Emerging viruses such as Ebola, SARS and swine flu are familiar sounding, yet seemingly distant diseases to many Americans. But that's not the case with Chikungunya, a mosquito-borne virus that recently struck close to home and has proven deadly for the elderly.
In 2014, 12 cases of locally acquired Chikungunya were reported in Florida, and more than 4,000 were reported in Puerto Rico, the U.S. Virgin Islands and American Samoa. The virus is not often deadly, but of the cases that are, more than 90 percent occur in individuals 65 and older or in people with weakened immune systems.
"We dodged a bullet," said Janko Nikolich--ugich, MD, PhD, professor and chair of the Department of Immunobiology at the University of Arizona College of Medicine - Tucson.
The U.S. mosquito season waned just as those cases were reported, he explained.
"We were primed for an outbreak in 2015, but we didn't get it," said Dr. Nikolich--ugich, who is co-director of the UA Center on Aging and a member of the UA BIO5 Institute.
Now, using a $1.5 million federal grant from the National Institute on Aging, the internationally recognized immunologist will study how Chikungunya causes devastating effects in older adults to improve treatment options.
When an individual becomes infected, the virus causes arthritis-like symptoms, such as joint and muscle pain, swelling and rash. Symptoms can last months to years, and are particularly prolonged and severe in older adults. East Africans aptly named the virus "Chikungunya," meaning a crooked person unable to stand straight.
With no vaccine or treatment, individuals can recover only with bed rest, fluids and pain relievers, such as acetaminophen.
Chikungunya masquerades as arthritis, but can be far more destructive, said Dr. Nikolich--ugich, who is determined to help our nation be ready for the next U.S. outbreak.
"In the United States, more than 20 percent of the population is 65 or older," he said. "By 2050, one-third of the U.S. population will be over the age of 65, and, therefore, vulnerable."
Using his new grant, the immunologist will study an immune hormone called transforming growth factor beta (TGF?). His team has found that when older mice are infected with Chikungunya, their body secretes excessive amounts of the hormone. The hormone is effective at combatting certain infections, but is completely unequipped to fight off Chikungunya, Dr. Nikolich--ugich said.
"The virus is tricking the body to secrete TGF?, taking the immune system down the completely wrong rabbit hole," Dr. Janko Nikolich--ugich explained.
His UA lab has shown that blocking TGF? can reduce Chikungunya sickness in old mice. Now the lab will determine exactly how the hormone makes older individuals succumb to Chikungunya more easily - and how to block its effect on the elderly.
Chikungunya was discovered in the early 1950s in Africa and is endemic in areas throughout the Indian Ocean. In the last 20 years, it has migrated to the Middle East, Europe and the United States.
Between 2005 and 2006, 250,000 individuals were infected with Chikungunya on Réunion, an island off the southeastern coast of Africa. Of those, 213 died from the infection.
Dr. Nikolich--ugich cites Réunion as an example of what America's fate could be - but on a much smaller scale. He fears the United States will have a much higher mortality rate when Chikungunya strikes again because of its large elderly population. Only 6 percent of Réunion islanders were 65 or older.
The United States is home to two of the mosquitoes that carry the virus: aedes aegypti, also known as the yellow fever mosquito, and aedes albopictus, also called the Asian tiger mosquito. U.S. locations at risk for the virus include Florida, Texas and areas where it is hot and humid during mosquito season, from May through July.
"Dr. Nikolich--ugich is doing groundbreaking work for Chikungunya and other diseases that presently have no vaccine and no cure," said UA President Robert C. Robbins, MD. "This work is important not only because it can show us how to combat certain infections, but also because Dr. Nikolich--ugich and his team are anticipating a potentially serious outbreak in the future and looking to mitigate its effects. I am thrilled by what this grant will enable, and I look forward to the results of this study."