Why humans are making epidemics worse

Atlanta-Nearly every year there seems to be some new epidemic that crops up, creating healthcare crises and worldwide panic. Robert Kalayjian, MD, director of infectious diseases at MetroHealth Medical Center in Cleveland, says these epidemics are becoming more common, and he explained the implications for public health during a session at SECO 2016. 

Dr. Kalayjian says the way humans interact with the environment allows for emerging and reemerging infectious diseases such as Ebola and Zika to play out in similar patterns time and time again.

Related: How to diagnose Zika in your practice

How our environmental impact affects disease

Of the 18 Ebola outbreaks in equatorial Africa since 1975, most occurred in remote areas where extensive transmission from person to person was unlikely, says Dr. Kalayjian. The epidemics were relatively small and quickly contained. In total, fewer than 2,000 people were infected in those epidemics, and 1,296 people died.

The latest outbreak, however, occurred in densely populated cities in which the virus spread like wildfire. For comparison, the Centers for Disease Control and Prevention (CDC) estimates that more than 28,600 people were infected in Guinea, Sierra Leone, and Liberia during this epidemic, with more than 11,000 deaths. (Other countries, including the United States, experienced a total of 36 infections, including 15 deaths.)

“The first important principle I’d like to emphasize is that in all cases, we know that these epidemics occurred by interactions with infected animals-bats or primates-and it speaks to environmental degradation and human encroachment into the habitats of these animals that has allowed this to occur,” says Dr. Kalayjian.

About 60 percent of human infectious diseases are somehow related to wild and domestic animals, he says. Rabies, for example, is passed from a rabid animal to a human, but it is unlikely to be passed to other humans from there. Ebola is passed to humans through some interaction with either great apes or fruit bats, but then it is able to be transmitted from person to person.

Another factor that makes these epidemics hard to contain is the increasing ease with which humans travel. The most recent Ebola epidemic spread very easily among Guinea, Sierre Leone, and Liberia in part because of the very porous borders among the countries, says Dr. Kalayjian.

“Importantly, the epidemic could be tracked traveling along the transportation routes between very populous cities,” he says.

Climate change-not just increasing temperatures, but also changes in precipitation-is also affecting the spread of infectious diseases.

“Lyme, anaplasma, babesiosis, and ehrlichia are all transmitted by tick vectors,” says Dr. Kalayjain. “Climate change is playing a role in the population of those ticks and their ability to thrive in warm environments.” 

As such, Dr. Kalayjian says that a “One Health” approach is required to prevent and contain future outbreaks of infectious diseases. This approach requires collaboration among human, animal, and environmental health entities on disease surveillance, outbreak response, and prevention to achieve an optimal human health outcome. The One Health concept is supported by the CDC.

Next: Ebola

Ebola

While the most recent Ebola crisis in West Africa was declared over by the World Health Organization in January 2016, the organization warned there would continue to be flare-ups of the disease. That prediction was quickly fulfilled-Guinea reported at least five people have died of Ebola in March 2016, leading Liberia to close its boarder with Guinea to help prevent spread of the disease.

Ophthalmology Times: Ebola and the eye

Ebola is a hemorrhagic fever and is caused by a filovirus (RNA), similar to West Nile Virus. Dr. Kalayjian says symptoms include fever, gastrointestinal problems such as diarrhea, nausea, and vomiting, dehydration, sepsis, and disseminated coagulation. The mortality rate has varied greatly, but about 40 percent of those infected died during the most recent epidemic.

The virus has an animal reservoir and is found in great apes and fruit bats. Human-to-human transmission occurs through direct contact with the bodily fluids from an infected patient currently exhibiting symptoms, which is why it was common during the most recent outbreak to see healthcare providers in West Africa in head-to-toe protective gear.

“Prevention involves extraordinary body-contact precautions,” says Dr. Kalayjian. “This level of protection is unprecedented and was previously required only in research settings with high concentrations of various pathogens.”

Why should eyecare providers still care about Ebola? Dr. Kalayjian says there are very important ocular complications that occur with Ebola.

“One of the interesting complications from Ebola has to do with the immunology of the eye,” he says. “The eye is a site of immune privilege. The ocular complications appear in people who have survived the initial infection, and these complications generally occur months later-probably because the initial infection within the eye did not provoke an immune response and consequently will present much later.”

Ocular symptoms include chorioretinal scars, anterior/posterior uveitis, and vitritis.

Related: Implementing advanced concepts in the management of uveitis

Dr. Kalayjian says there have been rapid and promising developments in the creation of an Ebola vaccine, with several vaccines in development. 

“I can’t emphasize enough how important vaccines are in curtailing epidemics but also in preserving human health,” he says.

Next: Zika

Zika

Zika virus is the infectious disease epidemic of the moment. The mosquito-borne disease can present as fever, lymphadenopathy, and conjunctivitis.

Overall, Dr. Kalayjian says Zika is a much more mild disease than dengue or chikungunya, which are both spread by the same mosquitos. However, the main concern with Zika is that babies whose mothers contracted the disease while pregnant were born with microcephaly. The CDC has strongly advised pregnant women from traveling to countries where Zika is confirmed.

Although a number of Americans were infected after traveling outside of the U.S., no cases to date have originated in the mainland U.S. Local mosquito-borne cases have been reported in the Commonwealth of Puerto Rico, the US Virgin Islands, and America Samoa. Due to Zika’s rapid spread throughout Latin America and the disease’s ocular symptoms, Rachel Grant, OD, shared her advice for diagnosing Zika in your practice. Read her advice HERE.