University Times

With all the talk of potential avian flu pandemics or bioterrorism in the news, it’s hard to know who or what to believe.

In the third talk in the University’s six-part mini-medical school community health education series, a trio of disease fighters described their roles in the battle against the viruses and bacteria that can cause outbreaks of illness in humans.

The May 16 talk featured Pitt researchers Andrea Gambotto and Simon Barratt-Boyes, co-developers of an avian flu vaccine, and Lee H. Harrison a former Epidemic Intelligence Service (EIS) officer with the Centers for Disease Control and Prevention (CDC). Barratt-Boyes discussed how diseases can make the jump from animals to humans, while Gambotto offered details about the new genetically engineered avian flu vaccine and how it works.

Harrison, an epidemiology professor in the Graduate School of Public Health (GSPH), began the evening’s session by sharing his experience as a front-line EIS investigator into the causes of disease outbreaks.

Although EIS may not be a familiar name, its work is well known. EIS officers have figured prominently in a number of high- profile health-related headlines including the eradication of smallpox and polio, the discovery of how AIDS is transmitted and response to terrorist attacks, including 9/11.

More recently, EIS officers responded to the October 2001 anthrax attacks, the 2004 salmonella outbreak that was traced to tomatoes from Sheetz stores and, closer to home, the 2003 Chi-Chi’s hepatitis outbreak in Beaver County that sickened 660 people and eventually killed four.

The CDC program has been in existence since 1951, when it was developed as a way to train physicians and scientists in detecting early signs of biological warfare. EIS officers, who serve two-year assignments, now number in the thousands.

During his own tenure as an EIS officer, Harrison investigated an outbreak of food-borne illness in Peru, anthrax among the Lengua Indians in Paraguay, a meningitis outbreak among Hajj pilgrims returning from Mecca, pinkeye at a New Mexico Navajo boarding school and meningitis among children on a Lexington, Va. school bus.

He drew on his personal experience in investigating a mystery illness that was killing Brazilian infants and children in a small town near São Paulo to describe how EIS officers seek causes and cures for disease outbreaks.

“You go into it having no idea of what it is or what is causing it,” he said. The purpose of an outbreak investigation is threefold, he told the Scaife Hall audience. The first goal is to identify the infectious agent. “Once you’ve got the bug you can begin to address how to treat it,” Harrison said. Second, it’s important to identify the source and the risk factors for the illness. “You want to be able to nip it in the bud,” he explained.

And, finally, and most important: “You want to control the outbreak.”

Two decades ago, Harrison was among the investigators summoned by Brazilian health officials to the town of Promissao, near São Paulo, where young children were dying within hours of coming down with a fever and a rash. Although the symptoms appeared to be similar to meningitis, tests for the disease were negative.

The first practical step in an outbreak investigation: “Listen to the person who picks you up at the airport,” Harrison said. “Very often they have been very involved in the outbreak” and can offer valuable information.

In this case, he learned that the children who were becoming ill had recently had pinkeye, a fact that later proved to be key.

Next, investigators confirm that there actually is an outbreak and verify the diagnosis by examining victims. They then methodically define and identify each case and describe the outbreak in terms of time, person and place.

Armed with the factual information, a hypothesis is developed and tested until control and prevention activities can be implemented.

The hypothesis they developed in Promissao was that the disease was a bacterial infection and that pinkeye put children at risk for it.

During the Promissao outbreak no infectious agent was identified but in a second outbreak the following year in a nearby region, blood cultures were able to shed some light on the cause: haemophilus aegyptius, which typically causes benign pinkeye. “Actually it was one of the first bacteria discovered in the 1880s,” Harrison said, adding that it didn’t make sense that this organism might be killing young children. DNA testing later found that this disease, which became known as Brazilian Purpuric Fever (BPF), was caused by a new clone of the bacteria. “We found there was an extra piece of DNA… which was unique to the new strain,” he said. That extra DNA allowed the relatively benign bacteria to become more virulent. “It appeared to be a mutant strain,” Harrison said.

A case study showed a correlation between exposure to pinkeye and the subsequent fever.

“We now knew the cause and needed to work quickly to prevent the spread,” Harrison said. “We knew if it got to the city of São Paulo we’d have a massive outbreak.”

The idea of developing a vaccine was considered, but a simple solution was found: Instead of treating the children’s pinkeye with eyedrops that would cure the pinkeye but leave bacteria elsewhere in the body, oral antibiotics were substituted. Because they circulated through the entire body, the bacteria were killed throughout.

The final step in such an investigation, Harrison said, is to communicate the findings in scientific literature to inform the medical community.

The team published their results on the CDC’s Morbidity and Mortality Weekly Report (MMWR) and in the Brazilian literature to inform others in the health care community. MMWR is available on line at cdc.gov/mmwr and, Harrison said, is a reliable source for information on emerging disease outbreaks.

Animal-human transmission of diseases

More than 200 diseases are known to be transmittable from humans to animals or vice versa, said Simon Barratt-Boyes, an associate professor in the GSPH Department of Infectious Diseases and Microbiology. Among them are zoonotic diseases such as rabies, West Nile fever, hantavirus pulmonary syndrome and avian flu that may be transmitted from animals to humans.

The process of zoonosis most often refers to diseases transferred to humans by other vertebrates, he said.

Barratt-Boyes noted that zoonotic diseases frequently arise from tropical areas, citing West Nile fever and Dengue fever as examples.

“It’s interesting to note that some of these fairly obscure diseases that we don’t hear about develop the ability to spread to temperate countries like the United States,” he said, adding that it’s likely such diseases will continue to emerge.

He predicted global warming will contribute to the rise of zoonotic diseases as they adapt to temperate climates. Sprawl also will play a role as people spread further into areas where diseases such as rabies and hantavirus exist.

The best-known of the zoonotic diseases is rabies, a virus that can infect humans directly or be transmitted by creatures such as raccoons, skunks, foxes and coyotes. The almost-always fatal disease has declined in domestic animals since the 1950s thanks to vaccination requirements. But the overall number of animal cases has tripled due to increasing numbers of cases in the wild. “Rabies is not going away,” he said.

A zoonotic disease that is on the rise in humans is West Nile virus. “It’s not an uncommon infection,” Barratt-Boyes said, noting that nearly 1,000 cases have been reported in California.

The disease is transmitted by mosquitoes and typically cannot be passed from person to person. Although most people who are infected have mild symptoms or none at all, about 1 in 150 will develop illness that can include fever, headache, disorientation, convulsions, vision loss and paralysis. In severe cases, the neurological effects may be permanent.

Prevention of West Nile virus is centered around the use of insect repellent, avoiding mosquitoes and eliminating mosquito breeding sites.

A relatively new zoonotic disease is hantavirus pulmonary syndrome, identified in 1993. Symptoms of hantavirus include fever, muscle pain, headache, chills, dizziness, cough and gastrointestinal symptoms, making it difficult to diagnose. The potentially deadly disease is spread through the urine, droppings or saliva of rodents.

Cases in the United States are concentrated in the West and Southwest; it also is present in Central and South America. Typically, humans are infected by inhaling the virus, although human-to-human transmission is suspected in South America. There is no treatment, Barratt-Boyes said.

Although the domestic house mouse is not a carrier of hantavirus, other rodents such as deer mice, white-footed mice, cotton rats and rice rats harbor the disease, and controlling such rodents is the main weapon against the virus, Barratt-Boyes said.

The zoonotic disease getting the most attention by far today is avian flu. Vaccination will be the main tool to fight an avian flu pandemic along with attempts to eliminate the virus from avian sources, something Barratt-Boyes said is a Herculean task.

Because the flu virus is harbored in migrating aquatic birds, effectively controlling it is difficult, since wild bird flyways span national borders and continents. “One of the very scary things about avian influenza is the speed with which the virus can act,” he said, noting that there have been three flu pandemics in the past century alone.

“The risk is that the virus will develop the ability through the mutation of certain genes to develop the ability to spread human-to-human,” he said.

He cautioned listeners to be aware of zoonotic diseases, but to take precautions based on an assessment of one’s own risk for a particular disease. He also urged the audience not to believe everything they read, but to use reliable sources for information.

“I think the Internet is a great place to look,” he said, but cautioned that not everything is trustworthy. “I’d stick to CDC and NIH (National Institutes of Health), not individuals’ web sites,” he said.

A new avian flu vaccine

Researcher Andrea Gambotto, an assistant professor of surgery and of molecular genetics and biochemistry in the School of Medicine, wrapped up the evening with a discussion of how flu vaccines are developed and, more specifically, Pitt researchers’ development of an avian flu vaccine that has been proven effective in animal models.

The influenza virus, Gambotto said, is a zoonotic disease that sometimes is transmitted between animals and humans.

Avian influenza, which has been documented as the cause of 115 deaths among more than 200 identified human cases, has spread throughout Asia and now is being found in Europe and Africa, mainly in the wild bird population.

Unlike forms of flu that mainly affect the upper respiratory system, the H5N1 avian flu (named for the specific proteins it uses to attach to the cells it infects) is particularly deadly because it can infect multiple body systems including the kidneys, central nervous system and liver.

Medication such as oseltamivir (Tamiflu) can treat it, but vaccines are needed for prevention.

The new generation of vaccines Gambotto’s group is working on are genetically engineered live viruses that are delivered using the common cold virus, rather than inactivated traditional vaccines that are used for other influenza viruses.

Although inactivated virus vaccines are safe, easy and relatively inexpensive to produce, they have a number of disadvantages.

They stimulate only one aspect of the immune response — the production of antibodies — and offer only a short period of immunity, hence the need for annual flu shots.

But Gambotto said the biggest limiting factor is that these vaccines must be produced in fertilized eggs, which limits production capacity.

Genetically engineered vaccines, on the other hand, are used by taking a common cold virus and deleting the parts it uses to replicate, while inserting fragments of the proteins found in the avian flu virus to form a hybrid that can infect cells, stimulating immunity, but can’t replicate.

“It makes the immune system think it’s infected with influenza, but it’s just a common cold virus,” he explained.

Among the advantages of genetically engineered live vaccines are that they stimulate both the humoral immune response (production of antibodies) and a cellular response in the T-cells, producing a broader, stronger immunity. Disadvantages include the chance that a person may already have a pre-existing immunity to the cold virus that is used to deliver the vaccine.

In Gambotto’s experiment, most of the mice that received the vaccine survived exposure to the H5N1 virus, while all those who were not vaccinated died. Subsequent tests in chickens showed that all those that received an injection of the vaccine survived exposure to the H5N1 infection; half the chickens that were immunized through the nose survived the virus, and all those who received no vaccine died.

“Now we are at the stage where we have to test the safety and efficacy of the vaccine in humans,” Gambotto said, adding that the team is waiting for funding to do so.

In addition to being effective, Gambotto said the genetically engineered vaccine has the advantage of being able to be generated quickly.

Current technology allows such a vaccine to be developed within 30 days, which Gambotto said would be very important in case of a pandemic.

And the vaccine can be produced in large quantities, without the need for fertilized eggs. “Basically there is no limit,” he said, adding that the 2 billion to 4 billion doses experts estimate would be needed during a pandemic could be produced through cell culture systems.

“If a pandemic hits, we won’t have much time,” he said.

—Kimberly K. Barlow