Disease Control Bulletin: September 1998

Contents

disease control bulletin

Sept/Oct 1998

Influenza Update

Influenza and Pneumococcal Vaccination in Vermont

Vermont has made considerable progress in increasing the number of older Vermonters receiving influenza and pneumococcal vaccination.The Healthy People 2000 National Health Promotion and Disease Prevention Objectives call for vaccinating at least 60 percent of community residents who are at risk for influenza and pneumococcal disease. This includes all individuals ages 65 and older. Both of these vaccines are Medicare reimbursable.

The Vermont Behavioral Risk Factor Surveillance System (BRFSS) interviews non-institutionalized Vermont adults regarding multiple health behaviors. Each month, telephone calls are made to randomly selected households. Information is collected through a telephone survey with a standardized sample selection procedure and uniform set of questions. Every two years, those ages 65 and older are questioned regarding immunizations. The graph below illustrates the increases seen for both immunization levels since 1993. According to the 1997 BRFS Ssurvey, 69.6 percent of those > 65 who were interviewed reported having had a flu shot within the last 12 months, surpassing the Year 2000 goal. Even greater progress has been made for pneumococcal vaccine (PV) coverage. When asked if they had “ever had a pneumonia vaccination,” 52 percent responded positively. While Vermont still has not met the Year 2000 pneumococcal vaccine goal, the improvement is significant. However, among those > 65 who reported never having PV, 75 percent reported having had a routine physical in the past 12 months, suggesting a missed opportunity for providing this immunization.

For institutionalized chronically ill or older people, the Year 2000 goal is 80 percent vaccinated with PV and yearly influenza vaccine. The Health Department surveys the state’s long-term care facilities (LTCF) every two years regarding vaccination levels. Summaries of the last survey, completed for the winter of 1996-97, indicated that the average annual percentage of nursing home residents who received their annual influenza vaccine was 87 percent. Questions regarding pneumococcal vaccination were asked for the first time in 1996–97. Only 60 percent of responding LTCFs reported PV levels, with an average of 66 percent of residents having received PV.

Summary of Vermont’s 1997–98 Influenza Season: Ninety laboratory confirmed cases of influenza A and no cases of influenza B were detected in Vermont during last year’s influenza season. Cases were residents of 11 counties. Ages ranged from 8 months to 95 years, with a median of 71 years which was significantly higher than the previous year’s median age of 32. Forty-two (47%) of the confirmed cases last winter were residents of 12 nursing homes,compared to 11 (14%) cases in four facilities during the 1996-97 season.

senior vaccination percentage chart

Thirty-three of the positive viral cultures (36%) were identified as the H3N2 Sydney variant for which last year’s vaccine did not induce optimal immunity. Thirty-six cases (40%) are known to have received last season’s influenza vaccine. The fact that the Sydney strain was not a specific component of the 1997-98 vaccine may partially account for the heavy representation by long-term care facilities (LTCF) and the elderly among last winter’s confirmed cases. Vermont’s influenza data for last season were consistent with national findings with regard to peak activity, presence of the Sydney variant, and minimal influenza B activity.

InfluenzaA(H5N1): In May 1997, a 3-year-old child in Hong Kong developed an influenza-like illness (ILI) and died of complications including Reye syndrome. Influenza A (H5N1), a strain of the influenza virus that usually infects only birds, was isolated. This avian strain had not previously been known to infect humans. No additional cases were identified until November. When additional cases were suspected, teams from the Hong Kong Department of Health, the Centers for Disease Control and Prevention ( CDC), and the World Health Organization collaborated to investigate.By January 1998, 18 human cases of influenza A (H5N1) had been laboratory-confirmed. Six patients (33%) died.

Epidemiologic investigation determined that most of the influenza A (H5N1) human infections appeared to be acquired directly from chickens. While identification of this new strain in humans raised concerns that this virus could cause an influenza pandemic, the virus did not spread easily through person-to-person transmission, a characteristic associated with strains that become widespread. The CDC has worked with local health departments in several major U.S. cities to institute focused surveillance for the importation of influenza A (H5N1) among individuals with acute respiratory infections whose symptom onset was within 10 days of having been in Hong Kong or southernChina.NocaseswereidentifiedafterDecember,1997and all the human cases were identified in Hong Kong (1).

1998–99 Influenza Season: Summer outbreaks of influenza are uncommon in the United States, but early cases were documented between May and August this year, primarily among travelers to Alaska and the Yukon Territory. The isolates that have been strain typed were identified as the Sydney strain of influenza A which is included in this year’s vaccine.

Surveillance: Vermont participates in two forms of influenza surveillance, one active and one passive system. For many years a public health nurse in each Health Department district office has conducted telephone surveillance during influenza season, weekly contacting two local practices, the local hospital infection control practitioner, and a school nurse. The estimates of percent of patients with ILI from each setting are emailed to Burlington where the statewide data are summarized and a numeric value for Vermont’s influenza activity level is assigned and then relayed to CDC. The department appreciates the contributions of the many clinicians and their office staffs, infection control practitioners, and school nurses throughout Vermont who have participated in this effective and ongoing influenza surveillance system.

The second type of influenza surveillance is a sentine lsystem in which participating practices call CDC directly every week during the 34 week surveillance period to report their influenza data. Last year this was a CDC pilot project in 30 states and territories. The 10 Vermont practices that volunteered last year diligently recorded and regularly called in their influenza totals, helping to make the enhanced surveillance system so successful that it is now an established program.

Influenza testing: Diagnostic testing for influenza is available without charge to the submitter through the Vermont Department ofHealthLaboratory(VDHL). Testing is particularly important at the beginning and end of influenza season to document the presence of the disease in communities. Submission of specimens is also encouraged when ILI is noted in areas where it has not yet been documented during the season.

Influenza testing is crucial for documenting illness in institutional settings so that effective outbreak control measures can be implemented. Once influenza has been confirmed in a long-term care facility, a college dormitory, or other group facility, it is unnecessary to submit influenza specimens from additional symptomatic individuals during the same time period. Initially,as many as four to six specimens may be submitted.

After initial testing for influenza A and B, the VDHL will perform strain typing on all specimens positive for influenza. Strain typing on early and late season specimens are particularly helpful to establish whether this season's vaccine matches currently circulating strains.

The VDHL conducts two types of influenza testing—viral isolation on throat/naso-pharyngeal specimens and serology. Throat/naso-pharyngeal 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 specimen 14 days later. Contact the VDHL at 1-800-660-9997 or (802) 863-7335 to obtain specimen collection kits and for questions on collecting and shipping specimens.

Reference:

1. CDC/NCID. CDC team assists in investigation of avian flu outbreak in Hong Kong. Focus 1998;7:1-2

The Department of Health thanks the 1997–98 CDC Sentinel InfluenzaSurveillancePractices:

Robert W. Backus, MD, Townsend

David Coddaire, MD, Morrisville Family Health Care

Jack Mayer, MD & James Splain, MD, CHP Health Center, Middlebury The providers at The Health Center, Plainfield

Frank Meierdiercks, MD & Thomas Ziobrowski, MD at Church Street Internal Medicine, St. Johnsbury

Barbara Dalton, MD & Yolanda Lawrence, MD, Partners in FamilyMedicine,Springfield

Nancy Scattergood, MD, Bennington

Lynn Herzog, MD, CHP Pediatrics, Brattleboro Wendy Davis, MD, University Pediatrics (Burlington) Ann Wittpenn, MD, University Pediatrics (Williston)

TOP OF PAGE

Annual vaccination with inactivated influenza vaccine is considered the single most important measure to prevent or to lessen the severity of influenza infection

The optimal time for vaccination for persons in high-risk groupsisfromOctoberthroughmid-November.Vaccinationcan behighlycosteffectivewhenitisa)directedatthosewhoaremost likely to experience complications or who are at increased risk for exposure and b) administered to those at high risk during hospitalizations or routine health-care visits before the influenza season. This making special visits to physicians’ offices or clinics unnecessary.

The effectiveness of influenza vaccine in preventing or attenuating illness varies, in part depending on the degree of similarity between the virus strains included in the vaccine and those that circulate during the influenza season. When a good match exists, influenza vaccine has been shown to prevent illness in approximately 70 to 90 percent of healthy persons aged <65 years. The effectiveness of influenza vaccine in preventing hospitalizationforpneumoniaandinfluenzaamongelderlypersons who do not live in long term care facilities ranges from 30 to 70 percent. Among elderly persons residing in nursing homes, influenza vaccine can be 50 to 60 percent effective in preventing hospitalization and pneumonia and 80 percent effective in preventing death, even though efficacy in preventing influenza illness may range from 30 to 40 percent among the frail elderly.

The trivalent influenza vaccine prepared for the 1998–99 season will include A/Beijing/262/95-like (H1N1), A/Sydney/5/ 97-like(H3N2)andB/Beijing/184/93-like hemagglutinin antigens. For the B/Beijing/184/93-like antigen,U.S. manufacturers will use the antigenically equivalent strain B/Harbin/07/94.

Target groups for special vaccination programs

Groups at Increased Risk for Influenza-Related Complications:

Use of influenza vaccine during pregnancy: Case reports and limited studies suggest that pregnancy may increase the risk for serious medical complications of influenza as a result of increases in heart rate, stroke volume, and oxygen consumption; decreases in lung capacity; and changes in immunologic function. Pregnant women who have medical conditions that increase their risk for complications from influenza should be vaccinated before the influenza season, regardless of the stage of pregnancy. Studies of influenza vaccination of more than 2,000 pregnant women have demonstrated no adverse fetal effects associated with influenza vaccine; however, more data are needed. Because currently available influenza vaccine is not a live-virus vaccine and major systemic reactions to it are rare, many experts consider influenza vaccination safe during any stage of pregnancy. However, because spontaneous abortion is common in the first trimester and unnecessary exposures have traditionally been avoided during this time, some experts prefer influenza vaccination during the second trimester to avoid coincidental association of the vaccine with early pregnancy loss.

Groups that can transmit influenza to persons at high risk

Vaccination of other groups

Simultaneous administration of vaccines

The target groups for influenza and pneumococcal vaccination overlap considerably. For persons at high risk who have not previously been vaccinated with pneumococcal vaccine, health-care providers should strongly consider administering pneumococcal and influenza vaccines concurrently at different sites. Children at high risk for influenza-related complications can receive influenza vaccine at the same time they receive other routine vaccinations, including pertussis vaccine (DTaPorDTP). Because influenza vaccine can cause fever when administered to young children, DTaP (which is less frequently associated with fever and other adverse events than is DTP) is preferable.

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 prevention of influenza A in such persons. However, persons who have 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.

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

Antiviral agents for influenza A

The two antiviral agents with specific activity against influenza A viruses are amantadine hydrochloride and rimantadine hydrochloride. These chemically related drugs interfere with the replication cycle of type A (but not type B) influenza viruses. When administered prophylactically to healthy adults or children before and throughout the epidemic period, both drugs are approximately 70 to 90 percent effective in preventing illness caused by naturally occurring strains of type A influenza viruses. Because antiviral agents taken prophylactically can prevent illness but not subclinical infection, some persons who take these drugs can still develop immune responses that will protect them when they are exposed to antigenically related viruses in later years.

As with all drugs, amantadine and rimantadine can cause adverse reactions in some persons. Such adverse reactions rarely are severe; however, for some categories of patients, severe adverse reactions are more likely to occur. Amantadine has been associated with a higher incidence of central nervous system reactions than rimantadine.

Use of antivirals as prophylaxis

Chemoprophylaxis is not a substitute for vaccination. Recommendations for chemoprophylaxis are provided primarily to help health-care providers make decisions regarding persons who are at greatest risk for severe illness and complications if infected with influenza A virus.

When amantadine or rimantadine is administered as prophylaxis, factors such as cost, compliance, and potential side effects should be considered when determining the period of prophylaxis. To be maximally effective as prophylaxis, the drug must be taken each day for the duration of influenza activity in the community. However, to be most cost effective, amantadine or rimantadine prophylaxis should be taken only during the period of peak influenza activity in a community.

Prophylaxis may be considered for:

Use of antivirals as therapy

When administered within 48 hours of illness onset, amantadine and rimantadine can reduce the severity and shorten the duration of influenza A illness among healthy adults. Whether antiviral therapy will prevent complications of influenza type A among person at high risk is unknown. Insufficient data exist to determine the efficacy of rimantadine treatment among children. Thus, rimantadine is currently only approved for prophylaxis, not treatment, in this age group.

Amantadine- and rimantadine-resistant influenza A viruses can emerge when either of these drugs are administered for treatment; amantadine-resistant strains are cross-resistant to rimantadine and vice versa. Both the frequency with which resistant viruses emerge and the extent of their transmission are unknown,butdataindicatethattheseamantadine-andrimantadine-resistant viruses are no more virulent or transmissible than amantadine- and rimantadine-sensitive viruses.

Persons who have influenza-like illness should avoid contact with uninfected persons as much as possible, regardless of whether they are being treated with amantadine or rimantadine. Persons who have influenza type A infection and who are treated with either drug can shed amantadine- or rimantadine- sensitive viruses early in the course of treatment, but can later shed drug-resistant viruses, especially after five to seven days of therapy. Such persons can benefit from therapy even when resistant viruses emerge; however, they also can transmit infections to other persons with whom they come in contact.

Because of the possible induction of amantadine or rimantadine resistance, treatment of persons who have influenza-like illness should be discontinued as soon as clinically warranted, generally after three to five days of treatment or within 24 to 48 hours after the disappearance of signs and symptoms. Laboratory isolation of influenza viruses obtained from persons who are receiving amantadine or rimantadine should be reported to CDC through state health departments, and the isolates should be sent to CDC for antiviral sensitivity testing.

Outbreak control in institutions

When confirmed or suspected outbreaks of influenza A occur in institutions that house persons at high risk, chemoprophylaxis should be started as early as possible to reduce the spread of the virus. Contingency planning is needed to ensure rapid administration of amantadine or rimantadine to residents. This planning should include preapproved medication orders or plans to obtain physicians’ orders on short notice. When used for outbreak control, the antiviral should be administered to all residents of the institution—regardless of whether they received influenza vaccine the previous fall. The drug should be continued for at least two weeks or until approximately one week after the end of the outbreak. The dosage for each resident should be determined after consulting the dosage recommendations and precautions and the manufacturer’s package insert. Chemoprophylaxis also can be offered to unvaccinated staff who provide care to persons at high risk. Prophylaxis should be considered for all employees, regardless of their vaccination status, if the outbreak is caused by avariant strain of influenza A that is not controlled by the vaccine.

Highlights from: CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1998;47 (No.RR-6). The complete document,includinginformationonsideeffects,druginteractions and dosages, can be obtained by calling the Health Department (802-863-7240 or 1-800-640-4374). The URL is <ftp:// ftp.cdc.gov/pub/Publications/mmwr/rr/rr4706.pdf>.

TOP OF PAGE

Selected Reportable Diseases Vermont, Year to Date (08/29/98)

selected reportable diseases 8/29/98

YTD=Year to Date Total

No 5-year median available: Cryptosporidiosis; E.coliO157:H7; Group A Strep, Invasive

TOP OF PAGE

Outbreaks of Pneumococcal Pneumonia
in Chronic-Care Facilities

Although uncommon, outbreaks of pneumococcal pneumonia with bacteremia have been reported by the CDC and state and local public health agencies in Massachusetts, Oklahoma and Maryland. Multidrug-resistant Streptococcus pneumoniae was isolated in the Oklahoma outbreak from six patients, and from 23 percent of asymptomatic residents and 3.8 percent of asymptomatic employees. Among the three reported outbreaks, the death rate among residents with pneumonia ranged from 20 to 28 percent. Fewer than 5 percent of residents that were age 65 or older had documentation of previous vaccination with pneumococcal vaccine. The serotypes associated with disease in each outbreak are included in the 23-valent pneumococcal vaccine. The recent emergence of antimicrobial resistance among S. pneumoniae reinforces the importance of pneumococcal vaccine use in accordance with ACIP guidelines, particularly among the institutionalized elderly. When eligible residents are uncertain about their vaccination history or the resident’s medical record is incomplete, vaccine should be administered.

Source: CDC. Outbreaks of Pneumococcal Pneumonia Among Unvaccinated Residents in Chronic Care Facilities. MMWR;1997:46:60-62.

TOP OF PAGE

Salmonella Typhimurium DT104

In May 1997, Vermont experienced an outbreak of Salmonella Typhimurium DT104 on a Franklin County dairy farm. The outbreak involved nine cases of human illness, as well as illness and death of cattle. Three additional sporadic human cases of DT104 were identified in 1997 and eight in 1998 as of September 1.

Salmonella enterica serotype Typhimurium definitive type 104 (DT104) is a strain of Salmonella Typhimurium that was first recognized in the United Kingdom in 1984. DT104 is the second most prevalent strain of Salmonella isolated from humans in England and Wales and is epidemic in cattle and other animals there. Salmonella Typhimurium has recently emerged as an animal pathogen and a foodborne pathogen of humans in the United States. Of particular concern is that DT104 isolates are frequently resistant to multiple antimicrobial agents. The antimicrobial resistance pattern (R-type) often demonstrated is ACSSuT (resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline). In the United States, DT104 R-type ACSSuT has been isolated from humans, poultry, swine, cattle, and other domestic and wild animals.

The case fatality rate in humans may be higher than with other Salmonella infections. United Kingdom studies indicate a high rate of hospitalization. In the U.S., S.TyphimuriumR-type ACSSuT infections are more likely to cause bacteremia and have been associated with longer hospital stays. The CDC listed S.

Typhimurium as the second most frequently reported serotype in 1996. Special antimicrobial resistance studies were conducted in 1980, 1985, 1990, and 1995 in which all Salmonella isolates from specific counties were submitted to CDC. The proportion of those R-type ACSSuT that were DT104 was 0 percent in 1980, 25 percent in 1985, 50 percent in 1990, and 85 percent in 1995. It is important to note that not all DT104 isolates are antimicrobial resistant, and not all antimicrobial resistant isolates of Salmonella are DT104.

Contaminated food items and direct contact with infected animals are risk factors for transmission. There are no unique control measures for control of DT104. Recommendations for farm workers and their families include:(1)don’tconsumeordistribute raw milk, (2) wash hands after handling animals or anything they have touched, and (3) keep food and drinks out of the barn or anywhere animals are housed. The Vermont Department of Agriculture, Food and Markets (802-828-2421) can provide information outlining good farm management practices to keep animals and people healthy.

To learn more about this organism, including descriptive data of cases and the exten to fillness in humans, the Health Department recommends heightened surveillance including culturing patients with diarrheal illness. Suspect cases should be reported to Epidemiology (802-863-7240 or 1-800-640-4374). The URL is <http://www.fsis.usda.gov/OPHS/stdt104.htm>.

TOP OF PAGE