Disease Control Bulletin: May 2001
- West Nile Virus Update
- West Nile Virus Fact Sheet
- Preventing West Nile Virus
- Arthritis in Vermont
- Lead Poisoning in Vermont
- Common Insect Repellents and Mosquito Control Products
- Selected Reportable Diseases 1/1/2002–4/28/2001
- Characteristics of West Nile Virus
West Nile Virus Update
In 1999, an outbreak of West Nile virus in the New York City metropolitan area resulted in 62 hospitalized patients and eight deaths. In addition, 25 horses, 194 dead birds, and nine mosquito pools tested positive for the virus. While all of the human cases occurred in New York and New Jersey, Con-necticut and Maryland (with one positive dead bird) were also affected by the outbreak.
The identification of West Nile virus-positive mosquitoes in New York City during the winter of 2000 indicated that it was possible for the virus to overwinter in adult mosquitoes. And, a red-tailed hawk that died in February 2000 tested positive, providing further evidence that virus activity might be detected again in the spring of 2000.
In 2000, a more widespread outbreak involving 12 states plus the District of Columbia was detected by increased surveillance efforts. Twenty-one people were hospitalized and 63 horses, 4304 dead birds (over 70 different species), and 480 mosquito pools (over 14 different species) tested positive for the virus. One bird found dead in southern Vermont in September 2000 tested positive for West Nile virus. It is likely that West Nile virus is in Vermont, because it has been documented in New York, Massachusetts, and New Hampshire.
This year, dead birds collected in four states have already tested positive for West Nile virus. And, the Centers for Disease Control and Prevention (CDC) expects the virus to spread geographically, reaching the West Coast states within the next five years. Representatives from 48 states attended a national planning meeting in February 2001 to review and revise the CDC’s Epidemic/Epizootic West Nile Virus in the United States: Guidelines for Surveillance, Prevention, and Control.
The Vermont departments of Health and Agriculture, Food and Markets have developed the Vermont West Nile Virus Surveillance and Response Plan, based on the CDC’s guidelines. Surveillance will be conducted in dead birds, mosquitoes, horses, and people. Arboviral illness is being added to the list of reportable diseases in the Communicable Disease Regulations. Reports should be made to the Epidemiology Field Unit, Vermont Department of Health, 1-800-420-4374 or 863-7240, including weekends.
Who should be tested?
Hospitalized patients with encephalitis, especially when associated with diffuse muscle weakness, meningitis of supected viral origin, or Guillain-Barre syndrome should be tested. Testing is not recommended for suspected cases based on mild illness, such as fever or headache, and recent mosquito bites. Levels of West Nile virus activity in the community would have to be very high (i.e., at least several confirmed cases of severe illness) for such symptoms to likely be due to West Nile virus infection. In addition, since people with mild illness will most likely recover completely, testing is not necessary for prognostication. Individuals should be advised to seek medical attention if more severe symptoms develop, such as confusion, severe muscle weakness, severe headache, stiff neck, or photophobia.
Specimen Collection and Transport
Acute and convalescent serum: 7-10 ml of blood should be collected in eithera red-top or tiger-top collection tube. CDC recommends that acute phase serum be collected on day 10 of illness, asa large majority of people infected with West Nile virus have detectable serum IgM antibody by the eighth day of illness. CDC also recommends that convalescent serum be collected on day 21 of illness, as most infected persons demonstrate long-lived serum IgG antibody by three weeks post infection. People whose acute phase serum tests negative for IgM antibody should have a convalescent phase specimen submitted for testing. Specimens should be centrifuged and 1-2 ml of serum submitted at refrigerated temperature to the Department of Health Laboratory. Specimens should be accompanied by a completed Micro 214 Request for Serological Examination for Bacterial, Fungal, Parasitic & Viral Agents and CDC History Form #50.34 (rev 11/90). Cerebrospinal fluid: 1-2 ml of cerebrospinal fluid (CSF) should be collected as early as possible in the first few days of illness. In most cases of encephalitis caused by West Nile virus, IgM antibody will almost always be detectable in CSF by the eighth day of illness and sometimes as early as the day of onset. IgG antibody in CSF often does not reach detectable levels and thus isa relatively insensitive indicator of infection. Specimens should be submitted frozen to the Department of Health Laboratory accompanied by a completed Micro 214 Request for Serological Examination for Bacterial, Fungal, Parasitic & Viral Agents and CDC History Form #50.34 (rev 11/90). If date of onset is not included, CDC will not perform testing.Forms and serology mailers can be obtained by contacting the laboratory at (800) 660-9997, extension 7560.
Common Insect Repellants and Mosquito Control Products
The Vermont West Nile Virus Surveillance and Response Plan emphasizes public education on elimination of mosquito breeding habitats and prevention measures to reduce the risk of human exposure to mosquitoes. If surveillance data indicate a significant risk to human health, larvicides and/or adulticides may be used for mosquito suppression.
Larvicides, used to control immature forms of mosquitoes, are applied to potential mosquito breeding sites such as still or stagnant waters, catch basins, and tidal marsh land, where few people are likely to come into contact with these products. Although ground or aerial application of adulticides increases the risk of human exposure, these products are applied in such small volumes that they are very unlikely to cause any adverse health effects. Some sensitive individuals, however, including people with chronic lung disease (especially asthma), people with CNS dysfunction, and those with sensitivities to particular pesticides, or other ingredients in the formulations, could experience temporary exacerbations of their conditions or other adverse reactions to even small amounts of these products. Insect repellents and other pesticides that can be used by non-licensed individuals may also cause adverse reactions, especially if used excessively or inappropriately.
Products Available to Consumers
DEET (N, N-diethyl-3-methylbenzamide). DEET is found in commercial insect repellants (e.g. Off, Cutter) and is registered for direct application to skin, clothing, tents, and screens. It should not be applied to children younger than3-years-old or to children’s bedding. Products containing DEET should be washed off skin and clothing when a person is indoors and prolonged or excessive use should be avoided. Concentration of DEET should be limited to 30 percent or less for adults and 10 percent or less for children.
Health effects: Rashes, blisters, skin and mucous membrane irritation, and numb or burning lips have occurred among people who applied products containing a high concentration (e.g. 50% or greater), or among those excessively exposed. Toxic encephalopathy and seizures have been associated with use in children, specifically in children with orni-thine transcarbamylase (OTC) enzyme deficiency. Subtle neu-rotoxicity in adults (e.g. insomnia, mood disturbances, impaired cognitive function) has been associated with extensive application.
Carcinogenicity: While data are limited, there is no evidence of carcinogenicity.
Mosquito Dunk. Mosquito dunk contains Bacillus thuringiensis var. israelensis (Bti),a naturally occurring bacterium that kills mosquito larvae. It is available in hardware stores.
Health Effects: There have been no reports of serious acute or chronic effects from inhalation or ingestion of exposed plants or drinking water. Mild skin and eye irritation might result from direct contact (wash thoroughly with water).
Carcinogenicity: While data are limited, there is no evidence of carcinogenicity.
Products That Must Be Professionally Applied
Larvicides. Larvicides are applied to still or stagnant waters that are potential mosquito breeding sites, such as storm drains, waste water treatment plants, and abandoned pools. Products include Bacillus thuringiensis var. israelensis (Bti) [VectoBac], Bacillus sphaericus (Bs) [VectoLex], and methoprene [Altosid]. Bti and Bs are biological pesticides; the active ingredient is a microorganism. Methoprene is a biochemical regulator that interferes with an insect’s life cycle by preventing it from reaching maturity.
Health Effects: Neither Bti nor Bs is associated with serious acute or chronic health effects. Direct contact with skin and eyes can cause irritation. Methoprene has a very low potential for acute oral and inhalation toxicity, and is not an eye or skin irritant.
Carcinogenicity: There is no evidence that Bti, Bs, or methoprene are carcinogenic.
Adulticides. Adulticides are applied in very small volumes by ground or aerial spraying to control adult mosquitoes. Adulticides are not applied directly to water. Pyrethroids, a common type of adulticide, are synthetic pesticides similar to a natural pesticide (pyrethrum) produced by chrysanthemum flowers. Permethrin and resmethrin are pyrethroids. Pyrethroids can also contain petroleum solvents and piperonyl butoxide.
Health Effects: Pyrethroids can be inhaled, ingested, or absorbed through skin. Resmethrin has very low toxicity to humans. Permethrin is a non-toxic to moderately toxic pesticide, depending on the formulation. Short-term effects in sensitive individuals include eye, skin, nose and throat irritation, or breathing problems. Signs and symptoms of poisoning due to very high exposure include abnormal facial sensation, dizziness, salivation, headache, fatigue, vomiting, diarrhea, and irritability to sound and touch. Pulmonary edema, seizures, and fasciculations may occur in more severe cases. Pyrethroids do not cause cholinesterase inhibition.
Piperonyl butoxide is added to pyrethroid formulations to enhance insecticidal activity. It has limited dermal absorption on contact and is minimally toxic. Minor eye irritation may occur. Acute oral or dermal exposure is unlikely to result in systemic toxicity or dermal irritation.
Carcinogenicity: Laboratory studies have shown no evidence of carcinogenicity for resmethrin. There is inadequate evidence to assess the carcinogenicity of permethrin in animals. While laboratory animal studies of piperonyl butoxide have indicated the potential for hepatocellular tumors, testing of products that contain piperonyl butoxide have not indicated carcinogenicity in humans.
The New York City Department of Health. A West Nile Virus Supplement. City Health Information, June 2000.
Arthritis in Vermont
Arthritis is a term that refers to more than 100 conditions, each with its own distinct symptoms and associated treatments. It is a leading cause of disability in the United States. It directly affects nearly one in every six Americans; this is expected to increase to one in five by 2020.1 Nationally, the economic burden of arthritis is estimated at $65 billion annually, with $15 billion related to medical care costs and the remainder due to indirect costs such as lost productivity and disability compensation.2
Prevalence in Vermont
In 2000, an estimated 97,000 Vermonters were diagnosed with arthritis and an estimated 62,000 men and women reported activity limitations due to joint symptoms. Weighted estimates from arthritis-related questions on the 2000 Adult Behavioral Risk Factor Surveillance Survey show that in Vermont all age groups are affected by arthritis, and the prevalence of arthritis increases with age. In addition,a higher percentage of women reporta diagnosis of arthritis than men.
|Sex||Age||Ever Diagnosed with Arthritis||Chronic Joint Symptoms*|
Source: 2000 VT Behavioral Risk Factor Surveillance System
*Chronic Joint Symptoms are defined as symptoms present on most days for at least one month among respondents who answered “yes” to having joint paint in the past 12 months.
The most common types of arthritis reported by Vermonters were osteo/degenerative arthritis (36%) and rheumatoid arthritis (13.2%). Yet, over one-third of Vermonters reporting arthritis did not know their type of arthritis.
In 1999, an estimated 70 percent of Vermonters diagnosed with arthritis were not being treated.4 Men were significantly less likely to seek treatment than women after diagnosis of arthritis (4.0 percent vs.8.5 percent, respectively). Men were also significantly less knowledgeable about their condition; they were only two-thirds as likely as women to know their type of arthritis.
During 1999 there were 1,667 arthritis hospitalizations3,4 (up 8.5 percent from the previous year) in Vermont, accounting for 2.8 percent of resident inpatient hospitalizations. These hospitalizations represent over $26 million in hospital charges for 1999 (an increase of nearly 10 percent from 1998).
Risk Factors for Arthritis
There are risk factors that are associated with an increased probability of developing arthritis. Some are classified as non-modifiable, such as being female, being older, or having a genetic predisposition. Other risk factors associated with an increased risk of developing arthritis are potentially amenable to change. These modifiable risk factors include obesity, joint injuries, infections, and certain occupational exposures such as farming and working in the granite industry.
There is convincing evidence demonstrating that obesity hasa causal role in the development of osteoarthritis of the knee; there exists a 2- to4-fold increased risk of developing osteoarthritis in obese individuals [body mass index (BMI) > 30.0] compared to healthy weight individuals [BMI< 25.0].5 By reducing obesity through proper nutrition and regular physical activity, pain and disability associated with certain types of arthritis may be alleviated. In 2000, the percentage of adult Vermonters who were overweight/obese [BMI >25.0] was 61.4 percent for men and 44.3 percent for women.6 Additionally, only one quarter of adult Vermonters reported regular physical activity on at least five days per week for 30 minutes per session.
For more information about arthritis in Vermont, including self-management courses, contact the Northern New England Chapter of the Arthritis Foundation at (802) 864-4988, website: www.arthritis.org. Additional information is available at the Vermont Department of Health website: www.state.vt.us/_hs/epidemiology/arthritis/ arthritis.htm.
- CDC. Health-Related Quality of Life Among Adults with Arthritis- Behavioral Risk Factor Surveillance System, 11 States, 1996-1998. MMWR 2000; 49:366-369.
- Arthritis Foundation, Association of State and Territorial Health Officials, and CDC. National Arthritis Action Plan:a public health strategy. Atlanta, Georgia: Arthritis Foundation, 1999.
- ICD-9CM codes used to determine‘arthritis hospitalizations’ were set by the National Arthritis Data Workgroup in 1995 (see Arth Care Res (4); 1995: 203-211; MMWR June 1994; 433-438).
- Vermont 1999 Hospital Discharge Dataset.
- Brownson RC, Remington PL, Davis JR (Eds.). Chronic Disease Epidemiology and Control. 2nd ed. Washington, D.C.: American Public Health Association, 1998, pg. 469, 470.
- 2000 Vermont Behavioral Risk Factor Surveillance System.
Lead Poisoning in Vermont
Since 1993, the Vermont Department of Health, the Vermont Housing and Conservation Board, the Vermont Legislature, local health care providers, and the Vermont Chapter of the American Academy of Pediatrics have been working together to reduce the number of children affected by lead poisoning through blood lead testing, and primary and secondary prevention activities.
Blood Lead Testing
While the number of Vermont children screened for blood lead under age 6 has remained fairly constant since 1995, the percentage of 1-year-olds tested has increased from 27 percent in 1994 to 69 percent in 2000.
Following the Center for Disease Controls recommendation that all children be screened for lead poisoning at age 1, the Vermont Department of Health established the Lead Screening Advisory Committee which includes members of health care groups, state government, parent advocacy groups, and insurance organizations. Because health care providers had indicated that the extended finger/ heel wash cleaning portion of the capillary screening protocol was a barrier to in-office lead testing, the committee recommended that the Health Department conduct a study to evaluatea modified cleaning process.
In 2000, six Health Department district offices and five health care providers took part in the study. The results showed no significant difference in the number of false positives using either the abridged method of cleaning or the original two-minute finger/heel cleaning and that the modified cleaning was nota deterrent to in-office testing.
In the spring of 2000, the Health Department revised the blood lead screening guidelines to require screening at ages 1 and 2. The new guidelines have been distributed through the 12 Health Department district offices to approximately 1,000 health care providers in the Health Screening for Children and Adolescent Provider Toolkit. Further information will be available at the AAP spring meeting and at the June 27 telemedicine pediatrics grand rounds.
Over the next year, the Health Department will implement targeted screening strategies directed at parents of1 and2-year-olds with Medicaid and Dr. Dynasaur health insurance. The federal strategy to eliminate childhood lead poisoning also includes efforts directed at this high-risk population.
Primary Prevention Activities
Reducing a child’s exposure to lead hazards is the most effective way to reduce the incidence of childhood lead poisoning. In 1996, Vermont passed a law designed to reduce lead paint hazards in childrens’ environments. Act 165 requires all owners of rental housing and child care centers built before 1978 to performa series of essential maintenance practices (EMPs). Since 1996, more than 8,000 people have completed EMP training on safe maintenance and repair of painted surfaces. In addition, the department provides training to hardware store employees and they are encouraged to distribute lead information to customers.
Surveillance and Secondary Prevention Activities
All blood lead results are reported directly to the Health Department by the analytical laboratory and are entered into a lead poisoning database. As of December 2000, the lead database contained 53,716 blood lead results representing 38,688 Vermont children. The percentage of children with elevated blood lead levels has shown a steady decline from 11.7 percent in 1995 to 6.3 percent in 2000.
Depending on the child’s blood lead result, the Health Department offers the following services:
- 10- 14 µg/dl (capillary or venous)- Parents receive written information on reducing lead exposure and are asked to completea survey that provides data on the housing stock, hobbies, occupations, and other relevant demographics.
- 15- 19 µg/dl (venous)- The parents are offered all of the above and a home visit. The visit includes information on nutrition, housekeeping, and follow-up blood testing. If a child hasa consecutive blood lead result in this range, environmental testing takes place at the home.
- 20+ µg/dl (venous)- The parents are offered all of the above and a complete environmental investigation of the home. If the family lives in rental housing, the department will work with the property owner to ensure that lead hazards are reduced. If the family owns the home, staff will provide technical assistance on ways of reducing lead hazards.
In addition, the Vermont Housing Conservation Board, which receives funding from the US Department of Housing and Urban Development (HUD), helps property owners to reduce lead hazards. This board provides funding and management of lead hazard reduction work for eligible property owners.
For further information on lead poisoning prevention activities, contact Sheri Lynn or Laurie Toof at the Vermont Department of Health, PO Box 70, Burlington, VT 05402 (800)439-8550 (toll free in VT).
West Nile Virus Fact Sheet
What is West Nile virus encephalitis?
West Nile virus encephalitis is an infection of the brain caused by the West Nile virus. West Nile virus first appeared in the United States in 1999, when at least 62 people in the New York City area got sick and seven people died.
How do people get West Nile virus encephalitis?
People get it from the bite of an infected mosquito. Mosquitos are infected when they feed on an infected bird. When an infected mosquito bites a person, the virus is injected into the person and may cause illness. West Nile virus encephalitis is NOT spread from person to person.
Can people get West Nile virus encephalitis from birds?
There is no evidence that a person can get the virus from handling live or dead birds. However, wear gloves whenever handling a dead animal, including birds.
What are the symptoms of West Nile virus encephalitis?
Most cases are mild. Symptoms may include fever, headache, bodyaches, skinrash, and swollen lymph glands. More severe cases can cause headache, highfever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, paralysis, and rarely, death.
Who is at greatest risk of becoming ill from West Nile virus?
People over age 50 have the highest risk of getting severely ill if bitten by a mosquito infected with West Nile virus. Infants may also be at increased risk.
How is West Nile virus encephalitis treated?
There is no specific treatment for West Nile virus encephalitis, but the symptoms can be treated. In severe cases, hospitalization and treatment in an intensive care unit maybe required.
How common is West Nile virus in Vermont?
There have been no documented cases of human illness caused by West Nile virus in Vermont. However, a dead bird infected with the virus was found in Vermont in 2000. West Nile virus has been detected in mosquitos, horses, and/or birds in several surrounding states including New York, New Hampshire, Connecticut, and Massachusetts.
If a mosquito bites me, will I get sick?
Most mosquitos are NOT infected with West Nile virus. Even if an infected mosquito bites you, your chances of getting sick are low. However, you should see a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, or severe headaches.
Preventing West Nile Virus
What can I do to protect myself from West Nile Virus encephalitis?
You can begin by taking steps to reduce mosquito breeding areas near your home and bypreventing mosquito bites.
What can I do to keep mosquitos from biting?
- Wear long-sleeved shirts and long pants when you are outdoors.
- You may want to limit the amount of time you spend outdoors at dawn and dusk, or at other times when mosquitos are active.
- Use insect repellent that contains DEET (N,N-diethyl-meta-toluamide). Be sure to carefully follow the directions on the label. DEET can be harmful if overused. It should be applied sparingly, to clothing and exposed areas of skin. It should not be applied to a child’s face or hands, or to skin that is scratched or irritated. Use DEET repellents with concentrations below 10 percent for children and below 30 percent for adults. Do not use DEET on infants. Do not use DEET on children under age 3 or in concentrations greater than listed above, without first consulting your healthcare provider. Cream, lotion, or stick formulas are best for applying to areas of exposed skin. Wash skin where DEET was applied when mosquito exposure has ended.
- Take special care to cover up the arms and legs of children playing outdoors.
- Cover baby carriages or outdoor playpens with mosquito netting.
- Fix any holes in your screens and make sure they are tightly attached to the doors and windows.
What can I do to reduce the number of mosquitos around my home?
Mosquitos need water to reproduce. They can breed in any puddle or standing water that lasts more than four days. By removing areas of standing water around your house, you will eliminate their breeding grounds and reduce the number of mosquitos.
- Dispose of, or regularly empty, any metal cans, plastic containers, ceramic pots,and other water holding containers (including trash cans) on your property.
- Pay special attention to discarded tires. Tires are a common place for mosquitos to breed.
- Drill holes in the bottom of recycling containers that are left outdoors,so water can drain out.
- Clean clogged roof gutters of leaves and debris that prevent drainage of rainwater.
- Turn over plastic wading pools and wheelbarrows when not in use.
- Do not allow water to stagnate in birdbaths. Change it every three or four days.
- Aerate ornamental ponds or stock them with fish.
- Keep swimming pools clean and properly chlorinated. Remove standing water from pool covers.
- Use landscaping to eliminate standing water that collects on your property.
Vermont: Selected Reportable Diseases January 1, 2001 - April 28, 2001
Number of Cases
The Department of Health is pleased to welcome Ann R. Fingar, MD, MPH, as State Epidemiologist. Dr. Fingar has professional experience in the field of epidemiology at both the Illinois and Ohio state departments of health and taught preventive medicine and public health at the Ohio University College of Osteopathic Medicine. Prior to her work in public health, Dr. Fingar worked in clinical practice.
Peter Galbraith, DMD, MPH, retired from the position of State Epidemiologist on February 9, 2001. Dr. Galbraith’s tireless efforts on behalf of public health in Vermont during his four years in this position were and continue to be greatly appreciated.
Characteristics of West Nile Virus Disease
Infectious agent. West Nile virus is a member of the family Flaviviridae. It belongs to the Japanese encephalitis complex (including West Nile, St. Louis encephalitis, Japa-nese encephalitis, Murray Valley, and Kunjin).
Occurrence. Before the 1999 New York outbreak, West Nile virus had not been detected in the Western Hemisphere. Outbreaks of West Nile encephalitis had been identified only in Africa, Asia, the Middle East, and rarely, Europe. Seroprevalence rates in endemic areas overseas have ranged from 10 to 50 percent. A 1999 serosurvey of residents in the most affected area of New York City indicateda seroprevalence of about2.6 percent.
Reservoir and mode of transmission. Wild birds are the primary reservoir hosts and infected mosquitoes are the only known vectors. Ticks infected with West Nile virus have been found in Asia and Africa, but their role in the transmission and maintenance of the virus is uncertain. Humans and other animals can be infected incidentally, but are not involved in the normal transmission cycle. Neither person-to-person nor bird-to-person transmission is known to occur.
Incubation period. Usually6 days (range,3 to 15 days). Symptoms. Most people infected with West Nile virus have no symptoms of illness. Based on preliminary evidence, about one in four infected persons will have mild illness characterized by fever, headache, myalgias, arthralgias, lymphadenopathy, and a maculopapular or roseolar rash affecting the trunk and extremities. Pancreatitis, hepatitis, and myocarditis have occasionally been reported. More severe illness such as encephalitis or meningitis is less common and may be marked by high fever, muscle weakness, headache, stiff neck, stupor, disorientation, coma, tremors, convulsions, paralysis, and death. West Nile virus, because it can cause flaccid paralysis and axonal neuropathy on electromyographic testing, may be mistaken for Guillain-Barre syndrome. People age 50 and older have higher risk of severe illness.
Treatment. There is currently no known effective antiviral therapy or vaccine. Milder illnesses do not require therapy. In more severe cases, intensive supportive therapy such as intravenous fluids, airway management, respiratory support, and prevention of secondary infections, is indicated.
The New York City Department of Health. West Nile Virus: A Briefing. City Health Information, Vol. 19, No. 1, May 2000.
REPORT DISEASE : VERMONT TOLL-FREE
1-800-640-4374 OR 1-802-863-7240
Vermont Department of Health
Division of Health Surveillance P.O. Box 70 Burlington, VT 05402-0070
Agency of Human Services
Jan K. Carney, MD, MPH
THIS BULLETIN IS PRODUCED BY THE EPIDEMIOLOGY PROGRAM STAFF.
Ann R. Fingar, MD, MPH