Travelers Should Be Aware of Seasonal Influenza Transmission

Travelers Should Be Aware of Seasonal Influenza Transmission Due to its New Spre

In most parts of the world — and in developing nations in particular — cities and rural areas are becoming more densely populated and more interconnected. This makes it easier for germs to spread from person to person as well as from animals to people.People are traveling more often and to more-remote places than ever before — and so are germs. Because global travelers may be exposed to microbes to which they have no natural immunity, they're at increased risk of contracting an infectious disease, carrying it home with them and then spreading it to others.


Climate change, the destruction of habitat and the spread of humans into previously unpopulated areas have all contributed to the emergence of certain pathogens. When humans alter or encroach on a native habitat, especially one that is still relatively biodiverse, the stage is set for an emerging disease — not because a new microbe suddenly develops, but because humans come in contact with it for the first time.Historically speaking, the current pattern of emerging diseases isn't new. Certain aspects of modern life make it easier for some diseases to flourish and for researchers to identify them. And the immediacy and ubiquity of modern communications bolsters the perception that we live in unusually threatening times.

Influenza (also called flu) is a viral infection of the nose, throat, trachea, and bronchi (air passages). Outbreaks of flu occur almost every year, usually in late fall and winter.Influenza (or flu) is a highly contagious viral respiratory tract infection. An estimated 10 to 20 percent of the population in the US contract influenza each year. Influenza is characterized by the abrupt onset of fever, muscle aches, sore throat, and a nonproductive cough.

Flu viruses cause more severe symptoms and can cause more severe medical problems than cold viruses. Older adults, people whose immune systems are impaired, and people with chronic medical problems are particularly at risk for more severe flu symptoms or complications.

There are several types of influenza viruses and these are specific to species ie. there are separate influenza viruses for birds,cats and humans ect. that dont normally cross the species barrier.Avian influenza is a disease of birds,it doesnt effect human except in rare cases such as bird flu.

The 2007 World Health Day slogan ‘Invest in health, build a safer future’addresses one of the most vital concerns of out times. Globalization, rapid travel and trade make it much easier for new and existing diseases to leap over national borders and threaten our collective security. Avian Influenza in 2006 and SARS in 2003 spread from one country and region to the next.New diseases have appeared and old ones have re-emerged as epidemic/pandemic prone diseases to present an acute threat to life. Climate change, natural disasters, chemical and nuclear accidents and bioterrorism also hold the potential to threaten international public health security.

Researchers studying influenza transmission patterns in the Southern Hemisphere and in tropical areas, specifically Brazil, uncovered the unexpected finding that each season influenza travels from low populated regions near the equator to the more populated centers. Their work, funded by the Fogarty International Center (NIH), part of the National Institutes of Health (NIH), can improve planning for influenza control in tropical areas.

In their paper, "Seasonality of Influenza in Brazil: A Traveling Wave from the Amazon to the Subtropics," to be published in the American Journal of Epidemiology, the researchers document the seasonal spread of influenza viruses and seasonal mortality patterns associated with influenza across Brazil. The interest in Brazil arises because the country covers a range of latitudes and crosses several regions, including tropical and sub-tropical climates.

"This study contributes to the understanding of the role of tropical regions in the global circulation of influenza. It has direct implications for public health by offering guidance for the timing of delivery and composition of influenza vaccines," said Dr. Mark Miller, a co-author and Associate Director for Research at FIC.

As epidemic months of influenza in Brazil are triggered earlier in the year in the equatorial regions, vaccine recommendations using formulations from the Northern Hemisphere could be more appropriate for some countries in the Southern Hemisphere near the equator. This point is becoming increasingly important as more tropical countries introduce and use substantial quantities of vaccine.

Brazilian investigators worked with colleagues at FIC and the National Institute of Allergy and Infectious Diseases (NIAID) in revealing the unexpected spatial transmission patterns in the annual seasonality of influenza across a large area of the South American continent.

Brazil is nearly the same size as the United States. However, most of Brazil's territory lies in the tropical belt. This aspect makes the study valuable since less is known about the circulation of influenza viruses at these latitudes and how epidemics bridge and annually alternate between both hemispheres following the winter seasons.

Given the range of latitude encompassed by Brazil which crosses the equatorial and the southern tropic lines and using sophisticated mathematical analytical tools, the researchers studied the mortality data of influenza and pneumonia from two decades, together with laboratory confirmed data from recent years.

Both sets of independent data sources converged to show that, surprisingly, in Brazil influenza epidemics do not spread from where the highest human population densities are found, but rather from the equator towards more populous regions of the Southeast and South of Brazil.

The study, supported by FIC, results from a collaboration among researchers in different parts of the world. Study authors are Wladimir J. Alonso (FIC), Cécile Viboud (FIC), Lone Simonsen (NIAID), Eduardo W. Hirano (Mechanical Engineering Department, Universidade Federal de Santa Catarina, Florianópolis, Brazil), Luciane Z. Daufenbach (Secretariat of Health Surveillance, Ministry of Health, Brasília, Brazil), and Mark A. Miller (FIC).

When health emergencies give rise to global concerns, an effective response requires international coordination as has been seen post tsunami and the SARS outbreak. The WHD slogan highlights the crucial need to invest in human resources and strengthened health systems to enable the international community to effectively meet the public health risks and challenges. WHO is assisting countries to strengthen their public health capabilities. The revised and broadened International Health Regulations (2005) which will come into force in June 2007 will provide an important instrument to protect countries from global health destabilization.

Under this international agreement, WHO Member States are obliged to prevent and control the spread of disease inside and outside their borders. They are required to maintain core surveillance and response capacities to detect, assess, notify and report public health events to WHO and to respond to public health risks and public health emergencies.

Flu vaccinations have been used to diminish the effects of the flu season. Since the Northern and Southern Hemisphere have winter at different times of the year, there are actually two flu seasons each year. Therefore, the World Health Organization (assisted by the National Influenza Centers) makes two vaccine formulations every year; one for the Northern, and one for the Southern Hemisphere.

After You Return from an Infected Area :

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