepatitis A and cholera when appropriate, and considering Travelan as well. It is available from supermarkets and pharmacies and needs to be taken before each meal.

Malaria prophylaxis options

Dr Hudson says people visiting a rural malaria-endemic area who will be sleeping in non-air-conditioned accommodation probably need malaria prophylaxis.

Several options exist, each with advantages and limitations.

Doxycycline is inexpensive and has antimicrobial activity, he explains. “So it protects you against a lot of other things—like rickettsial infections and leptospirosis—which do occur in travellers. Its downside is that in women, it increases risk of candida vaginitis.”

It also increases photosensitivity, “so you’ve really got to protect yourself against the sun,” he adds.

Another daily option is atovaquone 250 mg/proguanil hydrochloride 100 mg (Malarone), which needs to be taken daily with food containing fat; “something like a milk drink or buttered toast,” Dr Hudson says.

“And it’s recommended to be continued for seven days after you return, but there’s a lot of literature that suggests that if you run out of tablets and you take it up to and including the last day of your trip, or the day after you leave the malaria area, it’s probably still going to work.”

Malarone dose for children depends on weight and is available in a ‘junior’ version, (atovaquone 62.5 mg/proguanil hydrochloride 25 mg) for children who weigh 11kg or more.

A newer addition to malaria prevention is tafenoquine (Kodatef), which is approved for up to six months of continuous use in adults 18 years and over.

“You take a loading dose of 200 milligrams a day for three days,” Dr Hudson explains. “And then you just take 200 milligrams once a week while you’re away. Then once you return from the malaria endemic area, you take it seven days after the last dose.”

Weekly dosing can suit longer-term travellers, such as volunteers or aid workers spending extended periods in malaria-endemic regions, he says.

However, you need to run quantitative testing for glucose-6-phosphate dehydrogenase (G6PD) deficiency before prescribing tafenoquine, as it can induce severe haemolytic anaemia in individuals with this deficiency.

Neither Malarone nor tafenoquine is approved for use in pregnancy, he adds.

“The reality is if you’re pregnant, you’re probably better off not going to a malaria endemic area.”

Don’t Forget TB

Consider BCG in travellers are under age 5 going to visit friends and relatives in high TB risk countries.

Protecting travellers from measles

With the global comeback of this vaccine-preventable illness, anyone planning travel should have their measles immunity status reviewed, Dr Hudson says. In people born after 1966, look for documented evidence that they have had two doses of measles-containing vaccine or prior infection.

The Australian Technical Advisory Group on Immunisation now recommends infants aged 6 to 11 months who will be travelling overseas should have an extra dose of a measles-containing vaccine, but they will still need to have the standard 2-dose schedule when due.

Seek advice from a specialist in patients who are immunocompromised.

Influenza

Dr Mills notes respiratory infections can spoil trips people have spent thousands of dollars on. She recommends ensuring travellers are up to date with appropriate vaccines and advising them to wear an N95 mask in high-risk environments, especially poorly ventilated, crowded parts of airports.

She also suggests they carry a rapid antigen test that can detect COVID-19, influenza A and B, and respiratory syncytial virus, which are sold in supermarkets and pharmacies.

This enables travellers to determine the cause of their symptoms and access antiviral treatment where appropriate.

More information

Journal of Travel Medicine | Travel vaccines—priorities determined by incidence and impact

Australian Journal of General Practice | Protecting travellers from vaccine-preventable diseases