Vector-borne diseases are infections transmitted by insects and animals that harbor parasites, viruses, or bacteria. Common vector-borne diseases include yellow fever and malaria, but there are many others in every country in the world.
The risk for malaria and other mosquito-born infections is highest when mosquitoes feed, between dusk and dawn.
DEET. Most insect repellents contain the chemical DEET (N,N-diethyl-meta-toluamide), which remains the gold standard of currently available mosquito and tick repellents. DEET has been used for more than 40 years and is safe for most children when used as directed. Comparison studies suggest that DEET preparations are the most effective insect repellents now available.
DEET concentrations range from 4 - 100%. The concentration determines the duration of protection. Experts recommend that most adults and children over 12 years old use preparations containing a DEET concentration of 20 - 35% (such as Ultrathon), which provides complete protection for an average of 5 hours. (Higher DEET concentrations may be necessary for adults who are in high-risk regions for prolonged periods.)
DEET products should never be used on infants younger than 2 months. According to the Environmental Protection Agency (EPA), DEET products can safely be used on all children age 2 months and older. The EPA recommends that parents check insect repellant product labels for age restrictions. If there is no age restriction listed, the product is safe for any age. The American Academy of Pediatrics recommends that children use 30% DEET concentration. In deciding what level of concentration is most appropriate, parents should consider the amount of time that children will be spending outside, and the risk of mosquito bites and mosquito-borne disease.
When applying DEET, the following precautions should be taken:
- Apply only enough to cover exposed skin.
- Do not apply too much and do not use under clothing.
- Do not apply over any cuts, wounds, or irritated skin.
- Parents or an adult should apply repellent to a child instead of letting the child apply it. They should first put DEET on their own hands and then apply it to the child. They should avoid putting DEET near the child's eyes and mouth, and also on the hands (since children frequently touch their faces).
- Wash any treated skin after going back inside.
- If using a spray, apply DEET outdoors -- never indoors.
- Do not apply spray repellents directly on anyone's face. Spray your hands and use them to apply DEET to your face.
Other Insect Repellent Products. In 2005, the U.S. Centers for Disease Control (CDC) added two new mosquito repellents to its list of recommended products: Picaridin and oil of lemon eucalyptus. Picaridin, also known as KBR 3023 or Bayrepel, is an ingredient that has been used for many years in repellents sold in Europe, Latin America, and Asia. A product containing 7% picaridin is now available in the United States. Picaridin can safely be applied to young children and is also safe for women who are pregnant or breastfeeding. According to the CDC, insect repellents containing DEET or picaridin work better than other products. In scientific tests, oil of lemon eucalyptus, also known as PMD, worked as well as low concentrations of DEET. However, oil of lemon eucalyptus is not recommended for children under the age of 3 years.
Use of Permethrin. Permethrin is an insect repellent used as a spray for clothing and bed nets, which can repel insects for weeks when applied correctly. Electric vaporizing mats containing permethrin may be very helpful. A permethrin solution is also available for soaking items, but it should never be applied to the skin. Side effects from direct exposure may include mild burning, stinging, itching, and rash, but in general, permethrin is very safe and its use may even reduce child mortality rates from malaria. Travelers allergic to chrysanthemum flowers or who are allergic to head-lice scabicides should avoid using permethrin.
Other Preventive Measures against insect-borne Diseases:
- Wear trousers and long-sleeved shirts, particularly at dusk. One survey suggested that this measure may significantly reduce the incidence of mosquito-borne disease.
- Sleep only in screened areas.
- Air-conditioning may reduce mosquito infiltration. Where air-conditioning is not available, fans may be helpful. Mosquitoes appear to be reluctant to fly in windy air.
- Do not wear perfumes.
- Minimize skin exposure after dusk.
- Wash hair at least twice a week.
Burning citronella candles reduces the likelihood of bites. (Indeed, burning any candle helps to some extent, perhaps because the generation of carbon dioxide diverts mosquitoes toward the flame.) Smoke from burning certain plants, including ginger, beetlenut, and coconut husks, have also reduced mosquito infiltration, but the irritating and toxic effects on the eyes and lungs (such as with the citrosa plant) may be considerable. To date, no evidence shows much benefit to burning plants but such methods are not harmful.
About a third of the population is susceptible to motion sickness, with varying degrees of severity. The cause of motion sickness is still unclear. Some evidence suggests that, in susceptible people, motion triggers signals that the brain interprets as being in conflict with the brain's memory of correct position. It transmits this message to other parts of the body, which respond with sweating, nausea, salivating, and other symptoms of motion sickness. Other theories suggest that motion sickness is triggered by the body's inability to control its own posture and movement.
More women than men experience motion sickness. Women appear to be at higher risk just before and during menstruation. Motion sickness may also trigger migraines, even in people who do not ordinarily have them. Alcohol intake increases the risk of vomiting. The following are some remedies tried for motion sickness:
Medications. Prescribed medications include scopolamine as a patch (Transderm Scop), which is worn behind the ear and releases the drug slowly. Scopolamine is the most effective drug for motion sickness.
Over-the-counter medications include dimenhydrinate (Dramamine), meclizine (Bonine), and cyclizine (Marezine). Dramamine appears to be the most rapidly effective, although in one study Marezine caused less drowsiness and was more effective at reducing nausea after 3 minutes. Cinnarizine (Stugeron) is used in Europe and appears to be effective, with few side effects. It is not available in the US. None of these medications are as effective as prescription drugs but may be helpful for 6 - 12 hours. To ensure the drug achieves its desired effect, take oral medications at least an hour before traveling.
Nearly all the medications used for motion sickness, both prescription and nonprescription, can cause drowsiness, mouth dryness, and blurred vision. Scopolamine can cause heart rhythm disturbances. In one comparison study the scopolamine patch and cinnarizine had the fewest adverse effects on functioning. Dimenhydrinate had the most.
Non-medicinal Treatments. Common recommendations include focusing the eyes on the horizon (not on nearby areas), and avoiding alcohol and strong odors. Non-medicinal or alternative remedies are widely used, but are of unproven benefit. Some methods that have been tried include:
- Taking ginger root capsules (2,000 mg) or eating large amounts of ginger starting about 12 hours before traveling. (Clinical studies are inconsistent on ginger's benefits, with some reporting relief without side effects.)
- Acupressure (wrist bands and self pressure). Acupressure for motion involves exerting pressure on the P6 pressure point -- the so-called nausea-relief point. Travelers can try pressing on the nausea-relief point, located two finger widths below the crease of the wrist on the palm-up side and between the two major tendons leading to the hand. Studies have been inconsistent on the benefits of wrist bands. Some studies have reported relief with a wristband (such as ReliefBand) that uses batteries. These batteries create a small electric charge at the acupressure point. The device may cause a rash, and people with pacemakers should not use it.
- Cold packs. In one study, applying cold packs to the forehead reduced the stomach activity of motion sickness.
- Eating small meals. Protein meals may be more effective in controlling stomach activity than carbohydrates.
- Behavioral Techniques. Some studies have reported relief by using certain behavioral approaches such as controlled breathing (concentrating on breathing gently or deeply), or listening to music.
Issues Involving Air Travel
Effects on Circulation. Traveling by car, airplane, or train for more than four hours increases the risk for blood clots in the legs (deep vein thrombosis, also known as DVT) in anyone. Those at highest risk include people with cardiovascular disease or its risk factors, people who have had recent surgery, cancer patients, and those taking oral contraceptives. Studies now suggest that DVT is the cause of more deaths than previously believed, because symptoms typically occur days after travel. In order to keep circulation moving during international flights or on trains, travelers should drink plenty of fluids, avoid salt, wear slippers, wear clothing that fits loosely in the waist and legs, take frequent walks in the aisles, and lift their legs up and down several times an hour. Two 2003 studies suggested that special stocking that compress the calves and ankles (such as Kendall Travel Socks, Sigvaris Traveno) may significantly prevent swelling and possibly blood clots due to long flights, even in travelers at medium to low risk.
Respiratory Infections. Flight cabins have very low humidity, which not only increases the risk for dehydration and dry eyes, but it also increases the risk for triggering disease in the airways. Fliers with colds or allergies are especially susceptible. The first rule is to drink plenty of liquids. Taking a decongestant tablet or nasal spray (not one containing an antihistamine) 30 minutes before flight can help prevent sinus and ear infections.
Of greater concern are studies suggesting that the prolonged time (8 hours or more) spent in the confined space of an airplane, combined with the close proximity to passengers from around the world, may facilitate the spread of serious contagious diseases such as tuberculosis. The CDC and World Health Organization now have guidelines on when and how to determine the need for preventive treatments after possible exposure to infectious organisms. (Recirculated air, which is now common in new aircraft, does not increase the risk for respiratory infections.)
Preventing Jet Lag. Crossing time zones can throw off the body's natural rhythms, especially when travelers fly from west to east. But jet lag can be minimized. A few days before long flights, adjust sleeping and eating patterns:
- When traveling west, travelers might avoid outdoor light after 6 p.m.
- If traveling east, travelers might begin going to bed earlier a few days before the trip and avoid outdoor light until 10 a.m.
- If possible, flights should be completed well ahead of an important event requiring concentration.
- If crossing multiple time zones, the traveler should schedule overnight stopovers.
- The traveler should drink plenty of fluids, but avoid alcohol and coffee, which increase fluid loss.
Melatonin, a natural hormone associated with light changes, may help people recover from jet lag. Some people report good results by taking it on the day of departure a half hour before the expected sleeping time in the arrival city. Travelers might also ask their doctors about short-acting benzodiazepines ("sleeping pills") such as lorazepam (Ativan); benzodiazepine-receptor agonists such as zolpidem (Ambien) or eszopiclone (Lunesta); alprazolam (Xanax); or temazepam (Restoril). Note that these drugs have been known to cause short-term forgetfulness and other side effects, and should be tested out at home before traveling.
Reports of illnesses aboard cruise ships, particularly gastrointestinal problems from contaminated food, have alarmed many travelers. A sanitation program conducted by the U.S. Public Health Service should significantly cut the risk for such problems. Cruise ships are inspected twice a year and are then rated. The CDC provides ratings to the public for all ships sailing from U.S. ports. At this time the ratings are the only guide for a healthy cruise. Meanwhile, cruise-ship travelers should avoid eating eggs and shellfish to help protect against diarrhea.
Aside from sanitation, health problems in general are common on cruise ships. A study of one major cruise ship reported that nearly 30% of the passengers were treated for skin disorders and 26% for respiratory problems while on board. The highly contagious norovirus, brought on board by one passenger, can quickly spread throughout the ship. Flu outbreaks sometimes occur even in summer. Older people who have not been immunized the previous flu season should ask their doctor about flu vaccinations. They add no value for people who had been previously immunized.
Preventing Skin Disorders
An estimated 3 - 10% of travelers experience some skin problem related to their trip, particularly when traveling to tropical and subtropical areas.
Avoiding Excessive Exposure to Sunlight. Many developing countries are in the tropics, were sunlight is intense. Ultraviolet radiation from sunlight not only can cause sunburn, but excessive sunlight and heat can cause toxic skin reactions in susceptible individuals. Everyone should avoid episodes of excessive sun exposure, particularly during the hours of 10 a.m. to 4 p.m., when sunlight pours down 80% of its daily dose of damaging ultraviolet radiation. Reflective surfaces like water, sand, concrete, and white-painted areas should be avoided. Clouds and haze are not protective. High altitudes increase the risk for burning in shorter time, compared to sea level and lower altitudes. Sunscreens and sunblocks with an SPF of 15 or higher are important and should be used generously. However, they should not be relied on for complete protection. Wearing sun-protective clothing is equally important, and provides even better protection than sunscreens. Everyone, including children, should wear hats with wide brims.
Preventing Skin Infections. People who visit the tropics or developing regions are at risk for a number of skin disorders, including infections with fungi and other organisms. Cleanliness is essential. Bathing or showering is very beneficial, but if there are no facilities, simply washing with soap and water (even if cold) is still helpful. (Note: Taking multiple daily showers can remove protective oils and is not recommended.)
The skin should also be kept dry in order to prevent fungal infections, which thrive in damp, warm climates. Take special care to clean and keep dry certain skin areas where infections are most likely to occur. They include creases in the skin, the armpits, the groin, buttocks, and areas between the toes. Use talcum powder in these areas. Keep socks dry.
Precautions when Traveling to High Altitudes
Acute high altitude illness, or mountain sickness, can affect the brain (cerebral edema), the lungs (pulmonary edema), or both. Studies suggest that about 25% of mountain climbers experienced symptoms at 7,000 - 9,000 feet, and 42% of them have symptoms at 10,000 feet. Rapid ascension to high altitude, such as arrival by airplane, increases the risk. In most cases the condition is mild. Severe lack of oxygen at high altitudes, however, can cause serious problems in some people.
- Acute Mountain Sickness. This syndrome is defined as headache and at least one other relevant symptom when a person travels to about 8,000 feet. Other symptoms include upset stomach, dizziness, weakness, fatigue, and difficulty sleeping. It typically develops in the first 12 hours, and may resolve spontaneously if the traveler remains at the same altitude.
- High Altitude Cerebral Edema (HACE). HACE is a life-threatening brain swelling and the severe endpoint of acute mountain sickness. Symptoms include altered consciousness, loss of coordination, difficulty concentrating, and lethargy. In extreme cases, it can lead to coma and death.
- High Altitude Pulmonary Edema (HAPE). HAPE is the occurrence of fluid in the lungs, which in rare cases can be severe. In one study, about 75% of mountain climbers who ascended to 15,000 feet had some mild form of HAPE. Worse performance and a dry cough suggest the onset of HAPE. In extreme cases it can cause severe lung deterioration. (If it is going to develop at all, HAPE usually occurs in the first 2 days and rarely after 4 days at a given altitude.)
Luckily, symptoms of the more severe complications come on slowly, are easily recognized, and resolve when returning to a lower altitude.
Risk Factors for High Altitude Sickness. The risk for high altitude sickness is determined by certain characteristics: The rate at which a person ascends; the altitude reached; altitude during sleep; and individual physiology. People who live yearlong at low altitudes are much more likely to be ill at greater heights. Being physically stronger is not protective. Certain common conditions (heart disease, diabetes, hypertension, mild emphysema, and pregnancy) play no role in a person's risk for high altitude sickness. (Upper respiratory infections, however, do increase the risk for HAPE.)
Precautions against Mountain Sickness. Acclimatization by staying several days at increasingly higher altitudes is recommended. If you take high blood pressure medication, ask your doctor about increasing dosage if traveling to high altitudes. And anyone with a chronic medical condition should check with his or her doctor.
The following are some measures for preventing mountain sickness.
- As a rule, ascend no more than 1,000 feet per day at altitudes of 8,000 feet and above. Drink 6 - 8 glasses of water or juice a day and avoid alcohol.
- Stop climbing when experiencing any symptoms of acute mountain sickness. Descend if symptoms worsen. Also descend immediately if you have any symptoms of HACE or HAPE.
- Supplementary oxygen may be required for people who show signs of these conditions.
- People who are hiking to very high altitudes may consider an inflatable chamber (Gamow bag and others). Such devices enclose a person, and when pumped up they simulate air pressure found at low altitudes.
Medications Preventing and Managing Mountain Sickness. Some medications are available for prevention or treatment of acute mountain sickness.
- Ibuprofen (Advil) may be sufficient to manage headache associated with acute mountain sickness.
- Acetazolamide (Ak-Zol, Diamox) taken one day before, and continued during initial exposure to high altitude, can reduce symptoms of acute mountain sickness, improve exercise performance and sleep, and reduce muscle and body fat loss. It may be used to treat minor symptoms of acute mountain sickness, but if symptoms persist, the traveler should descend to a lower altitude.
- Dexamethasone (Decadron Phosphate, Dexasone, Hexadrol Phosphate) is used to treat acute mountain sickness and cerebral edema (HACE). Dexamethasone is not recommended for prevention, however, because of potentially dangerous side effects.
- Nifedipine (Adalat) is used to treat pulmonary edema (HAPE) and may be used for prevention in people who know they are at high risk for HAPE.
- Preventive use of salmeterol (Serevent), a long-acting inhaled asthma drug known as a beta-adrenergic agonist, may reduce the risk for HAPE by over 50%.
Precautions for Divers
Travelers planning to descend rather than ascend must also take precautions. Individuals with the following conditions should not scuba dive:
- Heart and lung diseases
- Bleeding disorders
- Chronic ear infections or sinus infections blocking the ears
- History of seizures
- History of migraine headaches
Diving, in fact, is becoming known as a cause of many types of headaches, and anyone with a history of chronic or frequent headaches should discuss these issues with a health professional familiar with this sport.
Avoiding Air Embolism. Air embolisms are bubbles that obstruct blood vessels and can occur in divers who hold their breath while swimming up to the surface. They can be life threatening and cause long-term neurologic impairment, including memory lapses, impaired thinking, and emotional disorders. Even tiny bubbles may do some harm over time. One study found that in amateur divers who dive frequently, tiny bubbles appeared to increase the risk for small brain lesions and degenerating spinal disks.
To eliminate these bubbles, experts recommend that you:
- Ascend no faster than 30 feet per minute
- Remain 15 feet below the surface for 3 - 5 minutes before surfacing
- Avoid air travel for 24 hours after diving.
Drowning. The other major cause of scuba diving deaths is drowning in underwater caves due to improper training and poor equipment.