Emerging Infectious Diseases: Is There Cause for Concern?

Thanks in large part to the ease and frequency of international travel, the U.S. has seen the emergence of several "new" infectious diseases, like Chikungunya and Ebola, which were previously seen only in other parts of the world. But not all emerging health problems originate in exotic locales, nor are they necessarily a major concern in this country.

An infectious disease can be caused by viruses, bacteria, fungi or parasites and, in some cases, can be transmitted from insects and other animals to humans. Measles, chicken pox, turberculosis, malaria, and seasonal flus are all familiar examples of infectious diseases that can be dangerous and potentially life-threatening, especially to young children, the elderly, and anyone with a compromised immune system. For most of us, however, the availability of vaccines and other appropriate healthcare have eliminated or greatly reduced the risk.

Chikungunya Virus

Once confined to Africa and Asia, this mosquito-borne virus has infected millions of people around the world since it began to spread through Europe in 2004. The virus was first identified in the western hemisphere on the Caribbean island of St. Martin in 2013. By January 13, 2015, there were 2,344 confirmed cases of chikungunya in the U.S., according to the Centers for Disease Control and Prevention (CDC). All but eleven in occurred in individuals who had travelled to areas where the virus had previously been reported; the remaining locally-transmitted cases were reported from Florida. The CDC expects increased reports among travellers, which could contribute to an increase in locally transmitted cases.

Chikungunya Symptoms and Prevention

The most common symptoms of chikungunya infection are fever and joint pain but may also include muscle pain, joint swelling, and skin rash. Luckily, "Infection is rarely fatal," assures infectious disease specialist Catherine Passaretti, MD, of Carolinas HealthCare System in Charlotte, NC. "But joint symptoms can persist for months."

The best way to prevent infection is to avoid mosquito bites by using insect repellents and wearing long sleeves and long pants. The mosquitos that carry the chikungunya virus are mostly active during the day and can dwell by standing water.


As far back as 1976, serious outbreaks of Ebola virus have occurred in several African countries, where the virus was first discovered and is thought to have originated in native bats.

There are five identified strains of Ebola virus, four of which can infect humans. The current outbreak, involving more than 20,000 patients in West Africa, is the largest in history. It has been relatively contained to Liberia, Sierra Leone, and Guinea.

As of January 16, 2015, the CDC notes that only four cases of Ebola have been diagnosed in the U.S.: three healthcare workers who had been in contact with an Ebola patients and who survived, and one individual who visited the U.S. from Liberia already in a late stage of the disease and died within a week.

Ebola Symptoms and Prevention

Ebola is characterized by stomach pain, diarrhea, vomiting, fever, headache, body aches, and unexplained bleeding or bruising; symptoms typically appear seven to 10 days after exposure but can appear up to 21 days after exposure. Note that "A patient infected with Ebola cannot transmit infection until they become symptomatic," Passaretti points out. "Transmission occurs via exposure to blood or bodily fluids such as stool or vomit, putting healthcare workers and other very close contacts at highest risk of infection."

The CDC advises travellers to areas affected by an Ebola outbreak to be vigilant about hygiene: wash your hand thoroughly, and avoid contact with the blood, body fluids, and personal items of infected people; also steer clear of bats and nonhuman primates. Healthcare workers should follow stricter protocols to avoid infection.

Enterovirus EV-D68

There are many enteroviruses; one of them, rhinovirus, causes the common cold. Enteroviruses tend to circulate during the summer and fall months. In the summer and fall of 2014, however, CDC scientists identified much higher-than-typical numbers of infections caused by a severe enterovirus called EV-D68.

EV-D68 Symptoms and Prevention

EV-D68 most frequently causes low-grade fever, runny nose, and cough in children and teenagers. Symptoms tend to go away without treatment, just like a typical cold. However, in a small subset of patients, most typically children with asthma, EV-D68 can cause severe difficulty breathing and may require hospitalization.

The increased cases of EV-D68 in 2014 were first identified in Missouri and Illinois before spreading to other states; between mid-August 2014 and mid-January 2015, there were a total of 1,153 confirmed cases in 49 states. The CDC is still investigating a possible link between EV-D68 and cases of acute limb weakness and spinal cord lesions. It remains unclear if these cases were actually related to EV-D68 infection.

"The best way to prevent transmission of all cold viruses, including EV-D68, is to ensure children wash their hands frequently with soap and water, cover mouths while coughing and sneezing, avoid other children who are ill, and to regularly clean surfaces children touch, such as tabletops and toys," advises Passaretti.

Catherine Passaretti, MD, reviewed this article.


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