About half of the 153 volunteers in the study visited a doctor or hospital during their stay. In comparison, only about eight to 10 percent of tourists in South America, Africa and Asia seek local medical attention, according to past research.
"The problem is that these young people go to countries and experience cultures and they do not have the best information on what is going on around them," Dr. Thomas Küpper told Reuters Health.
Küpper led the current study based out of the Institute of Occupational and Social Medicine at RWTH Aachen University in Germany. He and his team wanted to know which health problems younger volunteers face and possible reasons why.
They sent questionnaires to young people who had attended a training course run by a German nongovernmental organization (NGO) before volunteering. The participants, aged 18 to 30, spent at least six months - and an average of 11 - in a developing country between 2001 and 2006.
About 20 percent of the volunteers originally contacted returned the questionnaire.
The top five ailments they reported included sunburns, diarrhea with no fever, self-treated injuries, headaches and stomach pain. Roughly 21 percent of the volunteers suffered dental pain and eight percent reported malaria symptoms.
Most of the volunteers stayed in Latin American countries, where malaria is less of a concern than in Africa. Just two percent of volunteers in Latin America and no volunteers in Asia got malaria, compared to 41 percent of people who went to Africa.
"The most important message is that these volunteers need to be prepared," said Dr. Atti-La Dahlgren.
"They are basically coming out of high school and have little or no experience being abroad in developing countries," he told Reuters Health.
Dahlgren has researched travel abroad in his work at Geneva University Hospitals' Division of International and Humanitarian Medicine in Switzerland. He was not involved with the current study.
Preparation is all the more important because "it is an increasing and positive phenomenon that young people want to have experience doing work in developing countries," he said.
"What worries me a bit is that it seems like only about half of respondents who went to Africa received correct information about the risks and treatment of malaria," Dahlgren said.
The researchers write in the journal Travel Medicine and Infectious Disease that malaria prevention advice before trips was "simply chaotic." Some volunteers were told to take pills that prevent the disease for one week only. Others going to low-risk areas were advised to take them long-term even though it was not necessary.
Dahlgren said such conflicting information was alarming. "We know which areas are dangerous and we know how to prevent malaria," he said.
According to the survey, 56 percent of volunteers received pre-travel advice from their family doctor.
The study reinforces the importance of getting information from doctors specializing in travel abroad medicine, said Dr. Poh Lian Lim of Tan Tock Seng Hospital in Singapore. She has researched the subject but was not part of the current study.
"The average family doctor may not know the ins and outs of being in a place like Ecuador," Lim said.
Once volunteers are abroad, they also need to use caution within their local communities, she added.
"One of the more worrisome parts of the study is that 20 percent of the volunteers relied on local healers for treatment," Lim said. "Seeing a local healer for a tension headache might be okay, but for headache caused by meningitis or malaria, then that's not okay."
"People who volunteer may look at this study and think, ‘Well, most of these things I can take care of myself,' but the situations could have turned out badly," Lim told Reuters Health.
She added that self-reported health questionnaires can miss valuable details that doctors would provide.
"Within the category of headaches, we don't know if these were caused by a flu-like illness, or something else, like dengue fever," Lim said.
Küpper and his team recommend that all NGO volunteers attend mandatory health sessions given by trained doctors with simple, clear messages. Volunteers traveling to areas like Western Africa, with high rates of malaria, should receive specific medical training.
Dahlgren pointed out that the study looked at a period in which smartphones and Internet connections were less common than they are now.
"It is much easier to stay in touch with your home base now and get adequate medical information," Dahlgren said. "Volunteers could even show, via Skype, their injuries or illnesses to doctors back home."
"With smartphones, you could also have improved medicine compliance. For example with malaria, volunteers could receive an SMS (text) message every day reminding them to take their pill," he said.
Küpper and Lim agreed on the single most important medical tool for volunteers: their minds.
"Volunteers must look at the situation where they are and ask, ‘Is this situation safe?'" Küpper said.