STORY BYSummertime brings yet another-and rather surprising-reason to lower your blood pressure:
People with hypertension who become infected with West Nile Virus (WNV) are at greater risk for developing encephalitis, or inflammation of the brain, than those with normal blood pressure, according to a recent study. People who use drugs such as cocaine and amphetamines, which cause high blood pressure, are also at greater risk.
The study was led by Kristy M. Lillibridge, DVM, assistant professor of epidemiology at The University of Texas School of Public Health at Houston. Lillibridge is also a former US Centers for Disease Control and Prevention epidemic intelligence service officer who worked on the first outbreak of WNV in the United States in New York City in 1999.
Lillibridge, along with researchers from several local and national centers, analyzed data from 90 hospitalized WNV patients in a Houston WNV outbreak in 2002. Besides high blood pressure, other significant risk factors identified were age (being over 51) and being male.
"Prior to our study, the only significant risk factor identified was advanced age, that an older person was more likely to develop encephalitis," said Lillibridge.
In the New York City outbreak, diabetes was found to be a risk factor, also, Lillibridge says. "In this study, diabetes was not significant; and all diabetics who had developed encephalitis also had a history of high blood pressure ," Lillibridge says.
For most, risk is low. Less than 1 percent of
people who are bitten by mosquitoes develop any
symptoms of the disease and relatively few
mosquitoes actually carry WNV.
What Are the Symptoms of WNV?
WNV affects the central nervous system.
Symptoms vary.
Symptom information provided by the CDC
website: http://www.cdc.gov/ncidod/dvbid/
westnile/wnv_factSheet.htm
Not only did the study find a high proportion of patients with a history of high blood pressure who developed encephalitis, results also pointed to a higher proportion of encephalitis is persons using amphetamines or cocaine (eight percent), which are drugs known to cause high blood pressure.
"When we performed the statistical model using the data collected from all hospitalized patients, high blood pressure remained a significant risk factor, even when we adjusted for age and gender," Lillibridge says.
In the Houston outbreak, 59 patients developed encephalitis, 25 patients developed meningitis (inflammation of the membranes enclosing the brain and spinal cord), and six patients developed fever.
Although 60 percent of fatal cases involved women, 66 percent of the patients were men. Of the individuals who got WNV encephalitis, 76 percent had a history of high blood pressure or took drugs that cause high blood pressure.
Five children under 18 were also among the 90 patients studied. Of two who developed encephalitis, one had been taking amphetamines for attention deficit hyperactivity disorder; and one had a history of a head injury. When compared to the adults, the children had different symptoms, including seizures, rash, paralysis and diarrhea.
It is not known exactly why people with high blood pressure may be more susceptible to developing a more severe form of the disease. However, researchers hypothesize that it may be that high blood pressure allows the virus to cross more easily from the blood into the brain, resulting in the more serious symptoms associated with encephalitis.
Two other studies are about to be underway, according to Lillibridge. One will focus on the homeless population in Houston (10 percent of those who developed encephalitis in the original Houston group studied were homeless).
The other will be a national study of clinical features and risk factors for encephalitis in children.
"These studies help us better understand who is susceptible to serious disease, which will allow us to know who to target with messages about protection against mosquitoes bites," said Lillibridge. "People with high blood pressure and those who use drugs that produce high blood pressure should be especially careful to avoid infection by following simple precautions."
Lillibridge suggests
UPDATED: 4-05-2004
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Dr. Kristy Murray is an assistant professor in epidemiology at the UT School of Public Health.
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Tetanus booster for adults
Tetanus does not result from the rusty nail or whatever created the wound. The danger lies in the bacteria Clostridium tetani that lives in the soil or manure on that nail or gardening tool. When these spores get into a wound—deep or shallow—they can produce a potent toxin. Also called lockjaw, tetanus seriously affects the central nervous system and can be fatal.
Onset of symptoms can occur anytime from three days to three weeks. Call your health care provider if you have an open wound, particularly if:
Adults should have a tetanus booster shot every 10 years, known as the Td vaccine. It is a "2-in-1" vaccine that protects against tetanus and diphtheria. It contains a slightly different dose of diphtheria vaccine than what you received as a child. It can be given to anyone older than 7 years and is injected, usually into the arm.
Instead of the standard Td booster every 10 years, adults between the ages of 19 and 65 should receive Tdap one time in their adulthood to boost the immune system for pertussis, as well as tetanus and diphtheria.
Diphtheria, a contagious bacterial infection created that causes severe inflammation of the throat and larynx and can also affect the whole body. Pertussis or “whooping cough” is a serious bacterial infection that afflicted children and infants before vaccines were available. Adults may be infected later in life as their immunities wane. Neither of these infections are related to tetanus, but both vaccines are compatible and convenient to use with the tetanus booster.
