Disease Control Bulletin: October 1999

Contents

disease control bulletin

Volume 1, Issue 5, 1999

Influenza 1999-2000 Season

The following report summarizes the highlights of the 1999 recommendations of the Advisory Committee on Immunization Practices(ACIP)(MMWR1999;48[No.RR-4]) for influenza.The complete document may be obtained by calling the Vermont Department of Health at 802-863-7240 or 1-800-640-4374(inVT), or by accessing the Centers for Disease Control and Prevention website at <www.cdc.gov/ncidod/diseases/flu/fluvirus.htm>.

Summary of Vermont’s 1998-99 Influenza Season

Vermont had 84 laboratory confirmed cases of influenza during the 1998-99 season. The first case was reported in early January1999ina29-year-old woman from Bennington County and was identified as influenza A. The season was characterized as a moderate one and was remarkable for having simultaneous influenza A and B activity from late January through March. Influenza sub-typing identified A/H3N2/Sydney/5/97-likeandB/Harbin/7/ 74,B/Beijing/184/93-like strains in the Vermont population. These strains were included in the 1998-99 vaccine. Widespread activity was reported from January 30, 1999 through March 6, 1999. The laboratory confirmed cases ranged in age from 2 months to 95 years with a median of 47 years. This differs from the previous season, which had a median age of 71 years, and no cases of influenza B identified. Outbreaks of influenza A were reported during the 1998-99 season from six long term care facilities, accounting for 21 percent of all reported cases.

1999-2000 Vaccine Components

The trivalent influenza vaccine prepared for the 1999-2000 season includes A/Beijing/262/95-like (H1N1), A/Sydney/5/97-like(H3N2),andB/Beijing/184/93-likeantigens.FortheB/Beijing/ 184/93-like antigen, U.S. manufacturers are using the antigenically equivalent B/Yamanashi/166/98 because of its growth properties and it is representative of currently circulating B viruses.

Recommendation Updates

Epidemics of influenza occur during the winter months nearly every year and are responsible for approximately 20,000 deaths per year in the United States. Influenza vaccine is the primary method for preventing influenza and its more severe complications.

Increasing vaccination coverage among the high-risk groups is now the highest priority for expanding influenza vaccine use. Despite the reported benefits, nationally less than 30 percent of persons under age 65 and at high risk for influenza-related complications are vaccinated each year.

Influenza vaccine is strongly recommended for any person aged 6 months or older who, because of age or underlying medical condition, is at increased risk for complications of influenza. In addition, health care workers and others (including household members) in close contact with persons in high-risk groups should be vaccinated to decrease the risk of transmitting infection to persons at high risk. Influenza vaccine also can be administered to any person aged at least 6 months who wishes to reduce the chance of becoming infected with influenza.

Target Groups for Vaccination:

Persons at High Risk for Influenza-Related Complications

Groups Who Can Transmit Influenza to Those at High Risk

Other Groups to Consider

Persons Who Should NOT Be Vaccinated

Inactivated influenza vaccine should not be administered to persons known to have anaphylactic hypersensitivity to eggs or to other components of the influenza vaccine without first consulting a physician. Use of an antiviral agent (amantadine or rimantadine) is an option for preventing influenza A among such persons. Persons with a history of anaphylactic hypersensitivity to vaccine components but who are also at high risk for complications of influenza can benefit from vaccine after appropriate allergy evaluation and desensitization.

Persons with acute febrile illness should not be vaccinated until their symptoms have abated. However, minor illnesses with or without fever do not contraindicate the use of influenza vaccine, particularly among children with mild upper respiratory tract infection or allergic rhinitis.

Evolving Developments of Potential New Vaccines

Intranasally administered, cold-adapted, live, attenuated, influenza vaccines (LAIVs) are being used in Russia and have been under development in the U.S. since the 1960s. The viruses in these vaccines replicate in the upper respiratory tract and elicit aspecificprotectiveimmuneresponse.LAIVsconsistoflivevirus strains that induce minimal symptoms (i.e., attenuated) and that replicate poorly at temperatures found in the lower respiratory tract(i.e.,temperaturesensitive). No study has directly compared the effectiveness or efficacy of trivalent inactivated vaccine and trivalentLAIV.

Antiviral Agents for Influenza

Antiviral drugs for influenza are an important adjunct to influenza vaccine for the control and prevention of influenza.The currently licensed agents are amantadine hydrochloride and rimantadine hydrochloride, which are chemically related antiviral drugs with specific activity against influenza A viruses but not influenza B viruses. Amantadine was approved in 1976 for the treatment and prophylaxis of influenza type A virus infections in adults and children age 1 year and older. Rimantadine was approved in 1993 for treatment and prophylaxis of infection in adults. Although rimantadine was approved only for prophylaxis of infection in children, many consider it appropriate for treatment among children. Amantadine and rimantadine differ in terms of pharmacokinetics, side effects, and costs. Rimantadine is associated with fewer central nervous system side effects than aman-tadine, but is more expensive.

Amantadine-resistant viruses are cross-resistant to rimantadine and vice versa. Drug resistant viruses can appear in up to approximately one third of patients when either amantadine or rimantadine is used for therapy. Amantadine-andrimantadine-resistant viruses are no more virulent or transmissible than sensitive viruses. The screening of epidemic strains of influenza A has rarely detected amantadine- and rimantadine-resistant vi-ruses. Persons who have influenza A infection and who aretreated with either drug can shed sensitive viruses early in the course of treatment and later shed drug-resistant viruses, especially after 5 to 7 days of therapy. Such persons can benefit from therapy even when resistant viruses emerge. Influenza isolates obtained from persons who are receiving amantadine or rimantadine should be reported to the Vermont Department of Health who will send the isolates to CDC for antiviral sensitivity testing.

Another class of influenza antiviral drugs, neuraminidase inhibitors, with activity against both influenza A and B is now available. Currently, Zanamivir (Relenza - Glaxo Wellcome), a neuraminidase inhibitor taken by inhalation, has been approved by the Food and Drug Administration for treatment of influenza. Oseltamivirphosphate(Tamiflu-Roche/Gilead;GS4104),anoral neuraminidase inhibitor, will probably be approved soon.

Influenza Testing

Diagnostic testing for influenza is available without charge to the submitter through the Vermont Department of Health Laboratory(VDHL). The VDHL conducts two types of influenza testing – viral isolation on throat/nasopharyngeal specimens and serology. Testing is particularly important at the beginning and end of influenza season to document the presence of disease in communities. Testing is also crucial in institutional settings so that effective outbreak control can be implemented. Once influenza has been confirmed in an institutional setting, it is no longer necessary to submit additional specimens from symptomatic individuals during the same time period.

After initial testing for influenza A and B, the VDHL will perform strain typing on all specimens positive for influenza. Throat/nasopharyngeal specimens are most accurate when collected within three days of symptom onset. Serology requires the collection of acute and convalescent specimens, the first within seven days of onset and the second 14 days later. Please contact the VDHL at 802-863-7335 or 1-800-660-9997 (in VT) to obtain specimen collection kits and for questions regarding collection and shipment of specimens.

Reporting

Both sporadic cases and clusters of confirmed or suspected influenza should be reported to Epidemiology at 802-863-7240 or 1-800-640-4374(inVT).

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Chronic Disease in Vermont: Asthma

Asthma in Children

Estimates of Vermont prevalence based on the 1995 National Health Interview Survey (NHIS) data give a prevalence for pediatric asthma of 75 per 1,000 (1). Nationally, the age group at highest risk of asthma (self-report) is the 5 to 14 year-old group with a prevalence of 74.4 per 1,000. In contrast, the 0 to 4 year-old age group has the fastest growing prevalence. The most substantial increase in prevalence occurred among children aged 0 to 4 years (160%, from 22.2 per 1,000 to 57.8 per 1,000;p<0.05) and those aged 5 to 14 years (74%, from 42.8 per 1,000 to 74.4 per 1,000;p<0.05)(2).

There were no deaths among Vermont children under age 15 yearsduringthetimeperiod1993-1997(3). Asthma was a leading reason for hospitalization among Vermont’s children from 1986-1995 (4). In children under age 15, Vermont asthma hospitalizations increased until 1995 when the rate plateaued (Figure 1). Young children, especially boys, and older adults, especially women, had the highest rates of asthma hospitalization (Figure2).

asthma discharge rates for vermont residents

Environmental risk factors for asthma(5) include house-dust mites in children’s beds (high exposure increases the risk of having asthma by age 11), indoor humidity, outdoor humidity, air exchange, pets (especially cats), amount of furnishings, and the regularity with which furnishings are laundered. The etiology of asthma has a possible genetic component as well as being influenced by immune-system factors and environmental exposures. Children at higher risk of developing asthma were more likely to be low birthweight babies, exposed to tobacco smoke in utero or in early life, sensitized to common allergens at an early age, or were not breastfed. Higher-risk children also had a low intake of omega3 fatty acid or anti-oxidant vitamins, a parent with asthma or allergic illness, or a serious respiratory infection in early life. Many risk factors for asthma are public health concerns in their own right.

Asthma in Adults

Estimates of Vermont prevalence based on 1995 NHIS data give a prevalence for adult (18+) asthma of 50 per 1,000(1). Crude preliminary data from the first five months of the 1999 Behavioral Risk Factor Surveillance Survey (BRFSS)(6) suggest prevalence may be higher for non-institutionalized Vermonters over age 18. The prevalence for adults reporting that they had ever had asthma was 113 per 1,000. Of those ever having asthma, 73 percent reported still having asthma, a rate of approximately 82 per 1,000.

asthma diagnoses for Vermont Residents

In the last 10 years, four to 13 Vermont residents died from asthmaeachyear.Theage-adjusted (7) mortality data for Vermont were very similar to the U.S. rate. The age-adjusted average rate for 1993 -1997 was 1.11 per 100,000 for both sexes. The age-adjusted U.S. rates for 1997 were 1.4 per 100,000 for all races and 1.1 per 100,000 for white race only (8).

In addition to the risk factors for asthma mentioned above, many adults may have occupational exposures. Occupational risk for asthma has been associated with specific exposures by animal handlers, veterinarians, laboratory workers, bakers, millers, chemical workers, coffee or tea workers, detergent workers, electronics workers, farm workers, fishery and oyster workers, grain handlers, insect handlers, hairdressers, leather workers, lumber and woodworkers, metal workers, paper product workers, pharmaceutical workers, plastic workers and automobile repair (9).

Conclusion

Secondary prevention for asthma includes the avoidance of asthma triggers, for example covering mattresses with occlusive covers, washing and replacing pillows regularly, avoiding tobacco smoke (or quitting smoking) and managing disease (including written treatment plans, monitoring peak flow, following treatment guidelines) to prevent needless morbidity. For more information, please contact the American Lung Association of Vermont at (802)863-6817 or 1-800-LUNG-USA.

References:

  1. American Lung Association. Estimated Prevalence and Incidence of Lung Disease by Lung Association Territory. 1999;(April):56.
  2. Mannino DM, Homa DM, Pertowski CA, et.al. Surveillance for asthma - United States, 1960-1995. MMWR 1998;47(SS-1):1-27.
  3. Vermont Vital Statistics Dataset.
  4. Brozicevic P, Baron K, Kahn D, Houston J. 1995 Vermont Hospital Monograph Companion. Montpelier, VT: Department of Banking, Insurance, Securities and Health Care Administration, 1999.
  5. Peat JK. Prevention of asthma. Eur Resp J 1996;9:1545-1555
  6. Vermont Behavioral Risk Factor Surveillance Survey.
  7. The age-adjustment standard was the U.S. 1970 standard population.
  8. Hoyert DL, Kochanek, KD, Murphy SL. Deaths: final data for 1997. Natl Vital Stat Rep 1999;47(19):65.
  9. From Table 9.4 in: Brownson RC, Remington PL, Davis, JR (eds). Chronic Disease Epidemiology and Control. Washington, D.C.: American Public Health Association, 1993. adapted from Alberts WM, Brooks SM. Advances in occupational asthma. Clin Chest Med 1992;13:281-302.

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Selected Reportable Diseases Vermont
Year to Date (10/02/99)

reportable diseases october 1999

YTD=YeartoDateTotal

No 5-year median available: Cryptosporidiosis; E. coli O157:H7; Group A Strep, Invasive; Acute Hepatitis C

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Call for Historical Articles

The January 2000 issue of the Disease Control Bulletin will focus on historical accounts of significant public health events in Vermont. This may include descriptions of disease outbreaks, special events, or milestones in public health. Anyone interested in contributing an article should contact Susan Schoenfeld at 863-7240 or 1-800-640-4374.

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Changes in Polio Vaccine Availability

The Vermont Department of Health (VDH) has been informed by the Centers for Disease Control and Prevention (CDC) that Wyeth-Lederle, manufacturer of live oral poliovirus vaccine (OPV), plans to discontinue their production of OPV. OPV will no longer be made available for public or private purchase. The CDC will keep a national stockpile of OPV that will be reserved for emergency purposes only.

Effective November 1, 1999, the VDH will supply inactivated poliovirus vaccine (IPV) for all four doses of the routine childhood vaccination schedule. OPV will continue to be made available, to those providers requesting it, until our supply is exhausted. We anticipate that may be as soon as January 2000. Please contact the VDH Immunization program with any questions regarding vaccine availability at 863-7638 or 1-800-464-4343. The recommendations of the Advisory Committee on Immunization Practices (ACIP) follow.

Revised Recommendations for Routine Poliomyelitis Vaccination, MMWR 1999;48:590

Since 1979, the only indigenous cases of poliomyelitis reported in the United States (n=144) have been associated with use of OPV (an additional six imported cases have been reported since 1979, the last of which occurred in 1993). Until recently, the benefits of OPV use (i.e., intestinal immunity, secondary spread) outweighed the risk for vaccine-associated paralytic polio (VAPP) (one case per 2.4 million doses distributed). In 1997, to decrease

the risk for VAPP while maintaining the benefits of OPV, the ACIP recommended a sequential schedule of IPV followed by OPV. Since 1997, the global polio eradication initiative has progressed rapidly, and the likelihood of poliovirus importation into the United States has decreased substantially. In addition, since 1997, the sequential schedule has been well accepted. No declines in vaccination coverage were observed, despite the need for additional injections.

On the basis of these data, on June 17, 1999, to eliminate the risk for VAPP, the ACIP recommended an all-IPV schedule for routine childhood polio vaccination in the United States. As of January 1, 2000, all children should receive four doses of IPV at ages 2 months, 4 months, 6 to 18 months, and 4 to 6 years. OPV should be used only for the following special circumstances:

  1. Mass vaccination campaigns to control outbreaks of paralytic polio.
  2. Unvaccinated children who will be traveling in less than four weeks to areas where polio is endemic.
  3. Children of parents who do not accept the recommended number of vaccine injections. These children may receive OPV only for the third or fourth dose or both; in this situation, health-care providers should administer OPV only after discussing the risk for VAPP with parents or caregivers.

ACIP reaffirms its support for the global polio eradication initiative and use of OPV as the vaccine of choice to eradicate polio from the remaining countries where polio is endemic.