Tropical illnesses

Cholera

Cholera is a bacterial infection, which causes severe diarrhoea and can eventually lead to death through severe dehydration. The infection is spread through infected food and water, or from one infected person to another through the faecal-oral route. The incubation of cholera ranges from a few hours to five days and first presents with very bad, watery diarrhoea sometimes loosing up to a litre an hour! It is at this stage that rehydration is very important.
Any traveller to areas where Cholera is endemic (that is: the infection is present in low levels) is at risk.
The best way to prevent any diseases causing diarrhoea is to be very careful with food and water while in an endemic area. Food products that could potentially put a traveller at risk and that should be avoided include raw fish and seafood products, and any food that has been washed in potentially unclean water. Proper cooking of food and adequate boiling of water will protect the traveller from contamination through food and water. Strict personal hygiene is also essential.
Vaccination is not usually advised for travellers.

Dengue Fever

Dengue Fever (DF) is a mosquito-borne disease affecting an estimated 50 million people each year. DF occurs in all tropical and some sub-tropical areas of the world, usually in an urban setting. Today 2,5 billion people worldwide live in areas that are at risk of infection. Humans contract the disease when bitten by an infected female Aedes mosquito.
Mosquitoes remain infected all their lives and can in turn pass on infectivity to their eggs. In some parts of the world it has been seen that monkeys are also able to pass on the infection to mosquitoes. Endemic areas increase around the world due to trade (particularly tyre trade where mosquitoes breed in pools of water in tyres). After a bite from an infected Aedes mosquito, the virus circulates in the blood for 2-7 days, causing a feverish illness with headache and muscle pains similar to flu. Sometimes presents with a rash.
Any traveller to an endemic area; that is, an area where the disease is constantly present with low levels of infection. Endemicity is high in Central America, as well as in African countries such as Mauritania around to Nigeria, with patches around the Egypt and the Sudan border.
In many countries efforts are made to combat the vector through control of breeding sites. For the traveller, mosquito bite prevention is the only method of preventing DF.

Diphtheria

Diphtheria is an acute infection affecting the upper respiratory system. It is spread by droplets, which are passed through coughing or sneezing. It can also be transmitted via intimate contact with an infected person. It is a fatal disease. After contact with the disease the incubation period is about 3 days, after which symptoms occur in the form of fever, tiredness and sore throat. This develops with the production of a thick grey exudates and difficulty in swallowing.
Any traveller to an endemic area; that is: an area where the disease is constantly present with low levels of infection.
The best method of protection is vaccination. The diphtheria vaccination is part of the routine immunisation programme and is given in a combined vaccine with tetanus as a primary dose and reinforced for the purpose of travel.

Hepatitis A

Hepatitis A is spread by the faecal-oral route, person to person or through contaminated water or food. It is the second most common infection in travellers. Blood borne transmission occurs but is very rare.
It is a viral infection, which can be silent. The incubation period is 15-50 days followed by no signs, or pyrexia, headache, nausea, vomiting, abdominal discomfort for 2-7 days. Urine darkens and stools pale as the patient moves into a jaundice phase. Fever then resolves and the patient is no longer infectious. Recovery can take several months.
Hepatitis A is seen worldwide. Areas of high risk are Central and South America, Africa and Southern Asia out to Indonesia.
Vaccination, or screening for antibodies in those over 40 years of age, is the best and most effective way of preventing Hepatitis A. Even with vaccination, travellers should be aware of good food and water hygiene. Avoiding potentially contaminated food and drink can prevent most cases of Hepatitis A among travellers. The disease is often considered asymptomatic in those under the age of 10 and vaccination is often discouraged. However, it is important to understand that transmission can still occur and therefore vaccination should still be considered where the risk of infection is high.

Hepatitis B

Hepatitis B is the third most common infection in travellers. It is a disease, which affects the liver. It is 100 times more infectious than HIV and can survive in dried blood for up to seven days. It is spread from person to person through contact with bodily fluids i.e. semen, saliva, tears, vaginal fluid or urine and blood.
Symptoms of the diseases range from an asymptomatic response, to flu like symptoms and a general feeling of unwell. At this stage many recover from the disease, however some go on to develop abdominal pain, jaundice which can last up to eight weeks. At this stage a person will either produce antibodies to the virus or go into full liver failure, which can result in death.
Hepatitis B is found worldwide. Areas of high endemicity include Tropical Africa, South America, Southeast Asia, Parts of China and the Pacific Basin, where a carrier rate is estimated to be 8% of the population. High-risk groups in travellers include those who are health workers, haemophiliacs, injecting drug users or practising homosexuals.
Vaccination is available for those at risk and should be discussed with a health care provider. For routine travel to high-risk areas a cost is usually incurred and prices will vary from place to place. All travellers whose lifestyle puts them at risk should consider vaccination. Personal prevention is also essential, such as avoiding tattoos, dental treatment or other practices which involves puncturing the skin. Backpackers and those working long term overseas should consider carrying with them a medical kit.

Human Immunodeficiency Virus (HIV)

HIV is a virus. HIV is spread in travellers via sexual contact with an infected partner, through infected blood transfusions and infected blood products, and via contaminated needles. Infection with the virus can leave a person asymptomatic. Alternatively symptoms can occur within 4-12 weeks of coming into contact with the virus.
The symptoms closely resemble glandular fever and are known as the prodrornal seroconversion illness, as the body begins to develop antibodies. Some people also develop a rash at this time with a temperature. After this period the virus can remain dormant for up to 15 years when the CD4 count begins to drop and lymphadenopathy develops.
HIV infection can resemble many symptoms and eventually, when the immune system is unable to cope, AIDS infection occurs. After diagnosis of AIDS, death often occurs within 20 months.
HIV is a global problem. Once predominant in Africa, it is now present worldwide. Those who work with blood products in their occupation are at high risk, as are those who choose to engage in practices that increase the risk of infection. Most new infections occur in developing countries with areas of highest risk being Africa and Southeast Asia.
Currently we have no vaccination for protection against HIV and the best method of prevention is personal protection. Personal prevention is essential, such as using a condom when engaging in sexual activity, avoiding tattoos, dental treatment or other practices which involves puncturing the skin, or using equipment which may have been inadequately sterilised.

Preventing Malaria

Malaria is an increasing problem around the world. In part this is caused by changing global temperatures and drug resistance. Millions of people die from Malaria each year and it is increasingly becoming an ongoing problem for the traveller to the Malaria zones of the world.
Climate greatly affects the feeding and breeding habits of the malaria mosquito. It is prevalent in tropical climates, but usually not higher than 1,500-2,000m above sea levels. Mosquitoes breed only in fresh water. World climate and global warming affect breeding and the spread of malaria. A countrywide change in 2°C can affect numbers of malaria cases over a season.
Most medication is taken for a set period before going, continued while you are in a malaria zone and for a set period on return.
If you suffer from any heart condition, are pregnant, breast-feeding or epileptic, it is important that you inform your travel health advisor as this might influence the medication you are given.
Mosquitoes feed between dusk and dawn. The mosquitoes tend to respond to light in their feeding habits and are most active in low light hours after dusk and in the hours prior to dawn. Female mosquitoes will take a blood meal just before laying their eggs, which are laid at night. It is therefore important that repellents are used between dusk and dawn to prevent being bitten.
Use a repellent that has DEET, or contains a natural repellent such as lemon and eucalyptus; try to avoid using products that are connected to homemade concoctions!
While clothing alone will not protect you against mosquito bites, it can help in preventing bites when used along with other careful prevention. Clothing that covers the body, such as long trousers and long sleeves; socks etc., worn after dark will lower the risk of being bitten. While mosquitoes are able to bite through many materials, canvas mosquito boots and thick denim jeans will make it more difficult.
Clothing that has been impregnated with permethrin will also help repel mosquitoes. This clothing along with impregnated wrist and ankle bands lower the risk of being bitten.
If you are reluctant to impregnate everyday clothing, impregnated netting worn over the clothing will prevent chemical contact with the skin. It is important that fellow travellers are protected in a similar way, as repelled mosquitoes will go to another person who is not protected!
Research has suggested that mosquitoes are attracted to sweat and so keeping clothes clean, especially socks (!), might help. It has also been suggested that mosquitoes are attracted to dark colours, so wearing light colours or white clothing might help prevent being bitten.
While air conditioning does help keep the mosquitoes away due to the lower temperature, it is important that it is left on all day and that the windows are not left open at night!
Using a mosquito net in an area where malaria is present is a good idea. Ideally the net should be impregnated with permethrin at least every six months or when it is washed.

Polio

Polio is a disease that primarily affects the nervous system. It is spread via the faecal-oral route from person to person and can also be transmitted via dirty food and water. Polio is eradicated from most areas of the world after an intensive vaccination programme.
Polio has an incubation period of about 7-14 days, after which around 90% of cases show no symptoms, producing a lifelong immunity. Others, however, display a flu-like illness and then recover, while about 1 in every 1000 cases of the illness develops a paralytic illness affecting the nervous system, which sometimes leads to death.
Any individual who has not been vaccinated and is travelling or working in an area where Polio is endemic, is at risk of Polio. After an intensive worldwide vaccination programme Polio has been eradicated from most countries. Areas in which Polio is still endemic include areas of Africa and Asia.
Polio vaccination is part of the national vaccine recommendations. A course of vaccine is usually started when a child is one month old, given a month apart for three doses. A booster is then given at school entry as part of the pre-school booster, and then again at leaving age around 15-19 years of age. Adults are then given a booster dose if they are travelling, every ten years. Even with vaccination, travellers should be aware of good hygiene.

Rabies

Rabies is a disease transmitted to humans via the bite of an infected animal. Rabies is an acute viral infection, which affects the central nervous system. Symptoms usually begin with a fever, followed by symptoms such as agoraphobia, hallucinations, convulsions and other disturbing behaviour. Untreated rabies always results in death, usually by respiratory paralysis.
Rabies is endemic (that is: infection is present in low levels) in all areas of the world.
For those travelling to high-risk destinations vaccination is the best method of protection. Advice should be sought from a health professional in regard to vaccination. Vaccination prior to travel is often regarded unnecessary for those less than 24 hours away from a vaccine supply. However, vaccination might be advisable for those travelling to areas where supplies of rabies immunoglobulin are currently known to be low even if they are less than 24 hours from medical attention.
It is also essential that travellers avoid stray animals in risk areas.

Schistosomiasis

Flukes, whose life cycle requires fresh water snails, cause Schistosomiasis. Schistosomiasis is contracted through the skin from fresh water contaminated with urine or faeces of an infected person. It is second only to Malaria as a public health problem in tropical and sub-tropical areas, affecting approximately 200 million people in both rural and peri-urban areas. 500-600 million people worldwide are at risk of the disease. Refugee movements in Africa cause spread to wider areas.
Travellers might experience an itching or rash a few hours after contact where the larvae enter the body. A person may remain symptom free until the eggs hatch weeks later, when a fever sometimes occurs. One of 5 types of fluke cause an infection of the bladder and/or bowel, often with bleeding. There are also recent reports of paralysis of the legs.
Any traveller to areas where Schistosomiasis is endemic is at risk. This includes South America, Africa and parts of the Middle East and India, and in Asia. Caution should be taken with diving lessons in fresh water lakes in risk areas!
Travellers should not paddle or swim in fresh water lakes, streams, rivers or slow running water. Quick drying of exposed areas can offer some protection, due to larvae needing water to survive. Minimal protection is also gained from wearing rubber boots or wet suits.

Tetanus

Tetanus is caused by a bacterium most often found in the soil, but spores can also be found in the faeces of domestic animals. Tetanus is usually contracted through minor wounds and burns, most frequently during the summer months or in warm climates. After an incubation period of around 12 days the disease affects the nervous system, causing muscle spasms and rigidity. This can eventually lead to respiratory failure and death.
Tetanus spores are found all over the world.
The best method of protection is vaccination. The tetanus vaccination is part of the routine immunisation programme and is given in a combined vaccine with diphtheria as a primary dose and reinforced for the purpose of travel.

West Nile Virus

West Nile Virus (WNV) is a virus spread primarily through the bite of an infected mosquito. The virus usually circulates among birds and mosquitoes. Animals and humans are only occasionally infected.
In most cases the virus causes mild flu like symptoms 3-14 days after the bite from an infected mosquito. Other symptoms might include eye pain, vomiting and a rash on the skin. These symptoms usually last 3-6 days.
Only 1 in 150 infected persons can go on to develop a more severe form of the disease, with increased age (over 50) being an indicator for higher risk. Severe symptoms include fever, weakness, vomiting and a change in mental behaviour. These symptoms can eventually lead to death.
Up until 1999 this disease was mainly found in Africa, Egypt, South-east Asia and the Southern parts of France. The first recorded cases in the Western Hemisphere were reported in New York in 1999 and since 2000 many cases have been reported throughout the United States and Canada. Any person travelling to these areas is at risk of the disease.
Risk is seasonal in most places and will therefore vary at different times of the year.
There is no vaccine to prevent WNV in those travelling to high-risk areas. Prevention of bites from mosquitoes is the best line of protection. Most of the mosquitoes bite from dusk to dawn and a good repellent should be used during this time, however in some areas day biters have been found so use repellent accordingly.

Yellow Fever

Yellow Fever is a virus, which is spread via the bite of an infected mosquito. It is found in tropical areas of Africa and South America.
Yellow Fever is recognised in two different forms - urban and jungle. Urban Yellow Fever occurs in the cities and is spread from mosquito to human to mosquito. In the jungle form Yellow Fever is spread from mosquitoes to monkeys and also to humans.
The disease presents itself after an incubation period of about 3-6 days with flu like symptoms, with death occurring in around 5% of those who become infected. There is no treatment for Yellow Fever, and so relief of symptoms is the primary course of action.
Any traveller to areas where Yellow Fever is endemic (that is: the infection is present in low levels) is at risk. This includes areas of Africa and South America.
Travellers should obtain the necessary vaccination when travelling to endemic areas of the world. Confusion still exists as to which countries require a compulsory certificate against Yellow Fever. A Yellow Fever certificate is the ONLY internationally regulated certificate. The WHO recommends it for all travellers to endemic areas, as well as for those coming from an endemic area to an area of potential transmission. The purpose of the certificate is not only to protect the traveller but to also protect those in areas of the world where infection is possible due to the presence of the Ades mosquito. It is essential to ensure that the traveller plans ahead due to the shortages of vaccine at this present time.

Typhoid

Typhoid is a bacterial infection of the digestive tract, caused by gram-negative bacillus Salmonella typhi. It is spread by faecal-oral route via contaminated food and water from an infected human carrier. Typhoid is often transmitted by person-to-person contact, especially via food handlers. Incubation is 1-3 weeks and is rare under 2 years of age.
Symptoms usually appear over the course of a month, with headaches and lethargy progressing to myalgia and abdominal discomfort. Some patients show a 'rose spot' rash after the first week of infection. Constipation can occur followed later by bloody diarrhoea with rigors. Patients remain infective for 6 weeks to 3 months after infection.
Typhoid is present in South America, Africa and areas of Asia, with undeveloped areas being of a higher risk. Cases can potentially occur throughout the world due to the mode of transmission and speed of travel.
Vaccination (injectable or oral) for risk areas and occupational risk should be considered. Vaccination against both Hepatitis A and Typhoid combined is also available for travellers, as the two diseases have a similar epidemiology and share some transmission routes. As vaccination does not offer 100% protection, avoiding potentially contaminated food and drink is essential.