Global economy translates to emerging global infections

August 1, 2005

Chicago — The globalization of business, international adoption, immigration and tourism has given rise to the spread of new and emerging pathogens.

The phenomenon holds important implications for dermatologists since many infections are first seen in the outpatient setting.

"Diseases that were previously seen as exotic are now commonly seen in the U.S.," says Dirk M. Elston, M.D., of the departments of dermatology and pathology at Geisinger Medical Center, Danville, Pa. "New infections arising in rural China or Africa may arrive on U.S. shores within a single season. This creates a very hot topic for dermatologists-it means that they need to stay abreast of all the new pathogens, symptoms and treatments."

Bacterial infections

Antibiotic resistance among staphylococcal isolates is a growing problem in many regions of the country.

To compound the problem, community acquired methicillin-resistant staphylococcus aureus (CA-MRSA) is on the rise and is mainly associated with skin and soft tissue infections -cutaneous abscesses and cellulites are particularly common.

An oxazolidinone antibiotic called Linezolid (Pharmacia), is useful in treating skin and soft tissue infections caused by MRSA. The drug is generally well tolerated, and appears to be superior to vancomycin. However, because the drug is expensive and some resistance to it is already developing, many clinicians advocate its use only in cases where no suitable alternative is available, according to Dr. Elston.

Important pathogen

Another important emerging pathogen is vancomycin-intermediate S aureus. Phenotypic susceptibility to methicillin has recently been described, reinforcing the importance of culture and sensitivity testing in high-risk patients, as well as any infection that is unresponsive to initial therapy.

Other emerging - or re-emerging - infections include virulent toxin-producing strains of group A beta-hemolytic streptococci (leg infections are becoming more common); acinetobacter baumannii (which causes pneumonia, bacteremia, meningitis and urinary tract infections); and B. henselae infection. Most strongly associated with cats, this illness was recently reported in a police dog handler. In addition, the re-emergence of tuberculosis has special significance for dermatologists, since cutaneous manifestations will first be seen in their offices.

Rickettsial infections

By far, most of the cases of tick-borne rickettsiosis in international travelers are African tick bite fever caused by Rickettsia africae, and Mediterranean spotted fever caused by Rickettsia conorii.

Most affected travelers present with a flu-like illness and don't recall getting bitten by a tick. Nonetheless, the attack rate is substantial: A study of 940 travelers to rural Africa showed that 4 percent developed African tick bite fever. More than 26 percent had flu symptoms, and more than 80 percent had fever, headache and/or myalgia. Cutaneous signs such as eschars, lymphadenitis or rash were present in fewer than 50 percent of the patients. Both diseases respond to doxycycline.

Other emerging infections within the rickettsial category include human anaplasmosis (HA, formerly called human granulocytic ehrlichiosis), which is caused by anaplasma phagocytophilum, and human monocytic ehrlichiosis (HME), caused by Ehrlichia chaffeensis. Both are tick-borne infections. Patients will likely present with fever and various other symptoms including headache, myalgia and thrombocytopenia.

Viral infections

The outbreak of SARS in rural China and its worldwide spread in a single season demonstrated the vulnerability of the world population to the spread of new diseases.

Still, other viral infections have continued to emerge and threaten the world's population. In 1999, the people of New York City first heard about an asymptomatic infection known as West Nile virus, which is transmitted by Culex mosquitoes. By 2002, 4,156 human cases of infection had been reported resulting in 284 fatalities.