While Ebola virus disease (EVD) is on everyone’s mind, ill travelers returning from West Africa are far more likely to have malaria, according to findings from the GeoSentinel Surveillance Network.

“We need to keep common diseases in mind in travelers returning from Guinea, Liberia, and Sierra Leone,” Dr. Davidson H. Hamer, from Boston University in Massachusetts, told Reuters Health by email. “These include malaria, acute diarrhea, and influenza, and other febrile respiratory tract infections. In addition, there is a broad array of other infections that can cause symptoms and signs that overlap with Ebola, including typhoid fever, nontyphoidal salmonellosis, dengue, and many other less common illnesses.”

Fears surrounding the EVD epidemic have sometimes resulted in delayed evaluation and management of non-Ebola-related febrile illnesses among travelers arriving from West Africa, prompting Dr. Hamer and colleagues to provide an evidence base to inform the differential diagnosis of sick travelers from the Ebola epidemic region and improve evaluation and medical management.

They used data from GeoSentinel, a network of 57 specialized travel and tropical medicine clinics on six continents. The database for 2009–2014 included 805 individuals with confirmed or probable diagnoses attributable to travel in Sierra Leone, Liberia, or Guinea.
Systemic febrile illness was the most common syndrome classification (49.2%), followed by acute diarrhea (19.6%), other gastrointestinal symptoms (11.7%), and respiratory illness (6.7%), according to the May 12 Annals of Internal Medicine online report.

The most frequent diagnoses among non-immigrant travelers were malaria (40.3%), acute diarrhea (12.3%), influenza-like illness or upper respiratory tract infection (4.2%), viral syndrome (3.8%), and febrile illness not otherwise specified lasting less than three weeks (3.1%).

Among immigrants from these regions, the most common diagnoses were latent tuberculosis (42.9%), dental caries (31.4%), schistosomiasis (31.4%), strongyloidiasis (17.1%), and giardiasis (14.3%).

Malaria was also the most common diagnosis among children (40.3%), followed by giardiasis, anemia, cutaneous fungal infection, and upper respiratory tract infection.
Only 39% of returning travelers with malaria had received pretravel counseling, the researchers noted.

“Where adequate laboratory capacity exists, ruling out malaria in febrile travelers from West Africa is critical to limiting morbidity and mortality,” they wrote. “In situations where laboratory infrastructure is inadequate or a diagnostic result will be delayed, administration of empirical antimalarial therapy and broad-spectrum antibiotic coverage for bacteremia is imperative and potentially life-saving.”

The authors added, “Patients with a confirmed diagnosis of malaria who are still considered at risk for EVD may continue to require isolation precautions until EVD is excluded. However, those with malaria who improve clinically and defervesce during antimalarial treatment and who do not have signs of concomitant EVD (such as large-volume diarrhea), even if they are at risk for EVD, may come out of isolation unless their clinical status changes within the 21-day Ebola virus incubation period.”

“We need to remind physicians and other health care providers to take a travel history,” Dr. Hamer concluded. “If you do not know that a patient has been in West Africa, then malaria and EVD might be missed altogether.”

Dr. Justin Stoler, from the University of Miami’s Department of Geography and Regional Studies, Coral Gables, Florida, told Reuters Health by email, “Given increased air travel and accelerating globalization, clinicians, now more than ever, need to keep their epidemiological knowledge current. A physician might reasonably suspect malaria in any febrile patient who traveled to any rural area in sub-Saharan Africa without the use of malaria prophylaxis. Given the various incubation periods and non-specific symptoms of most tropical febrile illnesses, and higher probability of severe disease, this report underscores the need for innovation and widespread use of point-of-care diagnostics for tropical medicine.”

“Communicable diseases are geographically diverse and very poorly understood in sub-Saharan Africa,” Dr. Stoler said. “This report offers a glimpse of the complexity of tropical medicine in West Africa (and more broadly, sub-Saharan Africa). Recent seroprevalence studies from other sub-Saharan African nations yield different mixes of infections, as local immunology and exposures vary greatly from those of non-immigrant travelers. EVD is yet another reminder of how little we know about infectious disease epidemiology in Africa.”

This research was supported primarily by the U.S. Centers for Disease Control and Prevention, which supports GeoSentinel Surveillance Network, along with the International Society of Travel Medicine. Dr. Hamer reported being principal investigator for GeoSentinel and owning equity in Alere, a company that produces a rapid malaria diagnosis test; coauthor Dr. Castelli reported receiving research support from GeoSentinel and being an investigator in a clinical trial of a malaria drug for Sigma Tau.