The theme of the Conference of the International Society of Travel Medicine I attended in June was Travel Medicine in a Changing Climate. We heard depressing statistics about how climate change exacerbates existing threats and acts as a threat multiplier and particularly affects people living in marginal areas who are already vulnerable. Disasters caused 61 % of the 28 million displacements that occurred last year. Interactions between climate and infections are very complex and poorly understood. For example, with increasing temperatures in Africa malaria may decline and dengue increase as the optimal temperatures for the different mosquitoes that transmit the two illnesses differ.
A more encouraging speaker was the one on Making Tourism Sustainable. She told us about the Global Sustainable Tourism Council (GSTC) which is a non-profit organisation which recognises that tourism has the potential to do harm but endeavours to make tourism beneficial. It has established Global Sustainable Tourism Criteria. These are “the guiding principles and minimum requirements that any tourism business or destination should aspire to reach in order to protect and sustain the world’s natural and cultural resources, while ensuring tourism meets its potential as a tool for conservation and poverty alleviation.” Before we travel we should think about our destination and activities carefully. We should think about our mode of transport and if flying offset our carbon. Is our accommodation or tour operator GSTC accredited? Pack lightly to reduce our carbon and take reusable drink bottles and coral safe sunscreens. We should learn some local language, pay the price (not haggle) and respect the natural environment.
Measles cases are rising alarmingly in many areas but I wrote about that last July. I am thus going to discuss the increased risk of dengue in many popular tourist destinations. Dengue comes in waves every few years. Cases are currently increased in Vietnam and Singapore is having an outbreak. Dar es Salaam in Tanzania is as well. Closer to home Timor Leste, Palau, Vanuatu, New Caledonia, Tuvalu, French Polynesia and Cook Islands have increased numbers of cases. Fiji may too as travellers have been diagnosed after trips there recently.
Mosquito bite avoidance is the only protection against dengue. It is day biting ones that are responsible and they may be in urban areas as the out break in Singapore illustrates. The first dengue vaccine in use has now been approved in America for people with a documented prior dengue illness who live in dengue areas. There are more dengue vaccines in the pipeline so in the future vaccination may become a strategy for travellers. Until then use your repellent.
Unfortunatley we currently have a rabies vaccine shortage in New Zealand. This is causing some restrictions on preexposure prophylaxis. Remember that mammal bites in most countries of the world carry a risk of rabies and should be avoided. Travellers are more likely to be bitten in Asia than Africa or the Americas as there are many opportunities to mix with dogs and monkeys. The risk of a mammal having rabies is highest in Africa as dog vaccination there is low. Dog bites are the most common followed by monkeys. Children are more likely to be bitten than adults and as their bites are often on the face which has many nerves the bites are a higher risk.
Always keep away from pets especially those eating, sleeping or with babies. Avoid contact with free roaming mammals and stay away from bats. Don’t try to run away from dogs but stand still and avoid eye contact. If you fall over curl up and stay still. It is better not to visit monkey beaches or temples and if you do certainly don’t take any food with you. Again, staring them in the eye is a sign of aggression. Many bats have tiny teeth and wounds may not be readily apparent. Any suspected or documented bite or wound from a bat is a reason for seeking post bite treatment.
If bitten or scratched by a mammal wash the injury with copious amounts of water and finish with something like betadine. Then seek medical care as soon as possible. Vaccination with cell cultured vaccines following a WHO approved schedule should be started and in addition WHO category 3 injuries (single or multiple transdermal bites or scratches, contamination of mucous membrane or broken skin with saliva from animal licks, exposures due to direct contact with bats) should be injected with rabies immunoglobulin. This may not be available at the first medical centre you go to but you should go somewhere bigger until you find some. Thailand is a country with excellent post bite management so although many people are bitten there deaths from rabies are low.
Pretravel rabies vaccines make it easier if someone is bitten. They already have antibodies so just need 2 doses of vaccine to boost their protection after an injury and don’t need immunoglobulin. Remoteness from healthcare, planned activities and duration of travel are all factors to consider when deciding whether to be vaccinated before travel.
In the past Venezuela was admired for its healthcare system and public health infrastructure. Unfortunately, the past few years have changed that. There is now food insecurity with malnutrition, the health care system has collapsed and there has been a massive exodus of health care workers. Infant and maternal mortality have increased and infectious diseases previously controlled or eliminated have returned. The flow of people from Venezuela to neighbouring countries is affecting their rates of infectious diseases too. For example, the continent had controlled measles however between January and December of last year there were over 5,600 cases in Venezuela, more than 2,000 cases in Colombia and over 10,000 in Brazil. Those in Colombia and Brazil were linked with Venezuelan migrants. There have been 1,000 cases of diphtheria (another vaccine preventable disease essentially eliminated) since January 2018 in Venezuela. In 1961 WHO recognised Venezuela for eliminating malaria in densely populated areas. The past few years have seen a resurgence. Between 2015 and 2016, reported cases increased by over 75%, from 136 402 to 240 613. There is a severe shortage of antimalarials and control efforts have stopped. HIV and TB are other infectious diseases increasing and being taken by migrants to neighbouring countries. These two diseases need good medical care to treat patients and to reduce spread. The current situation is thus a huge crisis which needs urgent attention for the health of the region and of those who travel there .
Prior to 2014 Ebola outbreaks were usually small and in remote areas and thus controlled relatively easily once recognised. The outbreak in 2014, however, occurred in urban areas and caused nearly 30,000 cases and over 13,000 deaths. In addition, the World Bank estimated that the West Africa epidemic cost the three affected countries $2.2 billion in lost gross domestic product in 2015. Ebola is again spreading in urban areas, this time in the Democratic Republic of the Congo. Since September, the incidence of Ebola has more than doubled and the outbreak is now the second largest one to date. The virus has spread to 11 DRC health zones, and the WHO has deemed the risk of further national and regional spread to be very high. The majority of people with recently diagnosed Ebola were not on existing lists of contacts of people with the disease. This concerningly indicates unrecognized transmission in the community. Control efforts are being hampered by civil unrest, armed conflict, inadequate infection prevention and control in healthcare settings and community resistance. No cases have been reported in neighbouring countries to date but if the outbreak continues the risk of spread is high particularly to Uganda and also Rwanda and South Sudan. Heightened surveillance has been implemented in Burundi, Rwanda, South Sudan, and Uganda. Unlike previous outbreaks vaccination is being trialed with over 53,000 people being vaccinated in affected areas. In addition, experimental treatments are being used.
Sexual transmission may occur even in men with no symptoms of the infection. Previously it was recommended that men who have travelled to zika areas abstain or use condoms for 6 months to avoid infecting their partners. This was based on finding virus material in semen for more than 3 months in some cases. Newer information shows that live virus stops being in semen by one month usually. The new recommendation is: that men with possible Zika virus exposure who are planning to conceive with their partner wait at least 3 months after symptom onset or their last possible Zika virus exposure before engaging in unprotected sex. This applies to all sexual partners even those not planning pregnancy.
To check the latest information about risk countries see: www.who.int/emergencies/zika-virus/classification-tables/en/
Twelve laboratory-confirmed cases of circulating vaccine-derived poliovirus type 1 have been diagnosed since late April in Port Moresby (1 case) and in the provinces of Eastern Highlands (4 cases), Enga (2 cases), Madang (2 cases), and Morobe (3 cases). The most recent was on August 2. One clinical case of polio often represents hundreds of infections in the population with out symptoms. Risk to travelers is negligible but an adult booster of inactivated polio vaccine for all travelers going there is recommended (in addition to a past a primary series).
Papua New Guinea has not had a case of wild poliovirus since 1996, and the country was certified as polio-free in 2000. In response to the cases 4 rounds of large scale immunisations campaigns have been started to vaccinate children under 5 years.
Many travellers think that preparation for a healthy trip just involves vaccinations. In reality, the vaccine preventable diseases are a much less frequent cause of ill health than diseases we cannot vaccinate against such as diarrhoea, skin problems, malaria and dengue. Similarly, deaths during travel are most commonly the result of heart attacks or accidents, not vaccine preventable diseases.
A recently updated graph of vaccine preventable diseases still puts influenza at the top of the list for vaccine preventable illnesses in travellers (1 in 100). It is particularly sensible for those travelling in groups, on cruise ships and the elderly to have one before travel. Animal bites with a risk of rabies (3 in 1,000) are next then typhoid in South Asia (2 in 10,000) followed by hepatitis A (1 in 10,000). Tick borne encephalitis, measles and hepatitis B are the next occurring in 3 or more per 100,000 travellers to risk areas. While the risk of yellow fever has traditionally been low in travellers this has changed with around 30 cases seen in the past 2 years during outbreaks in Angola and Brazil.
Make sure you have had 2 doses of measles vaccine (MMR) before travel as cases are up in many areas around the world. If you were born prior to 1969 you should be protected against it as the virus was circulating prior to then. Those born since then should be sure they have had 2 doses as one does not protect everyone. Currently the MMR vaccine is given at 15 months and 4 years of age. Unfortunately, the false autism scare seriously knocked confidence in the vaccine so many people were not vaccinated and in order to keep measles rates low vaccination rates of 95% are needed. The vaccine is a live vaccine so pregnant women and those with weakened immune systems should not have it. Live vaccines should be given together or 28 days apart so don’t have it just before getting a yellow fever vaccine or the shingles vaccine.
Venezuela has recorded 1613 measles cases and 44 deaths this year and other countries in Latin America have cases linked to Venezuela. For example, Brazil has had nearly 700 cases in 2018 and Argentina has had cases despite not having any local measles since 2000. This year in the UK 757 cases of measles have been reported compared with 274 cases reported in the whole of 2017 and 3 deaths due to measles have been reported in France this year.
Returning travellers bring measles back to their home countries and start out breaks. This year an unknown person must have passed through Queenstown airport when infectious with the virus as a cluster of cases among people who had been in the airport at the same time as each other developed measles. The same thing has been noted in Japan a number of times recently including 91 cases diagnosed in Okinawa after an infectious person visited the island.
The past influenza season in the northern hemisphere saw very high rates of illness, hospitalisations and deaths. A recent study on influenza showed that on average 1 in 5 unvaccinated children and 1 in 10 unvaccinated adults are infected with seasonal influenza annually. Half of those infected have typical symptoms of influenza. Rates are highest in children, followed by older people, and lowest in adults. Vaccine efficacy varies considerably each season depending on if the vaccine matches the circulating strains well or not. The match for the past northern hemisphere vaccine was not good so protection was estimated to be only 36%. We have a different component in our vaccine for this season and hope it will match the strains we get. I encourage you to have an influenza vaccine and also remember that in the tropical parts of the world influenza circulates year round.