Epidemiological Bulletin: Summer 2001 (Part 1 of 2)
Advisory on Salmonella in Cantaloupes
Beth Schulz, PHN, MPH (CD Control Officer)
Following a recent outbreak of Salmonella food- borne disease associated with eating cantaloupe in California and seven other states, the public is reminded to thoroughly wash the skin of all fruits and vegetables that are eaten raw before eating or slicing them, to wash hands thoroughly before and after handling the fruit and to refrigerate unused cut portions immediately.
California has recently had 19 cases of a rare strain of Salmonella poona through the third week of May 2001; no cases were reported in the state in 1998-2000. Cases primarily involved older adults (60-88 years old) and young children (1-5 years old) in southern California. Six patients had positive blood cultures and one case died. Thirteen other cases have been reported in seven other states in the same outbreak.
The source of contamination is under investigation and it is likely that the contaminated fruit was imported into the U.S. Cantaloupe has been implicated in previous Salmonella outbreaks. Because the fruit is grown on the ground, the skin can be contaminated in the field by human or animal waste, or during distribution prior to sale. Symptoms of salmonellosis include fever, abdominal cramps, and diarrhea, which occur 1-3 days after eating a contaminated food. While most individuals recover in 3-5 days, the infection can be life threatening to young children, the elderly, and the immuno- compromised.
Meningococcal Infections and Prevention, 2001
Gloria Tzuang, MPH (Epidemiologist) and Beth Schulz, PHN, MPH (CD Control Officer)
Despite heightened media coverage of cases of meningococcal disease that have occurred recently in Northern California, the number in California is within the typical range for the year. Approximately 400 cases of meningococcal disease are reported annually in California -- approximately 200 cases occur in children younger than 9 years old and 20-30 of these cases die, while about 50 cases occur in middle school- and high school-age children with approximately 5-10 fatal outcomes. In San Mateo County, an average of 7-11 cases of meningococcal disease are reported each year, including 2-4 deaths, usually in the winter and spring. This year, six cases have been reported to date, ranging in age from one month to 88 years old, with three deaths. None of the cases were epidemiologically linked.
Pathogenesis: Neisseria meningitidis is a gram- negative diplococcus that can be found in the nasopharyngeal passages of up to 40% of healthy individuals. There are 13 serogroups, which are differentiated by distinct capsular polysaccharides. Of these serogroups, eight are capable of causing human disease; and two, groups B and C, are the most common in the United States. Within each serogroup, there are unique strains. By definition, an outbreak occurs when multiple cases are caused by the same strain. The mechanisms by which the bacteria penetrate cells and cause disease is still unclear; but it is known that only unencapsulated meningococci are capable of entering cells. Research suggests that an individual is most likely to become ill when first exposed to a new strain of N. meningitidis. The carrier state induces strain-specific immunity, and thus carriers are protected against developing disease when exposed to the same emerging epidemic strains.
The two most common manifestations of meningococcal disease are meningitis and meningococcemia. Meningitis can also be caused by other pathogens, including viruses, Haemophilus influenza B, and Streptococcus pneumoniae. Because there are vaccines for the latter two (HIB and the new pneumococcal conjugate vaccine ("Prevnar" Ð see article on p. 4), while viral meningitis is usually less severe, N. meningitidis has become the most common and feared cause of meningitis.
Meningococcemia is a meningococcal infection in the blood, which has an even higher case fatality rate than meningitis. Patients often present with signs of sepsis, generalized myalgia, petechial lesions, and sometimes a transient maculopapular rash. Progression to death can be extremely rapid. Meningitis and meningococcemia can occur separately or concurrently.
Chemoprophylaxis: Chemoprophylaxis is indicated for close contacts of all persons with invasive meningococcal disease, including household members, individuals in child care centers and nursery schools, and persons directly exposed to oropharyngeal secretions through kissing or sharing of food or beverages during the 7 days before the onset of symptoms in the index case. Prophylaxis is not routinely recommended for medical personnel except for those with close unprotected contact with nasopharyngeal secretions (e.g. mouth-to-mouth resuscitation, intubation, or suctioning).
Chemoprophylaxis is most effective if given within 24 hours of case identification and is not of much value if > 14 days have elapsed, as most secondary cases occur several days following disease onset in the index case. For this reason, any meningococcal disease cases should be reported to the Disease Control and Prevention Unit immediately, so that control measures such as contact identification and chemoprophylaxis can be implemented.
Chemoprophylactic agents recommended for elimination of the carrier state include rifampin, ceftriaxone, or ciprofloxacin. Rifampin is given BID x 2 days and is 72-90% effective in eradicating nasopharyngeal carriage, although rapid emergence of resistant strains of Neisseria meningitidis following prophylaxis has been observed. Ceftriaxone is administered in a single IM dose and is > 95% effective in eradicating carriage. To reduce pain at the injection site, ceftriaxone should be diluted in 1% lidocaine. In non-pregnant adults, a single dose of ciprofloxacin is an effective (90-95%) oral alternative to rifampin. Although ciprofloxacin has been used in children for meningococcal chemoprophylaxis, it is not approved by the FDA for use in children < 18 years of age except following exposure to inhalation anthrax. Fluoroquinolones such as ciprofloxacin have caused cartilage damage in every juvenile animal model at therapeutic doses. Nonetheless, the AAP Red Book 2000 states that ciprofloxacin appears to be well tolerated in children, does not appear to cause arthropathy, and is effective as an oral agent for treating a number of diseases that would otherwise require parenteral therapy.
- A recent international consensus report has concluded that ciprofloxacin can be used for meningococcal chemoprophylaxis of children when no acceptable alternative is available.
- Ciprofloxacin has recently been used for prophylaxis of large populations of high school students 14-18 years old following multiple cases of meningococcal disease without apparent epidemiological links, where the benefits of using the medication outweigh the risks. A major advantage over other regimens includes the ability to directly observe administration of the single oral dose, thus ensuring high rates of compliance. It is also relatively inexpensive (about $1/dose) and accessible to public health departments, which commonly use it to treat gonococcal infections.
Vaccine: The quadrivalent A, C, Y, W-135 polysaccharide vaccine (Menomune) is the formulation currently available in the U.S. Current CDC guidelines suggest that routine vaccination of civilians is not recommended because of its relative ineffectiveness in children < 2 (the age group with the highest risk for sporadic disease) and because of its relatively short duration of protection. However, providers of care to incoming and current college freshman, particularly those who plan to or already live in dormitories and residence halls, should inform these students and their parents about the moderately increased risk of meningococcal disease in this age group/setting and the potential benefits of vaccination, and have the vaccine on hand to administer to these students who wish to be vaccinated.4 The vaccine is also routinely recommended for use persons with certain complement deficiencies, functional or anatomic asplenia, for travelers to countries where meningococcal disease is endemic or epidemic, and for control of outbreaks of serogroup C. Lastly, a conjugate serogroup C vaccine for infants has recently been introduced in the UK and should be coming to the US in the next several years. Research for vaccines effective against serogroup B continues in several countries and the US.
References 1. American Academy of Pediatrics. Pickering LK, ed. 2000 Red Book of the Committee on Infectious Diseases. 25 th ed. Elk Grove Village, IL. American Academy of Pediatrics; 2000.
2. Control and Prevention of Meningococcal Disease and Control and Prevention of Serogroup C Meningococcal Disease: Evaluation and Management of Suspected Outbreaks. MMWR February 14, 1997/vol.46/No. RR-5.
3. Apicella MA. Neisseria meningitidis. In Mandell GL, Bennet JE, Dolin R eds. Principles and Practice of Infectious Diseases. 5 th ed. Philadelphia: Churchill Livingstone;2000:2467.
4. www.cdc.gov/mmwr/PDF/rr/rr4907.pdf
Epidemiology of TB in San Mateo County
Scott Nabity, MPH (Epidemiologist)
This is the first in a series of articles dedicated to the epidemiology and control of TB in San Mateo County that will be published in the Epidemiology Bulletin.
Background: During the last 20 years, the burden of tuberculosis in San Mateo County has followed trends similar to those experienced in both California and the U.S. Despite previous decades of progress in reducing the burden of TB, local incidence began to rise in the mid-1980s and peaked in 1991 before eventually declining to near pre-epidemic levels in 2000 (Fig. 1). Within a period of only two years, the rate of TB more than doubled between 1985 (n=32 cases) and 1987 (n=66 cases). By 1991 (n=96 cases) the rate had tripled.
Clearly, great progress has been made both locally and nationally in reclaiming control in the battle against TB. Although not having yet achieved the Healthy People 2000 goal set by the CDC more than a decade ago, California, with a TB rate historically much higher than the national rate, achieved its 2000 goal of 10.0 cases per 100,000 population. San Mateo County reached this goal a year earlier, although reporting more cases (n=63 cases) in 1999 than 14 states.
Nationally, the epidemic of the late 1980s and 1990s was attributed to several factors, including increasing incidence in residents born in heavily endemic countries, and in those incarcerated or residing in other congregate institutional settings; a general reduction in the funding and infrastructure for TB control; and the growing number of people in the U.S. living with HIV. HIV infection is probably the most significant of the medical conditions that put individuals at risk for TB, potentially increasing risk by as much as 100 times that for the general population. This increased susceptibility translates into a 7-10% annual risk of developing TB for those infected with the TB mycobacyterium. Although San Francisco has seen a close association between the AIDS epidemic and an increase in TB cases, San Mateo County has a much lower rate of HIV-infection and AIDS, and sees very few cases of TB occurring in this population.
Tuberculosis Infection: A chronic, asymptomatic infection occurs in most people who become infected with the TB mycobacterium. Without treatment, 10% of those infected will develop TB disease at some point during their lifetime, with the highest risk occurring in the first two years after initial infection. Partially reflecting this lifetime risk, nearly 40% of TB cases were 55 years of age or older during 1993-2000, while children under 15 constituted less than 7% of the total (Fig. 2).
Fig. 2: TB Cases by Age Group
Because infection and disease in young children, particularly those born in the U.S., serve as useful indicators for recent transmission of TB, they are of special utility for public health surveillance. Since 1993, 70% of San Mateo cases less than 15 years of age were born in the U.S. (83% of cases less than 5 years of age). The temporal trend for this indicator closely follows the epidemic curve for all cases, supporting a point that may seem intuitive: transmission of TB to children was greatest when the overall local burden of TB was greatest. Cases less than 5 years of age were most frequently reported in 1992 and 1993 (Fig. 3).
Ethnic Demographics: Risk of TB infection varies widely in different ethnic populations (Fig. 4). While non-Hispanic whites made up over 50% of the average County population during 1995-2000, this population constituted little more than 10% of the TB cases during the same time period. Conversely, more than 60% of local cases reported from 1995-2000 were Asian or Pacific Islanders, whereas that population constituted only 20% of the County average population during the same period. Non-Hispanic whites, with a rate of 0.5 cases per 100,000 population, were the only racial and ethnic group to achieve the Healthy People 2000 goal by 2000.
While the proportion of cases that are Latino matches the proportion of County residents who are Latino, the rate of TB disease in this population was 9 times higher than for non-Hispanic whites in 2000, and the rate for the Asian and Pacific Islander population was 45 times higher. It is noteworthy that no cases were reported among African-Americans in 2000, although they represent about 5% of the County population. Encouragingly, this population has shown this marked decline in TB morbidity from a high of 52.7 cases per 100,000 in 1992.
The variances among racial and ethnic groups can largely be explained by the incidence of TB in immigrants from countries where TB is epidemic. In 1992, 62% of cases were foreign-born. This figure increased to 93.5% in 2000, reflecting among other things a decline in level of ongoing transmission of TB locally (Fig. 5). From 1993-2000, 481 (78.9%) of 610 cases reporting in San Mateo County were born outside the U.S. in locations ranked as follows: Philippines (53.0%); SE Asia and Pacific Islands not including the Philippines (16.6%); Mexico (13.3%); Latin America (9.6%); and 7.5% from other locations.
Resources and References
1. Healthy People 2000/2010 Websites (www.health.gov/healthypeople)
2. U.S. Department of Health and Human Services. (August 2000). Report on Tuberculosis in the US, 1999. (www.cdc.gov/nchstp/tb/surv/surv99/surv99.htm)
3. U.S. Department of Health and Human Services. (2000). Core Curriculum on Tuberculosis, 4th ed.
4. U.S. Department of Health and Human Services. (December 1992). 1993 Revised Classification System for HIV Infection and Expanded Surveillance Case Definition for AIDS Among Adolescents and Adults. Morbidity and Mortality Weekly Report, Vol. 41, No. RR-17.
Data Sources for Figures
TB Data: MMWR, CA DHS and San Mateo County Health Services, DCPU, Reports of Verified Case of Tuberculosis (RVCT).
Population Data: CA Dept. of Finance, Demographic Research Unit, State Population Estimates by Race, Age and Sex, 1970-2040 (pub. 1996.)
IZ Updates and a New Pneumococcal Vaccine
Sam Stebbins, MD, MPH (Deputy Health Officer)
In February 2000, a new 7-valent pneumococcal polysaccharide-protein conjugate vaccine (Prevnar) was licensed by the FDA. The CDC, AAP, and the AAFP have endorsed the use of this vaccine as part of the standard infant and child vaccination series. As antibiotic resistance in pneumococcal bacteria continues to increase, prevention becomes ever more important.
Each year in the United States, an estimated 1,400 cases of meningitis, 16,000 cases of bacteremia, and 5 million ear infections caused by pneumococcus occur among children under 5. Children less than two years of age have the highest risk of infection. About 10 percent of children who develop meningitis die, while up to 50 percent sustain brain damage and hearing loss. The PCV7 vaccine provides potential serotype and serogroup cross-protection for 88 percent of the cases of bacteremia, 82 percent of the cases of meningitis and 71 percent of the cases of pneumococcal otitis media episodes in U.S. children younger than six. The ACIP recommends immunization for all children under age two as per Table 6, next page, along with children 24-59 months old with the following high-risk conditions:
- Sickle Cell Disease and other sickle cell hemoglobinopathies
- Congenital, acquired, or functional asplenia
- HIV and other immunosuppressive conditions (including renal failure and nephrotic syndrome, cancer, organ transplantation, and congenital immunodeficiencies)
- Chronic illnesses, including diabetes, CSF leaks, cardiac conditions, and pulmonary (excluding asthma unless on high-dose steroid therapy)
All other children 24-59 months may be considered for vaccination, but priority should be given to those shown to be at moderately elevated risk of invasive disease: 1) children of Native American, Alaska Native, or African-American descent; 2) children in group child care (not kindergarten); and 3) all children 24-35 months. Administering PCV7 to children > 59 months of age with high-risk conditions is not contraindicated, but there is limited data on efficacy.
While the vaccine's safety profile appears very good, data so far does suggest that PCV7 may be among the most reactogenic vaccines of those currently available. Local reaction may occur in up to 30% of patients and fever in 10%, so make sure to alert your staff and parents. Studies do not show an increase in reaction with subsequent doses. In terms of efficacy, when given at two, four, six, and 12 to 15 months of age, PCV7 induces good antibody response in infants. After three doses, 92 to 100 percent of children had at least 0.15 mg per mL of antibody against all seven of the vaccine serotypes, and 51 to 90 percent of the children reached a level of at least 1.0 µg per ml against the seven vaccine serotypes. Administration of the fourth dose results in a prompt increase in antibody levels to all seven serotypes.
PCV7 Reimbursement: As to reimbursement, the VFC program provides vaccine for CHDP kids, but CHDP does not currently reimburse for administrative costs of this vaccine. Providers have the option of billing CHDP patients up to $17.55 per dose, but may not withhold vaccine for VFC-eligible kids based on inability to pay. For Medi-Cal clients, HPSM providers can bill X7942 on a HCFA 1500 form to receive the $9 admin fee. For Healthy Family kids, providers should bill CPT code 90669 on a HCFA 1500 form and the vaccine will be reimbursed at cost.
Simultaneous PCV7 Conjugate & Polysaccharide Vaccine Use: In some circumstances, Prevnar should be given as well as the older polysaccharide vaccine. In children aged 24 - 59 months for whom polysaccharide vaccine would normally be recommended, CDC recommends use of both vaccines with a minimum 2 month interval between the two. These recommendations are based on ACIP and state guidelines (Go to: www.cdc.gov/mmwr/preview/mmwrhtml/rr4909a1. htm).
The AAP recommendations vary slightly and more detail may be obtained at www.aap.org/policy/ re9960.html.
Ongoing Shortage of Tetanus Vaccine As the readers are probably already aware, there is a nation-wide shortage of tetanus vaccine. The Centers for Disease Control and Prevention (CDC) reports that supplies of the tetanus vaccine may not be up to par until next year, following the sudden decision by Wyeth Lederle to stop producing the vaccine, leaving Aventis Pasteur as the only supplier. Supply of Td for patients 7 and older has been in particularly short supply as Aventis has routed much of its production efforts to try and supply sufficient DtaP for younger kids. In the MMWR of May 25, 2001, the CDC recommends restricting the use of Td shots. All routine boosters for children > 7 and adolescents should be deferred until 2002. For the balance of 2001, private and public providers should restrict use of Td to persons in the following categories:
- Persons traveling to countries where diphtheria risk is high
- Persons requiring Td for wound management
- Persons who have received less than 3 doses of any vaccine carrying tetanus and diphtheria toxoids
- Pregnant women who have not received Td within 10 yrs
Chicken Pox Vaccine Requirements: Effective July 1, 2001, chickenpox shots are now required by California state law for admission to (a) kindergarten (or first grade if kindergarten is being skipped), (b) older children < 18 years from out of state or country who enter a higher grade level after July 1, 2001, and (c) children 18 months and older in licensed childcare facilities. Thus, children who attended California kindergarten or higher grades prior to July 1, 2001 are exempt. Also, children can have their physician check off the "had disease" box on their yellow immunization card if clinical history warrants. Blood tests for varicella antibody are NOT recommended as a method of verifying previous exposure or immunization. Also, medical and personal belief exemptions are allowed. Remember: two doses of vaccine are required for children 13 and older.
Hepatitis B and MMR: Remember that state law requires 7 th graders to have started their hepatitis B series and have received their second MMR prior to starting class. Students who haven't completed their series when school starts will be conditionally accepted and must stay on track to finish the series.
Combination Hepatitis A/B Vaccine: GlaxoSmithKline's combination hepatitis A and hepatitis B vaccine, Twinrix, has just received FDA approval. This is the first vaccine to prevent these two diseases in the same product. Clinical trials indicate that 95 percent of patients who received the vaccine--which is given in three doses over six months--were protected from both diseases.
Reminder: A detailed description of childcare and school immunization requirements can be found in both English and Spanish at: www.dhs.ca.gov/ps/dcdc/izgroup/index.htm
Bioterror Preparedness and Planning
Scott Nabity, MPH (Epidemiologist)
In the event of a terrorist act using a biological weapon, the Public Health Division of the Health Services Agency would assume a lead role in the coordination of a medical response. Because acts of terrorism are federal offenses, the FBI will immediately assume jurisdiction for the criminal investigation and the hazardous materials unit of the County Fire Department would direct the containment and decontamination activities at the scene as necessary.
Such roles and other issues are being outlined in a bioterrorism response annex to the Public Health Emergency Preparedness Plan. Because of the diversity of agencies needed for disaster response, San Mateo County has adopted a multi-disciplinary approach to developing a unified plan for response with representatives from local law enforcement, FBI, EMS, public health laboratory, public health nursing, and mental health services. This Bioterrorism Working Group recently conducted tabletop simulations of several biological attacks in an effort to clarify roles and identify weaknesses in the local plan and in our capacity to respond appropriately. These activities are being coordinated by Donald Cheu, MD, Bioterrorism Project Leader for San Mateo County, under a grant provided by the California Department of Health Services. These funds were allocated by the state in response to warnings from international experts about the increasingly realistic threat of bioterrorism in the U.S.
In the coming months the public health team will be working to coordinate response activities with all the hospitals and Emergency Departments in the County. In addition, staff will be providing outreach to providers about surveillance for syndromes suggestive of bioterrorist activities.
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