Ebola poses less of a risk to Americans than more contagious infections headed this way
Published: August 19, 2014
Health preparedness and procedures in the United States should prevent a domestic outbreak of Ebola, whose death toll in western Africa now has topped 1,000.
But a University of Pittsburgh virologist warns that the nation should focus on its vulnerability to other foreign viruses that are less deadly but far more contagious than Ebola, with a potential impact similar to seasonal influenza.
Some already have arrived. Other viruses well established in Africa, the Middle East or Asia could show up on the next boat or plane and spread by airborne disease particles, mosquito bites or contact with humans or livestock.
Yes, the African Ebola outbreak should generate international concern with a death rate as high as 90 percent of all cases.
“But I would also issue a word of caution that the public should have some perspective on this,” said Amy L. Hartman, an assistant professor at Pitt’s Graduate School of Public Health. “Even though this is the largest Ebola outbreak ever, there are other infectious diseases that cause millions of deaths per year — influenza, tuberculosis, dengue, malaria — but do not have the urban legend status of Ebola.”
But that level of concern and fear has led to development of a potential arsenal of antiviral weapons, including the drug favipiravir.
Ms. Hartman, who developed animal models to test the drug, said it’s undergoing final-stage human clinical trials before the U.S. Food and Drug Administration can approve it for human use. So far, the drug has been highly effective against the flu and better than current medications such as Tamiflu. But there’s also growing evidence of effectiveness against Ebola and many other viral infections.
“Favipiravir could have an impact on other viruses including West Nile,” Ms. Hartman said.
While there are no FDA-approved vaccines for Ebola, the National Institute of Allergy and Infectious Diseases is working to develop one. Efforts are underway to expedite a first-phase safety trial on an Ebola vaccine this fall, while supporting development of an Ebola/?Marburg virus vaccine by Crucell, and Ebola vaccine by Profectus Bioscience. The National Institutes of Health and the Thomas Jefferson University in Philadelphia are collaborating on an Ebola vaccine based on an already established rabies vaccine, the CDC reports.
Zmapp, an experimental Ebola treatment, has yet to be tested for safety but is available for compassionate use in Liberia in an attempt to bring the epidemic under control. The CDC said it’s too early to tell if the drug is effective. The FDA issued a warning last week about products being sold online that claim to prevent or treat the Ebola virus, ever since the outbreak in Africa occurred.
What some believe to be exaggerated fears of an Ebola outbreak in the United States are bolstered by the World Health Organization’s description of it as “one of the world’s most virulent diseases.” It also can be spread by direct contact with an infected person. The viral hemorrhagic disease causes fever, headache, joint and muscle aches, weakness, diarrhea, vomiting, stomach pain, lack of appetite and abnormal bleeding, the CDC says. Most common symptoms appear eight to 10 days after exposure.
But control is possible because a person must have symptoms to be contagious. The United States also has a strict protocol in place to monitor sick patients en route to the United States and isolate those with the disease in biomedical containment centers to prevent the virus from spreading.
“Whenever airline officials determine that a sick patient is aboard a plane destined for the United States, the CDC is notified to investigate whether the ill travelers might require isolation and assure the plane is disinfected. Such procedures were initiated during the 2003 outbreak of severe acute respiratory syndrome, or SARS, in Asia that eventually infected 8,273 people, including 27 cases in the United States, but none of whom was among the 775 deaths.
Annual health problems of influenza reflect the potential impact Americans might face if chikungunya, Rift Valley fever virus and Middle East Respiratory Syndrome (MERS), among many others, arrive in coming months or years. The CDC estimates that seasonal flu infects 5 percent to 20 percent of the U.S. population (as high as 64 million people) with more than 200,000 people hospitalized for flu-related complications annually.
“Over a period of 30 years, between 1976 and 2006, estimates of [annual] flu-associated deaths in the United States range from a low of about 3,000 to a high of about 49,000 people,” the CDC says.
As with the flu, some foreign viruses also can infect and kill livestock, birds and other animals, expanding the economic toll and making control even more difficult.
For now, chikungunya is well established in Caribbean and northern South American nations along with four locally transmitted cases of the virus in Florida. There are about 600 more cases in the United States involving travelers to this country. The CDC reports 14 cases in Pennsylvania, 16 in Ohio and 13 in Maryland, all involving travelers from elsewhere.
The Pan American Health Organization reported Aug. 1 that 31 countries and territories in the Americas have had locally transmitted cases of chikungunya [CHIK-en-GUN-ye]. There have been a total of 508,122 suspected cases reported and more than 5,100 confirmed as being locally transmitted and a total of 32 deaths from the virus in the Americas. Because chikungunya is new to the Western Hemisphere, most people are not immune. This means it can be more easily spread with the help of other types of mosquitoes.
The most common symptoms of chikungunya virus infection are fever and joint pain, the CDC states, along with headache, muscle pain, joint swelling or rash. The joint pain can continue indefinitely and even become chronic.
“With the recent outbreaks in the Caribbean and the Pacific, the number of chikungunya cases among travelers visiting or returning to the United States from affected areas will continue to increase,” the CDC states. “These imported cases could result in local spread of the virus in the continental United States.” The mosquitoes that transmit chikungunya are found throughout much of the Americas, but limited in this country mostly to Southern states.
Ms. Hartman has been working on the Rift Valley fever in a biocontainment unit at Pitt where she wears protective clothing resembling a moon suit to prevent contracting the virus and potentially spreading the disease.
The Rift Valley fever was first discovered in Kenya more than a century ago and spread by mosquitoes mostly through livestock. It continues to be of concern throughout Africa and into the Middle East, but the CDC says the virus, should it arrive in the United States, could infect livestock and have a major economic impact on agriculture.
MERS has been concentrated in Saudi Arabia with two travelers to the United States confirmed to have the severe viral respiratory infection that causes death in 30 percent of the patients. Symptoms include fever, cough and shortness of breath. The virus is spread through close contact with no evidence “of it spreading in community settings,” the CDC states.
The West Nile Virus provides an example of the impact when a virus arrives from overseas. First discovered in the United States in the late 1990s, it peaked in 2002 and 2003 with the CDC documenting 13,088 total cases between 1999 and 2012 and 1,549 deaths. The CDC and health agencies continue tracking infections every summer.
But there’s good news on the prevention and treatment front. Ms. Hartman, who holds a Ph.D. in virology, has been working with MediVector Inc. on development and testing of the drug favipiravir as a flu treatment that also has potential to treat such viruses as Ebola, Marburg, West Nile, Rift Valley, yellow fever, dengue and even hepatitis C. Her research included developing animal models on which to test the drug.
Favipiravir “is a novel anti-viral compound that works against different viral enzyme targets than either of the approved antiviral agents used to treat people who have become ill with influenza,” the MediVector website states, adding that scientists around the world “have tested favipiravir and found that it is effective against a wide variety of RNA viruses, in infected cells, infected animals, and both.”
In the meantime, other researchers are working quickly to develop other methods to prevent or treat such infections with a focus on Ebola.
Ronald N. Harty, associate professor of microbiology at the University of Pennsylvania School of Veterinary Medicine, is leading research to block certain RNA viruses from successfully completing replication and “budding,” which is the viral process of leaving the cell by expanding through the cell membrane much the way a bubble is created from a wand.
“We’re focused primarily on Ebola but also related RNA viruses,” said Mr. Harty, who also holds a Ph.D. in virology. He is co-founder of the company, Intervir, which will use the research to develop antiviral medications based on research that targets proteins and protein strands necessary for virus replication. “I’m very excited with good, promising data and tested inhibitors against live viruses in the lab. We’ve tested it against live Ebola and Marburg viruses that actually block budding.”