Press Releases

2003 Releases

Many Americans in High-Mosquito Areas Think Their Family Likely to Get West Nile Virus Within Next 12 Months

For immediate release:  January 13, 2003

BOSTON, MA — A new study by Harvard School of Public Health researchers suggests that a substantial number of people in high-mosquito areas of the United States will feel threatened by the West Nile virus next summer. The opening study of the Project on Biological Security and the Public  finds that one-third (33%) of Americans who live in areas where there are a lot of mosquitoes think they or a family member is very (9%) or somewhat (24%) likely to get sick from the virus in the next 12 months. In addition, 32% of dog owners in high-mosquito areas are concerned that their dog might get the West Nile virus.

In those high-mosquito areas where there has been special spraying against mosquitoes to prevent the spread of the West Nile virus, nine in ten (91%) approve of the spraying. Nationwide, three-fourths (77%) of Americans said they would favor special spraying to prevent the spread of West Nile if it appeared in their area.

"The public has become sufficiently concerned about the West Nile virus that they are willing to take some risk on mosquito spraying, a controversial issue in many areas," said Robert J. Blendon, professor of Health Policy and Political Analysis at the Harvard School of Public Health. Some groups have protested against spraying, arguing that it aggravates respiratory problems and can cause environmental damage.

The findings were based on interviews with 1,001 Americans nationwide, including 516 who said there are a lot of mosquitoes where they live. Some 3,955 human cases of illness from West Nile have been reported, resulting in 252 deaths (as of January 8, 2003).

Precautions against Mosquito Bites

In high-mosquito areas, more than four in ten respondents (43%) report not having taken any precautions against mosquito bites during the past summer. Given the number of cases of West Nile, a virus that is mainly transmitted by mosquito bites, this finding raises an important public health concern.

The Centers for Disease Control and Prevention (CDC) recommend using mosquito repellant containing DEET, but only 43% of Americans living in high-mosquito areas say they used such a repellant (including the brands Off and Cutter) during the past summer. Three in ten (30%) used a mosquito repellant containing citronella, and 13% report using some other kind of mosquito repellant.

Fewer than half of Americans living in high-mosquito areas report that they took each of four other specific CDC-recommended precautions during the past summer. Four in ten (41%) report having removed standing water from spare tires, gutters, bird baths, kiddie pools, and other places where water collects. About one-third say they avoided going outdoors at the peak mosquito hours of dawn and dusk (32%) or wore long-sleeve shirts and other protective clothing outdoors (30%) during the past summer. One in five (20%) report having replaced or repaired window screens.

Much smaller numbers report having taken other precautions, such as using a “bug zapper” in their yard (7%) or buying mosquito netting (4%). Neither precaution has been recommended by the CDC.

The researchers could not conclude from the study results whether or not these precautions were taken specifically to protect against getting the West Nile virus. In high-mosquito areas, it is difficult to separate general precautions against mosquitoes from those aimed at dealing with a specific mosquito-borne threat. Many people living in high-mosquito areas, in order to prevent the annoyance of mosquito bites and probably aware of other dangers such as encephalitis, would take precautions in any case.

Not surprisingly, far fewer residents of areas where there are not very many mosquitoes took precautions against bites (33%, compared with 57% in high-mosquito areas). No more than one in five took any of the individual precautions, including using mosquito repellants that contain DEET (19%).

(For information about preventive measures, go to the CDC web site)

Public Knowledge and Beliefs about the West Nile Virus

Most residents of high-mosquito areas (83%) believe that recent cases of West Nile virus have happened naturally, rather than as the result of a terrorist attack (10%). Among all adults nationwide, three-fourths (78%) believe they have occurred naturally, while 12% think they are the result of bioterrorism.

The vast majority of residents of high-mosquito areas is aware that you can contract the West Nile virus from mosquito bites (96%). Of interest after media reports about cases where the West Nile virus was transmitted by blood transfusions and organ transplants, majorities of high-mosquito area residents know that the virus can be transmitted in these ways: 77% by blood transfusions, 62% by organ transplants.

However, half of high-mosquito area residents mistakenly believe that people can contract West Nile from contact with dead birds (54%) and drinking infected water (52%).

Only about one in 10 residents of high-mosquito areas believe, mistakenly, that you can contract the virus from shaking hands with (10%) or being in the same room (8%) as someone who has an active case of West Nile.

Only one in three residents of high-mosquito areas know that there is not an effective treatment for people who have contracted West Nile. About one-third overestimate how many people who get sick from the West Nile virus die: 19% believe one in four die and 14% think one-half do. According to CDC figures for 2002, 6% of those who got sick from the virus died.

Talking with Health Professionals, the Health Department, and Veterinarians

Only 6% of Americans who live in high-mosquito areas report having talked with their doctor or other health professional about the prevention or treatment of the West Nile virus during the past 12 months. During the same period, 3% have called their state or local health department or other government agency about preventing the spread of the virus. While these percentages are currently quite small, they could represent a serious strain on the health care and public health system in areas where cases are actually reported.

In high-mosquito areas, 13% of dog, cat, and horse owners report that they or someone in their household has at some time (not just in the past 12 months) talked with a veterinarian about how to protect their animal against West Nile virus. One-third of dog owners (32%) and 19% of cat owners say they are concerned that their animal might get West Nile virus.

This study was designed and analyzed by researchers at the Harvard School of Public Health. The project director is Robert J. Blendon of the Harvard School of Public Health. The research team also includes John M. Benson, Catherine M. DesRoches, Elizabeth Mackie, and Kathleen Weldon of the Harvard School of Public Health and Melissa J. Herrmann of ICR/International Communications Research. Fieldwork was conducted via telephone for the Project by ICR/International Communications Research of Media (PA) between November 8 and November 12, 2002. The project was funded through the federally-supported Center for Public Health Preparedness at HSPH.

For the full report, charts and methodology see:

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Robin Herman
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