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New and emerging diseases

Microbial disease agents are constantly evolving. And that is ever more the case in the 21st century, given the ubiquity of global travel and thus the ease with which microbes can now spread. Before the 2014 Ebola outbreak in West Africa, for example, few people outside the infectious diseases community had ever heard of the deadly hemorrhagic fever — then suddenly it was all over the media. So today's up-to-the-minute knowledge may be tomorrow's old news. But at least as of the writing of this guide, the following diseases were among those relatively new on the traveler's radar.Microbial disease agents are constantly evolving. And that is ever more the case in the 21st century, given the ubiquity of global travel and thus the ease with which microbes can now spread. Before the 2014 Ebola outbreak in West Africa, for example, few people outside the infectious diseases community had ever heard of the deadly hemorrhagic fever — then suddenly it was all over the media. So today's up-to-the-minute knowledge may be tomorrow's old news. But at least as of the writing of this guide, the following diseases were among those relatively new on the traveler's radar. Avian influenza, also known as bird flu, is a disease primarily in birds that's caused by influenza A viruses. It is present in over 100 bird species worldwide. The primary hosts for avian influenza A are aquatic birds — such as gulls, terns, and shorebirds — and waterfowl — such as ducks, geese, and swans; avian influenza A can also infect domestic poultry and some other animals. The risk to humans is low, but there have been some cases of human infection in some Asian countries. Travelers to that region should avoid contact with wild birds, with dead or sick-looking domestic birds, and with surfaces or objects contaminated with droppings from ill birds.Chagas, also known as American trypanosomiasis, is a dangerous disease caused by the parasite Trypanosome cruzi. This protozoan is typically transmitted to animals (including humans) by insect vectors found only in rural areas of the Americas, from the southern states of the U.S. to the northern provinces of Argentina. The typical vector is an insect often referred to as the kissing bug, a triatomine bug, but its common name varies from country to country. Triatomines are gregarious; typically, they take refuge during the day in dark, cool crevices and come out at night. These blood-sucking insects are guided to their prey by odor, heat and carbon dioxide. In some areas, their behavior seems to be changing, however, and they are seen during daylight hours as well. Recent studies suggest that bedbugs may also be a vector for the Chagas parasite. It can also be transmitted via blood transfusions (including organ transplants) or foods contaminated with an infected bug's feces, as well as congenitally (from mother to fetus) or by lactation (from mother to nursing baby). The parasite's usual reservoir in nature is opossums, raccoons, armadillos and small rodents, but domestic animals like cats and dogs are also known to harbor the parasite.

The kissing bug bites and defecates at the same time. It is the subsequent scratching at the site of the bite that allows the parasite to enter the host though the tiny bite wound. The bite site usually does not show any significant inflammatory process and is not painful. The acute phase of the infection (which lasts for a few weeks to a few months) may pass unnoticed because symptoms are typically nonexistent or mild, vague, and unspecific. The chronic phase develops over the course of several years. Between 60 and 80 percent of individuals with chronic Chagas never develop any other symptoms (this is known as indeterminate Chagas), while the remaining 20 to 40 percent may develop cardiac and/or digestive complications that can be life-threatening.

There are no vaccines against Chagas disease and current treatment options are largely ineffective. As a result, travelers should focus on avoiding contact with the kissing bug. Unfortunately, they have become resistant in some areas to first-line repellents and insecticides like DEET and permethrin. Mechanical barriers, such as mosquito nets and screens, can be effective, but avoiding sleeping outdoors, at hostels, and in mud houses in endemic areas is the best way to prevent contact with Chagas vectors. This, too, is a mosquito-borne infection — a viral illness with an incubation period of several days. It causes fever, significant joint pain, and sometimes a rash or headache. "Chikungunya" means "that which bends up" in a language spoken in Tanzania; the pain from the disease can be severe enough to cause those afflicted to bend forward. It is of note to divers that the bent-over gait and joint pain of chikungunya can be confused with the symptoms of decompression sickness, also known as "the bends," for it, too, causes sufferers to assume a bent position due to pain. Chikungunya has spread from Africa and Asia to the Caribbean.

There is no vaccine against chikungunya and no known treatment other than rest and good hydration, so preventive measures targeted at avoiding mosquito bites, particularly between dusk and dawn, are strongly advised. This means staying in well-screened areas when you're indoors, wearing clothes that cover most of your body when you're outdoors, and using mosquito nets when you're sleeping. You should also use insecticides and repellents on your clothing, tents and nets, as well as personal repellents containing at least 30 percent DEET (note that concentrations above 30 percent do not add significantly to its protective effect or duration). Standard preparations last about four hours; longer-acting preparations are available. Picaridin is an effective alternative.Dengue is a viral disease transmitted by the mosquito Aedes aegypti. It has a sudden onset, with symptoms including fever, severe frontal headache, and joint and muscle pain; nausea, vomiting and a rash may also occur. The disease is usually self-limited and benign, but it may require a long convalescence. Dengue fever can also occur in a severe, fatal form called dengue hemorrhagic fever.

Dengue is found in tropical and subtropical climes worldwide, mostly in urban and semiurban areas. The global incidence of dengue has grown dramatically in recent decades. According to the U.S. Centers for Disease Control and Prevention (CDC), about 100 million cases of dengue fever and several hundred thousand cases of the hemorrhagic form of the disease are reported every year. About half of the world's population is now at risk. Severe dengue causes over 20,000 deaths every year and is a leading cause of serious illness and death among children in some Asian and Latin American countries.

In the recent years, dengue outbreaks have occurred in the Caribbean and Central America. Areas with widespread dengue include the South Pacific, Southeast Asia, India and the Middle East. The distribution of dengue fever is similar to that of malaria and yellow fever.

There is no vaccine available and no known treatment other than rest and good hydration, so preventive measures targeted at avoiding mosquito bites, particularly between dusk and dawn, are strongly advised. This means staying in well-screened areas when you're indoors, wearing clothes that cover most of your body when you're outdoors, and using mosquito nets when you're sleeping. You should also use insecticides and repellents on your clothing, tents and nets, as well as personal repellents containing at least 30 percent DEET (note that concentrations above 30 percent do not add significantly to its protective effect or duration). Standard preparations last about four hours; longer-acting preparations are available. Picaridin is an effective alternative.Ebola is a rare and deadly hemorrhagic viral illness. It affects humans, as well as monkeys, gorillas, and chimpanzees. There are at least five identified Ebolavirus species that have been found in several African nations; bats are their most likely reservoir. Ebola was first discovered in 1976 near the Ebola River in what is now the Democratic Republic of the Congo. In succeeding decades, relatively small outbreaks appeared sporadically in Africa. Now, modern travel may be helping to disseminate the disease to other countries. A 2014 outbreak in West Africa resulted in more than 27,000 cases and 11,000 deaths — most of them within West Africa, but a few in other countries. Protection against Ebola's spread includes controlling traffic and screening air passengers coming from affected regions.

Ebola is acquired through direct contact with an infected individual — via broken skin or the mucous membranes in, for example, the eyes, nose, or mouth — or through contact with the blood or other body fluids of an infected person, with a contaminated object, or with fruit infected by bats or primates.

Its symptoms include fever, severe headache, muscle pain, weakness, fatigue, diarrhea, vomiting, abdominal pain and unexplained hemorrhaging (bleeding or bruising). Symptoms may appear anywhere from two to 21 days after exposure to the Ebolavirus. There is no vaccine or medication effective against Ebola. Current treatment options include supportive care — that is, measures to address symptoms as they arise — and the patient's own immune system.

If you must travel to a country affected by Ebola, current, detailed information can be found on the CDC website at Travelers' Health–Ebola .Hand, foot and mouth disease (HFMD) is a common viral illness that usually affects infants and children younger than 5 years old, though it sometimes affects adults. Outbreaks of HFMD occur from time to time in all parts of the world, including the United States. Japan, for example, reported over a quarter of a million cases in the first eight months of 2015.

The typical course of HFMD starts with a fever, reduced appetite, sore throat, and malaise (a feeling of being unwell), followed in a day or two by painful sores in the mouth. A skin rash with red spots, and sometimes with blisters, may also develop on the palms of the hands, the soles of the feet, the knees and elbows, and/or the buttocks and genital area. In rare cases, patients can develop meningitis (an inflammation of the membrane around the brain) or encephalitis (an inflammation of the brain).

HFMD is caused by various Enteroviruses present in the population worldwide. Transmission is from person to person via the excretions of infected individuals, who may not necessarily appear obviously ill. The virus is spread through close personal contact with someone who's infected, the air (coughing or sneezing by an infected individual), or direct contact with infected excretions or contaminated surfaces like doorknobs. There is no vaccine and no specific treatment other than symptom relief. Frequent hand-washing and not touching your eyes and mouth can mitigate the risk of infection. MERS stands for Middle East respiratory syndrome. It is a serious illness caused by a Coronavirus . It was first reported in Saudi Arabia in 2012 and affects the respiratory system. Symptoms include fever, cough and shortness of breath. The mortality rate is very high (between 30 and 40 percent). It is spread from person to person through close contact in hospital settings. So far, it has not spread into communities beyond hospital walls. The disease has, however, spread from the Middle East to Asia. And in 2014, two cases were reported in the United States — both in health-care workers who had recently returned from working in hospitals in an affected country. There is no vaccine against MERS. Current information on the disease can be found on the CDC website on the MERS FAQs page.SARS stands for severe acute respiratory syndrome. It was the first emergent transmissible disease of the 21st century. Like MERS, it is a respiratory illness caused by a virus Coronavirus . SARS was initially reported in Asia in February 2003, and it spread to more than two dozen countries in North America, South America, Europe, and Asia before the outbreak was contained in July of the same year.

More than 95 percent of the cases of SARS have occurred in the Western Pacific region. Globally, there have been more than 8,000 reported cases, resulting in over 770 deaths. As of late 2015, the most recent outbreak was in China in 2004. Nevertheless, the CDC and other agencies remain alert to the possibility of a renewed outbreak in humans; updates on new cases will be posted on the CDC's SARS page.The Zika virus is related to the viruses that cause dengue fever, yellow fever, Japanese encephalitis and West Nile fever. It is transmitted to people primarily through the bite of infected mosquitoes. Its symptoms include mild fever, a skin rash, muscle and joint aches and red eyes. Zika fever has been known since the 1950s as an endemic disease limited to the equatorial region from Africa to Asia. But since 2007, the virus has been spreading eastward. In 2015-16, it reached the Americas, causing Zika fever outbreaks of pandemic proportions. While symptoms in most cases of Zika infection are mild, or even nonexistent, infection during pregnancy may cause microcephaly (an abnormally small head) in some babies. In addition, a rare neurological complication known as Guillain-Barré syndrome may occur in a small proportion of adults. The Zika virus can be transmitted to humans by at least eight different species of mosquitoes of the Aedes genus. Mosquitoes become infected by biting infected animals or humans. Aedes mosquitoes are active mainly during the day. The best way to avoid mosquito bites in endemic areas is to wear long sleeves, use insecticides or insect repellents and stay in air-conditioned spaces. Also, after your return home from any area where the Zika virus is endemic, it is important to continue these mosquito-bite–prevention practices for two weeks, to avoid spreading Zika where you live. In addition, remember that Zika can be transmited by sexual intercourse as well. The Zika virus has been found in semen up to two months after infection, so proper protection during sex is recommended.


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