Graphical Headline September 2, 2002

The March West
 If you believed the media reports over the last few weeks, the United States is in the middle of a serious public health crisis. What started in 1999 with a few suspicious deaths in New York has become a national health concern. People are dying of West Nile virus.

Slowly but surely, West Nile virus has made its way down the East Coast into the southeastern United States and then started creeping westward. As the summer of 2002 comes to a close, the virus has now spread to all but seven western states, Hawaii, and Alaska. (Click here to see a map showing how the virus has spread from 1999 to the present.) In 2002, there have been confirmed deaths from West Nile virus in Louisiana, Ohio, Michigan, Illinois, Kentucky, New York, Maryland, Georgia, Mississippi, and Texas. As of the Labor Day weekend, there were 28 confirmed dead and hundreds more infected. Louisiana and Mississippi have been particularly hard hit.

The biggest concern with the spread of West Nile virus is that it has now reached the warmer southern states, where mosquitoes are active year-round. Unfortunately, it is this same warm weather that has historically attracted the more vulnerable elderly population who either retire to these states or spend their winters there. Therefore, in Gulf Coast states such as Florida, Louisiana, and Texas, tracking West Nile virus and controlling mosquito populations must continue 12 months a year.

How dangerous is West Nile virus? Data suggest that the public should take some precautions against West Nile-carrying mosquitoes, but not overreact. In states where West Nile virus has been observed, less than one percent of mosquitoes are actually infected with the virus. The virus can only be passed to humans by the bite of an infected mosquito and not every bite by an infected mosquito will lead to an infection. In almost all of the cases where a healthy human gets infected with West Nile virus, that person will have few, if any, symptoms. Some people may develop mild, flu-like symptoms — fever, body aches — but will most likely never even realize that these symptoms are caused by West Nile virus. Less than one percent of those infected with West Nile virus will develop a serious illness.

The people who are most at risk of getting seriously ill from West Nile virus are the very young, the elderly, and those people with weakened immune systems, such as cancer patients undergoing chemotherapy. But to be safe, everyone can take these simple precautions to reduce their exposure to mosquitoes: 1) stay indoors at dawn and dusk when mosquitoes are more likely to bite; 2) wear long-sleeved shirts and long pants when you have to go outside; and 3) spray yourself and your clothing with an insect repellent containing DEET. If you're still worried, try reading "Should I Worry About West Nile Virus?" from TeensHealth.

More Links
Students can get more background information about the West Nile virus and how it was initially detected in the United States by reading the Riverdeep Current archive story, "Tracking the West Nile Virus."

Read a recent report from CNN.com, "CDC: West Nile death toll reaches 20."

"West Nile Outbreak May Peak Soon" a United Press story from MedlinePlus

The National Library of Medicine's MedlinePlus page of West Nile virus information links

Extensive information on West Nile virus from the Center for Disease Control (CDC)

Learn About the Problem
 For help in understanding bar charts/ bar graphs, encourage your students to work through the following Riverdeep activities:
  • Snack-O-Gram from Tangible Math's Mathematics Toolbox unit. This activity focuses on the usefulness of bar charts for comparing quantities.

  • Data Displays from Tangible Math's Stats! unit. This activity introduces the powerful data display functions of the Stats! tool.

  • Exploring Bar Graphs from the Fundamental Statistics module of Destination Math, Mastering Skills & Concepts V: Pre-Algebra.

Your students can simulate what happens when a virus is introduced into a population of rabbits in the Logal High School Biology Explorer activity, Introducing a Virus.

Think About the Problem
  1. Birds are a crucial part of the West Nile virus transmission chain. Mosquitoes become infected when they feed on infected birds. The infected mosquitoes then transmit the virus to other birds — or to humans and other animals. Therefore, public health researchers have not only been testing mosquito populations for the presence of West Nile virus, but they have tested birds as well. Many states even have Web sites where citizens can report dead birds to public health researchers. Examine the bar graphs showing the number of cases of birds testing positive for West Nile virus in Maryland and Florida so far this year. Use the bar graphs to answer the following questions:

    • How many Maryland birds tested positive for West Nile virus in the week ending July 19?

    • In what week were the most birds tested positive for West Nile virus in Maryland? In Florida?

    • In what month were the most birds tested positive for West Nile virus in Maryland? In Florida?

    • In Maryland, why do you think there is no data recorded before the week ending June 14?

    • Maryland reports no new cases of West Nile virus in sampled birds for the weeks ending August 9 and August 16. Does that mean the virus is no longer a threat in Maryland? Why is it important to see data for the remainder of August?

    • How is the bar chart for Florida different from the bar graph for Maryland? What effect would the weather in a state like Florida or Louisiana have on their bar graphs? Would you expect West Nile virus to be more of a year-round threat in these states? Why?

    Interested in West Nile Virus data from other states? Visit the USGS Center for Integration of Natural Disaster Information's West Nile Virus site.

  2. Students can identify the process by which the West Nile virus is spread and design their own plan to prevent the spread of the virus in their community or state with this standards-linked lesson plan from CNN Student News, "Planning for the prevention of the West Nile Virus"

  3. How is the spread of a mosquito-borne disease like West Nile virus different than the spread of the flu virus? Students can start researching flu with the Riverdeep Current archive story, "Flu Season: Added Worries?" and the Flu Season 2002-03 site from the CDC's National Immunization Program.

  4. Use the following questions in open-ended class discussions: Are students concerned about contracting West Nile virus themselves? Are they worried about siblings, parents, or grandparents contracting West Nile virus? Should Americans be concerned about a West Nile virus epidemic in the remainder of 2002? What do students think will happen with West Nile virus in 2003 and 2004?
 Fluffy and Fido
Of course, mosquitoes don't only bite people. Any animal that is outdoors might be bitten by an infected mosquito and contract West Nile virus. There have been a few cat deaths; about 10% of dogs in affected areas have been exposed to West Nile virus, but none have become critically ill.

In Kentucky, where horses are a multi-million dollar industry, 44 horses have tested positive for West Nile virus this year. Several horses have died. Racetracks and horse farms are taking preventive measures to control the horses' exposure to mosquitoes. For more, read the CNN.com article, "Kentucky horse racers battle West Nile virus."

A Shot in the Arm
Researchers began working on a vaccine for West Nile virus as soon at the virus appeared in New York in 1999. They have created a vaccine by implanting West Nile virus genes into a harmless form of dengue virus. Early tests of the vaccine on mice show that it does protect them from West Nile infection. Trials of the vaccine are currently underway with monkey and clinical trials with humans should start by the end of the year.

Extending the Problem

  1. West Nile virus is not the only deadly virus transmitted by mosquitoes. In fact, West Nile virus is very similar to the virus that causes St. Louis encephalitis. The St. Louis encephalitis virus has been found throughout the United States for decades. Since 1964, there have been over 4000 reported human cases of St. Louis encephalitis, averaging 128 cases annually with 30 deaths. The mortality rate for people infected with the St. Louis encephalitis virus may be double the rate of people infected with West Nile virus. Find out more about St. Louis encephalitis and Eastern Equine encephalitis with these articles from the Center for Disease Control (CDC):

  2. Have students research other mosquito-borne diseases, such as St. Louis encephalitis, Eastern Equine encephalitis, malaria, yellow fever, dengue fever, etc. What are the symptoms of these diseases? Where do they occur? How are they controlled? Have students present their research to the class. As a class, have students compare the diseases. If West Nile virus were able to cross the Atlantic Ocean in 1999 — presumably when an infected mosquito, bird, or person flew into New York from Israel by airplane — how likely is it that another disease not normally found in the United States could find its way here?

  3. Some people are less concerned over West Nile virus than over how public health officials and local governments are fighting West Nile. The North American Butterfly Association (NABA) is concerned that mosquito-control spraying of pesticides endangers non-target species, such as honeybees and butterflies and that it could wipe out insects needed by birds and small mammals as food. See their article, "Public Panic over West Nile Virus." For more on the controversy over mosquito-control spraying, visit the following sites:

Sentinel Chickens?
As luck would have it, chickens do not get sick from West Nile virus. However, if they get bitten by a mosquito that has the virus, the chickens' immune systems will start fighting the virus and producing antibodies, which can be observed in a blood test. Why is this important? Chickens are being used as virus sentinels — early lookouts for the "invasion" of West Nile virus. Small groups of chickens have been placed in Canada and now in California as part of disease vector programs.