Study: Indirect transmission can trigger influenza outbreaks in birds

New data on the persistence of avian influenza viruses in the environment has allowed a team of University of Georgia researchers to create the first model that takes into account both direct and indirect transmission of the viruses among birds. The model, which is detailed in the early online edition of the journal Proceedings of the National Academy of Sciences, has the potential to shed new light on how outbreaks begin in wild bird populations.

“The environmental transmission of avian influenza among birds is quite rare, but our model shows that it can play an important role in outbreaks,” said lead author Pejman Rohani, professor in the UGA Odum School of Ecology. “There are situations where ignoring the possibility of environmental transmission would cause you to significantly underestimate the probability, magnitude and duration of an outbreak.”

Rohani explained that current models of avian influenza only take into account the direct transmission of the virus that occurs when infected waterfowl and shorebirds shed the virus in their feces and those nearby drink contaminated water. But research in the UGA College of Veterinary Medicine has revealed that some avian influenza viruses can persist in water for up to 150 days. So even when no infected birds are present, Rohani said, virus present in the water can trigger an outbreak. Models that only take into account direct transmission, he pointed out, would incorrectly conclude that there’s no risk of an outbreak when no infected birds are present.

The viruses the researchers studied are known as low-pathogenicity viruses and do not infect humans. Low-path viruses only cause mild symptoms in birds but have the potential to swap genes and give rise to high pathogenicity viruses that can cause massive die-offs in poultry and—in rare cases—can infect humans. The H5N1 avian influenza virus, for example, has a 60 percent mortality rate in humans and is responsible for 262 deaths worldwide since 2003, according to the World Health Organization.

“We need to understand low-path viruses because they are a storehouse of genetic variation that can give rise to new and potentially dangerous strains,” said study co-author John Drake, assistant professor of ecology.

In addition to the environmental persistence of the virus, the team’s model takes into account variables such as lake size and the rate at which infected birds recover to describe likely and worse case outbreak scenarios. The model also reveals that environmental transmission extends the duration of an outbreak by infecting birds that haven’t come into contact with other birds yet have consumed contaminated water.

The data on the environmental persistence of avian influenza viruses comes from the lab of David Stallknecht, associate professor in the department of population health in the UGA College of Veterinary Medicine. In a study recently published in the journal Veterinary Microbiology, Stallknecht and lead author Justin Brown determined the persistence of 12 low-path avian influenza viruses under natural ranges of pH, salinity and temperature.

The researchers found that the duration of persistence varied widely among viruses, but that the viruses generally are most stable at a slightly basic pH, temperatures of less than 63 degrees Fahrenheit (17 degrees Celsius) and in fresh to slightly brackish water.

“The role of the environment in the transmission of avian influenza has been almost completely undefined, and that’s what makes this research so exciting,” said Brown, a post-doctoral researcher. “Migration and other factors relating to the biology of the avian host are still very important factors that drive the epidemiology of avian influenza, but now we can look at various environments and ask if they’re better or worse for the transmission of avian influenza.”

The research was funded by the Centers for Disease Control and Prevention, the Morris Animal Foundation, the James S. McDonnell Foundation and the Southeastern Cooperative Wildlife Disease Study.

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Statement by HHS Secretary Kathleen Sebelius and Acting CDC Director Dr. Richard Besser Regarding the Change in CDC's School and Childcare Closure

Statement by HHS Secretary Kathleen Sebelius and by Acting CDC Director
Dr. Richard Besser

Since the beginning of this outbreak, the CDC has been working to
update, or in some cases, quickly develop interim guidelines to help
healthcare providers, health departments and communities take effective
action to prevent the spread of this novel H1N1 virus. In doing so, we
acknowledged that our interim guidelines would be based on the data
available at the time, be guided by science, and designed so that
resources and efforts would be directed toward actions and activities
that would make a difference in preventing spread of this virus. If new
information or developments indicated a need to adjust our guidance, we
indicated we would do so.

Today, we are announcing a change with respect to CDC's interim guidance
on closing schools and childcare facilities. The initial guidance CDC
issued on May 1st recommended that affected communities with
laboratory-confirmed cases of influenza A H1N1 consider adopting school
dismissal and childcare closure measures, including closing for up to 14
days depending on the extent and severity of illness. At the onset of
this outbreak of a previously unknown influenza virus, we believed it
could be helpful to close affected schools while we learned more about
the virus's transmission and the severity of disease. Further, the U.S.
national strategy for pandemic influenza suggested that ongoing
community-wide closure of all schools and daycare centers should be
considered in the event of a severe outbreak, especially if these
measures could be implemented early.

As CDC's daily press briefings have illustrated, much has been learned
quickly about the virus's severity and its spread. We now believe that
the disease currently being caused by this novel flu virus is similar to
that typically caused by seasonal influenza. Although many people will
get sick and a small number, unfortunately, may become quite ill or even
die, the available data do not indicate that this virus is causing
unusually severe influenza at this time.

With the modified policy being issued today, CDC no longer recommends
that communities with a laboratory-confirmed case of influenza A H1N1
consider adopting school dismissal or childcare closure measures.
Rather, in line with policies being undertaken in Seattle, New York and
Canada, CDC has modified its policy to recommend implementation of
measures that focus on keeping all student, faculty and staff with
symptoms of influenza out of schools and childcare facilities during
their period of illness and recuperation, when they are potentially
infectious to others.

More specifically, at this time, CDC recommends the primary means to
reduce spread of influenza in schools focus on early identification of
ill students and staff, staying home when ill, and good cough and hand
hygiene etiquette. Students, faculty or staff with influenza-like
illness (fever with a cough or sore throat) should stay home and not
attend school or go into the community except to seek medical care for
at least 7 days even if symptoms resolve sooner. Students, faculty and
staff who appear to have an influenza-like illness at arrival or become
ill during the school day should be isolated promptly in a room separate
from other students and sent home.

It's important to note that schools that were closed based on previous
interim CDC guidance related to this outbreak may reopen. That said,
decisions about school closure are at the discretion of local
authorities based on local considerations, including public concern and
the impact of school absenteeism and staffing shortages.

We appreciate the efforts that communities, particularly school
districts, have taken to protect students and staff from this influenza
A H1N1 virus. Communities and schools are at the forefront of
protecting people's health, and we are committed to providing them the
flexibility they need to deal with local conditions, and the best
possible guidance that reflects our most current understanding of the
scientific and medical facts.

Finally, we should add that there are many individuals in our
communities -- the elderly, the very young, and individuals with
suppressed immune systems -- for whom influenza represents a potentially
lethal threat. The 2009 influenza A H1N1 virus is likely to circulate
widely in our communities; if not now then almost certainly in the fall.
We all have a special responsibility during this time to protect
ourselves and protect our neighbors and others in our community by
behaving responsibly and doing whatever we can to minimize the spread of
disease. A virus that may only cause sniffles and mild inconvenience in
one person may put the next into the hospital.

We have more information on the 2009 H1N1 virus today than we did only
one week ago, but much uncertainty remains. We should all be prepared
for a potentially rocky influenza season this fall. The Administration
and the CDC will continue to actively investigate this outbreak as it
unfolds and protect the health of the American public.

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From Swine Flu to Dengue Fever: Infectious Disease Risks on the Rise

Emory University environmental studies professor Uriel Kitron was in Australia last week, assisting health authorities in an outbreak of dengue fever in the state of Queensland, when news broke about the swine flu epidemic in Mexico.

Global travel and human alterations to the environment, such as rapid urbanization, are helping to fuel some infectious diseases outbreaks, says Kitron, also chair of the environmental studies department at Emory and an internationally known researcher of the eco-epidemiology of infectious diseases. Kitron's research focuses on vector-borne diseases carried by insects and ticks and the zoonoses – diseases shared by humans and animals.

"In many developing countries, people are moving from rural areas to mega-cities, where they continue to practice subsistence agriculture," Kitron says. "Whenever you have large concentrations of people, domestic animals and poor sanitation and water supply, you have many opportunities for disease transmission."

Deforestation and other human changes to the landscape are other drivers of emerging infectious diseases, he added. "For example, when you bring agriculture into formerly forested areas, you change the migration patterns of animals and expose people and their livestock to more contact with wildlife," he explains.

Stemming Dengue Fever in Australia

Unusually hot, wet weather, a rapidly developing strain of the dengue virus, and a human traveler created "a perfect storm" for dengue fever in Queensland, Australia – which is experiencing its worst outbreak in two decades. About 1,000 people have become ill with the mosquito-borne illness. Dengue fever causes severe headaches and joint pain, and exposure to a second strain can result in hemorrhagic fever and death.

Kitron joined other experts in assisting Queensland health authorities. Kitron specializes in spatial epidemiology – using geographic information systems (GIS) and other methods to gather environmental data and create maps to pinpoint disease agents and their vectors in time and space.

The outbreak was traced to a patient who had recently traveled to Papua, New Guinea. "Although quite sick, he didn't go to a doctor for several weeks," Kitron says. "Whenever you have a lag time in diagnosis like that, you miss opportunities to prevent the spread of an outbreak."

Queensland's public health efforts – combined with cooler, drier weather – appeared to have stemmed the dengue fever outbreak for now. However, Kitron says the virus may be re-introduced, or could over-winter and re-emerge in the next hot season.

The Queensland government is now considering investing in spatial analysis software. Kitron plans to return for a workshop on using the technology to aid in the response for future outbreaks.

"Use of GIS and spatial statistics can help health authorities determine which cases are more likely to lead to other cases, so that they can better target which houses should be sprayed for mosquitoes immediately, and which ones can wait," Kitron explains.

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FDA Warns Consumers Nationwide Not to Eat Certain Types of Raw Red Tomatoes

The Food and Drug Administration is expanding its warning to consumers nationwide that a salmonellosis outbreak has been linked to consumption of certain raw red plum, red Roma, and red round tomatoes, and products containing these raw, red tomatoes.

FDA recommends that consumers not eat raw red Roma, raw red plum, raw red round tomatoes, or products that contain these types of raw red tomatoes unless the tomatoes are from the sources listed below. If unsure of where tomatoes are grown or harvested, consumers are encouraged to contact the store where the tomato purchase was made. Consumers should continue to eat cherry tomatoes, grape tomatoes, and tomatoes sold with the vine still attached, or tomatoes grown at home.

On June 5, using traceback and other distribution pattern information, FDA published a list of states, territories, and countries where tomatoes are grown and harvested which have not been associated with this outbreak. This updated list includes: Arkansas, California, Georgia, North Carolina, South Carolina, Tennessee, Texas, Belgium, Canada, Dominican Republic, Guatemala, Israel, Netherlands, and Puerto Rico. The list is available at www.fda.gov/oc/opacom/hottopics/tomatoes.html#retailers. This list will be updated as more information becomes available.

FDA’s recommendation does not apply to the following tomatoes from any source: cherry, grape, and tomatoes sold with the vine still attached.

FDA recommends that retailers, restaurateurs, and food service operators not offer for sale and service raw red Roma, raw red plum, and raw red round tomatoes unless they are from the sources listed above. Cherry tomatoes, grape tomatoes, and tomatoes sold with the vine still attached, may continue to be offered from any source.

Since mid April, there have been 145 reported cases of salmonellosis caused by Salmonella Saintpaul nationwide, including at least 23 hospitalizations. States reporting illnesses linked to the outbreak include: Arizona, California, Colorado, Connecticut, Idaho, Illinois, Indiana, Kansas, New Mexico, Oklahoma, Oregon, Texas, Utah, Virginia, Washington, and Wisconsin. Salmonella Saintpaul is an uncommon type of Salmonella.

Salmonella can cause serious and sometimes fatal infections particularly in young children, frail or elderly people, and those with weakened immune systems. Healthy persons often experience fever, diarrhea (which may be bloody), nausea, vomiting, and abdominal pain. In rare circumstances, the organism can get into the bloodstream and produce more severe illnesses. Consumers who have recently eaten raw tomatoes or foods containing raw tomatoes and are experiencing any of these symptoms should contact their health care provider. All Salmonella infections should be reported to state or local health authorities.

FDA recognizes that the source of the contaminated tomatoes may be limited to a single grower or packer or tomatoes from a specific geographic area. FDA also recognizes that there are many tomato crops across the country and in foreign countries that will be ready for harvest or will become ready in the coming months. In order to ensure that consumers can continue to enjoy tomatoes that are safe to eat, FDA is working diligently with the states, the Centers for Disease Control and Prevention, the Indian Health Service, and various food industry trade associations to quickly determine the source of the tomatoes associated with the outbreak.

FDA is taking these actions while the agency continues to investigate this outbreak with state and federal partners. Such actions are a key component of FDA’s Food Protection Plan, a scientific and risk-based approach to strengthen and protect the nation’s food supply.

FDA will continue to issue updates as more specific information becomes available.