| Epidemiological Bulletin: Spring 2001
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Recent Measles Cases in San Mateo County
Beth Schulz, PHN, MPH (CD Control Officer) & Francis Wiser, MSPH (Epidemiologist)
Recent incidents involving imported cases of measles are pointing out issues with vaccine coverage and the potential for measles reintroduction. In the largest recent incident, the Seattle area has seen at least 11 diagnosed cases of measles in January and early February of 2001, with further spread possible from infectious individuals attending large sporting events and similar events. Additionally, in mid-February, 4 cases of measles were diagnosed in a very large group of foreign high school students on a tour of theme parks in Southern California. These situations have somewhat overshadowed our own local measles incidence with 4 cases in 3 months.
The first local case was a 39-year old US-born male who traveled to the Philippines from 11/5-21. Fever and cough developed a week after he returned, with rash onset on 12/2. He went to a local hospital 4 times while infectious, including a visit to the ER for rehydration. Measles was never suspected. The second case, his 1 year-old daughter, developed a 105¡ F fever and sore throat on 12/8. She visited a clinic on 12/11, but did not develop a rash until 12/12, when her pediatrician diagnosed and then serologically confirmed measles in both father and daughter. A further related measles case occurred in an 8 month-old infant who attended the same day care as the second case. This infant attended a holiday gathering in San Francisco while infectious, exposing several children under 1 years of age, along with a pregnant woman. To complicate matters, two other susceptible day care contacts exposed to the younger case developed afebrile rash illnesses during this time frame.
Of these latter two, one was diagnosed not with measles but with human herpes virus 6 (roseola); the other child was not serologically tested due to previous receipt of immune globulin. Although they had clinical signs inconsistent with measles, these two were managed as potential cases because they were susceptible contacts to a confirmed case. In addition, over 200 other contacts to the confirmed cases were later identified and monitored for 18 days post-exposure. Many susceptible contacts were greatly inconvenienced during the holidays and had to cancel travel and other holiday plans.
Just as the response to these 3 cases was winding down, another infectious case, this one in a 30 year-old woman, was seen on 3/1 at another area ER. This person had just flown in from Australia, where she'd been exposed to a confirmed case. Tracking, monitoring and prophylaxis of her contacts in the ER and elsewhere is ongoing.
All of these follow-up measures would have been unnecessary if the index cases had been properly immunized against measles prior to their trips. The adult male case, born in 1960, thought he had immunity to measles and rubella, but in fact, had neither. The risk of exposure to measles outside the US remains high, as measles remains common in many countries, including some developed nations in Europe and Asia. Measles is extremely communicable, with a >90% secondary attack rate among exposed susceptibles. Airborne transmission has been documented in closed areas up to 3 hours after an infected person departs from the room. Persons born before 1957 are likely to have had measles disease and generally are considered immune. However, persons born from 1957-1968, even if vaccinated during that period, may not have current measles immunity. In particular, from 1963- 1967 an inactivated "killed" measles vaccine was licensed for use in the U.S. which did NOT adequately protect against measles. In 1967, this vaccine was withdrawn and subsequently more effective live attenuated measles vaccines were used. Although vaccination against measles, mumps and rubella is not required for international travel, persons planning such travel should ensure that they are immune to these diseases. Persons born after 1957 can be considered immune to measles if they have documentation of physician-diagnosed measles, lab evidence of immunity or proof of 2 doses of live measles vaccine on/after their 1st birthday.
These regional clusters of measles come at a time when global health planners are exploring the feasibility of eliminating measles altogether. Despite this, foreign immunization policies, increased travel and possibly some American parental reluctance to immunize children due to perceived risks of the MMR vaccine are combining to create a situation where sporadic introductions of the disease may affect unexpectedly susceptible populations in the US. In this context, the DCPU would like to remind providers to consider measles when evaluating febrile or rash illnesses, and to pursue immunization or travel histories when appropriate.
For more information regarding measles control and foreign immunization policies, please contact the DCPU at (650) 573-2346 or visit the CDC Traveler's Health Website at: www.cdc.gov/travel/diseases/measles.htm. Providers may especially wish to review the indications and dosage for the use of immune-globulin for contacts at high risk of complications or those for whom vaccine is contraindicated. group A strep.
Review of 3 Fatal Cases of Streptococcal Meningitis
Gloria Tzuang, MPH (Epidemiologist) & Beth Schulz, PHN, MPH (CD Control Officer)
In the past 6 months, the DCPU received 3 reports of fatal ¥ -hemolytic strep infections. The first was a male in his early 30s who presented to an ER with delirium and severe exudative pharyngitis. He was hospitalized following an episode of respiratory arrest in the ER and in the subsequent 6 weeks developed renal failure, duodenal ulcer, ARDS and necrosis of large areas of skin on the lower extremities, before finally dying of cardiac arrest. Group A strep was isolated from blood, throat and sputum cultures. In addition, group B strep ( Streptococcus agalactiae) was isolated from the blood.
The second case was a previously healthy female in her early 50s, with no recent history of pharyngitis, surgical procedures, wound or blunt trauma. She presented at an ER with a 48 hr history of flu-like malaise, rash, and extreme, escalating thoracic and abdominal area pain. The patient was experiencing hypotensive shock (BP 86/59, tachycardia, elevated liver function tests, confusion) and renal impairment (creatinine 9.4 mg/dL, protein in urine 5.7). The patient succumbed to cardiac arrest shortly after emergency surgical debridement of necrotic tissues. Blood and debrided tissue cultures were both positive for group A strep.
The third patient was a female in her late 50s with no underlying diseases who presented with meningitis and grand mal seizures. She also experienced renal impairment and ARDS, progressing to shock and cardiac arrest, but no soft tissue involvement. CSF cultures were positive for Invasive infections of ¥ -hemolytic streptococci, most commonly group A strep (GAS), can cause a range of symptoms: from mild, noninvasive illness such as pharyngitis or impetigo to severe illness such as pneumonia, bacteremia, necrotizing fasciitis (NF) and streptococcal toxic shock syndrome (STSS.) Death occurs in 10-13% of l invasive cases, 25% of NF cases, and 45% of STSS cases.1 Although invasive infections resulting from pharyngitis are rare, some strains of GAS can cross membrane barriers to enter the blood or CSF.2 Necrotizing fasciitis can result from a variety of events: blunt trauma; hematoma; muscle strain; viral infections, such as varicella or influenza; surgical procedures; or injection drug use.2,3 Roughly half of NF cases have no apparent portal of entry and remains a rare but disturbing presentation of streptococcal infection. In most cases of invasive GAS infection, prophylaxis of casual contacts is not recommended. The decision to prophylax household contacts should be based on the severity of the disease. At the very least, susceptible contacts should be tested and treated based on positive culture results.
For more information and statistics, refer to: 1. www.cdc.gov/ncidod/dbmd/diseaseinfo/ groupastreptococcal_t.htm
2. Bisno AL and Stevens DL. Streptococcus pyogenes (Including Streptococcal Toxic Shock Syndrome and Necrotizing Fasciitis). In: Mandell GL, Bennett JE, and Dolin R, eds. Principles and Practice of Infectious Diseases, 5 th ed. Philadelphia: Churchill Livingstone; 2000: 2101-2116, 2156-2166.
3. www.cdc.gov/ncidod/EID/vol1no3/stevens.htm
Update on Influenza and RSV Season
Sam Stebbins, MD, MPH (Deputy Health Officer)
Influenza A and B In general, it has been a relatively mild influenza season, with a low peak of activity occurring in the second week of 2001. This contrasts with last year, which had a high, sharp spike in Northern California during the last week of 1999 and first week of 2000. The predominant strains of influenza A and B have closely matched the ingredients of the vaccine, although we are seeing some drift in influenza B, which may lead to a change in the vaccine formulation for next year. There also appears to be more B this year than last, but this may be a statistical anomaly: H1N1 remains the predominant strain of A, and since this variant has been around for a long time, many people have antigenic memory to it, don't get as sick, and thus don't visit their doctor or have a test for influenza.
The national trend has been reasonably similar to California's, although certain regions have had much more flu activity. Influenza is currently considered "widespread" in Washington, Utah, Colorado, Oklahoma, Minnesota, Mississippi, Tennessee, North Carolina, Virginia and Connecticut.
For more information, please see the CDC website at: www.cdc.gov/ncidod/diseases/flu/weekly.html. Local influenza activity is monitored and reported by the state DHS Communicable Disease Division. The state gathers the following data on a weekly basis: Confirmed influenza cultures with subtyping; admissions for "influenza" at Northern and Southern California Kaiser sites; prescriptions written for influenza medication at Northern and Southern California Kaiser sites; and outpatient visits for "influenza-like illness" at both CDC and state sentinel sites. Since culture-confirmation of influenza cases is proportionally small and can lag behind actual influenza activity, the sentinel sites and prescription information provide a more "real-time" snapshot of influenza activity.
Respiratory Syncytial Virus (RSV) RSV has had an active year so far, with many more lab-confirmed cases than influenza and a sharp spike, which has just peaked. Historically, the peak of RSV season occurs 6-8 weeks after the peak of influenza season, so there are a lot of cases of RSV currently going around. RSV is most notable for causing lower-respiratory illness in children under 2 years of age. RSV can also cause repeat infections throughout life, usually associated with moderate-to-severe cold-like symptoms; however, severe lower respiratory tract disease may occur at any age, especially among the elderly or among those with compromised cardiac, pulmonary, or immune systems. For more information, go to: www.cdc.gov/ncidod/dvrd/nrevss/rsvfeat.htm.
New Physician Training Materials from AMA
Staff (Disease Control and Prevention Unit)
After a more than yearlong lull in food-borne outbreak reports, the DCPU had to follow up on 6 outbreaks of various sizes between Oct-Dec 2000, including the exceptionally large Viva Mexico outbreak. In addition, the profile of food-borne illnesses seems to be rising in the media over the past year or two Ð with articles appearing on food-related diseases and increasing public concern over whether or not transmissible spongiform encephalopathies (e.g. mad cow disease) pose a threat to the public. In San Mateo County, more so than in many parts of the US, the population has high rates of eating out, exposure to many imported foodstuffs and a preference for raw and "naturally prepared" foods.
In this context, providers may find extra knowledge of food-borne illnesses and outbreak response useful. With this in mind, the AMA has just released a large packet of instructional materials on food-borne illnesses for physicians. This material, collected under the title Diagnosis and Management of Food-borne Illnesses: A Primer for Physicians is available for free on the Web at www.ama-assn.org/ama/pub/category/3629.html.
We highly recommend that physicians and other providers obtain and review this material. In addition, others who want information on these topics can find it from several on-line sources. The CDC has a FAQ on food-borne illness at www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinf ections_g.htm, while the FDA has a variety of food safety links under the page for the Center for Food Safety and Applied Nutrition at vm.cfsan.fda.gov/list.html. Finally, for those interested in the mechanics of outbreak control and investigation, the CDC's Division of Bacterial and Mycotic Diseases has a great deal of information, including statistics and investigatory forms (look at the left hand column), on the page for the Foodborne Outbreak Response and Surveillance Unit at www.cdc.gov/ncidod/dbmd/outbreak/.
Large Outbreak of Shigella sonnei
Francis Wiser, MSPH (Epidemiologist)
A party of 11 persons attended a luncheon at Viva Mexico Restaurant (VM) on 10/20. At least 6 of those persons then called in sick on 10/23. Office staff noted the clustering of illness in lunch attendees, and became concerned on 10/24 when they learned that one of the 11 - a resident of Santa Clara county - had died at home late on 10/23. That prompted a complaint on 10/24 to San Mateo County Environmental Health Services (EHS), who immediately informed the Disease Control and Prevention Unit (DCPU) of a probable food-borne outbreak.
On 10/24, VM was inspected by EHS and the inspectors observed a wide array of poor food handling practices, including inadequate staff hand washing, problems with cross contamination of surfaces, as well as improper cold storage of large containers of warm food. VM was ordered closed mid-day on Tues, 10/24 and was only allowed to reopen on 11/29, after extensive cleaning and detailed sanitary retraining of the restaurant's staff.
Methods and Results: The DCPU initiated immediate epidemiologic follow-up on 10/24. Early follow-up calls to persons in the initial dining party soon elicited other leads to diners, even as positive Shigella sonnei culture reports began to arrive from laboratories on 10/25. In an outbreak follow-up effort of unusually large scale at the county level, San Mateo County DCPU personnel eventually identified over 460 potentially affected persons and interviewed 398 of those for information on illness and food history. A case-control comparison of ill vs. well diners was also performed on the food history data.
Figure 1. Illness Distribution Viva Mexico Outbreak, Redwood City, CA, 10/00)
Of 398 responders, 222 (58.1%) reported illness, while an additional 16 were excluded from the analysis due to non-specificity of symptoms. Of the 222 ill, the most common symptoms aside from diarrhea (100.0%) were abdominal cramps (91.1%), fatigue (88.6%), chills (84.4%), fever (82.0%) and nausea (77.4%). The high proportion with fever and chills are particularly indicative of shigellosis. Incubation periods in the ill persons varied from 7 to 97 hours, with a median incubation of 44 hours, roughly paralleling the incubation period range and median outlined in medical references for S. sonnei. Eight of the 222 had incubation periods longer than 100 hours and were both classified as likely secondary cases and excluded from the case-control analysis. These eight are a low estimate of the number of secondary cases, as some individuals with shorter incubations may have also been secondary and not primary transmission.
Among the 222 reported cases, 71 (32.0%) were eventually confirmed by culture as S. sonnei . The one deceased person in the sample was also classified as a culture-confirmed case on the basis of a positive culture of gastric contents. In fact, in mid-November, the Santa Clara Medical Examiner assigned the final cause of death as "complications of Shigella enteropathy," with "hypertensive cardiovascular disease" listed as a contributing cause of death. All isolates from this outbreak that have had anti-microbial sensitivities done were resistant to Septra- (TMP-SMX) and ampicillin, but susceptible to quinolones, cefixime and cefotaxime.
Cases with culture confirmation initially experienced exposure starting on 10/19, and continued in lesser numbers until 10/22, two days prior VM's shut-down. Report-only cases also tapered off significantly by 10/23-23, indicating that Shigella infection peaked 10/20 and was lessening before being terminated by the restaurant's closure.
As for specific foods consumed, the case-control study generated results that most consistently implicate the salsa as the primary vehicle of transmission (O.R.=3.99, p=0.0029.) While other food items show some sporadic association in portions of the analysis, the table salsa is the only food item that appears to be significantly associated with illness across all analyses. The table salsa also had the most elevated odds ratio in all analyses. Discussion: That S. sonnei was the causative pathogen became apparent early in this investigation. That fact, along with the outbreak's sheer size, makes this incident unusual. With 222 reported cases of illness and 1 fatality, this stands as the most serious food-borne disease outbreak in San Mateo County in many years.
All VM staff tested negative for S. sonnei, although some of the tests were not obtained in a timely manner. In addition, no pathogens have been isolated from food samples from VM. In addition, the State Food and Drug Branch (FDB) is conducting a 'trace back' of the implicated salsa ingredients, notably cilantro and green onions, both which have been implicated in previous Shigella outbreaks involving salsa at Mexican restaurants.
The resistance pattern of the Shigella in this outbreak is consistent with many reported on the West Coast since the early 1990's. This outbreak should remind local providers that ampicillin and TMP-SMX are no longer appropriate treatments for S. sonnei infection.
Conclusions: Given the broad spectrum of poor sanitary practices observed by the EHS inspectors at VM, transmission of Shigella in this situation was most likely due to transmission from ingredient contamination or from infected food handling staff, with possible further spread via unsanitary food handling procedures. The vehicle of transmission appears to have been the table salsa, although concurrent contamination of other food items may well have been present. There is also a possibility that an infected diner introduced the pathogen into VM on or about 10/18-19. Even in this unlikely event, such extensive spread of the Shigella would only have been made possible by the above-mentioned poor food-handling practices.
Update on Asthma Surveillance Acticities
Gloria Tzuang, MPH (Epidemiologist)
Although nationally asthma is the most common chronic disease in children, there is very little data to back up this assertion in San Mateo County. Asthma prevalence in the County is unknown for all age groups. Hospitalization data only provide a glimpse of the tip of the iceberg - the most severe cases. In addition, there is no information on what proportion of patients are treated according to NHLBI protocol, medication compliance rates, or what factors affect compliance. The current public health model of asthma prevention utilizes the community-based coalition approach. This model encourages persons with asthma, their families, health care providers, and community members to join together to control the disease. The County Health Services Agency will be working with various healthcare and community groups to develop such a coalition. The Public Health Division also recently received a small planning grant from the Children and Families First Commission to organize a countywide task force to focus on asthma in early childhood. As part of the broader coalition, this task force will develop a specific plan to gather data, raise awareness, and work with the community on asthma in children 0 to 5 years of age.
A Note on HIV Reporting
Francis Wiser, MSPH (Epidemiologist)
The DCPU would like to remind medical providers of some changes in local AIDS/HIV surveillance procedures. Firstly, since July 2000, our Communicable Disease investigators (CDIs) have been available to perform Partner Counseling and Referral Services (PCRS) - that is, to notify and counsel partners/contacts of any patients who are HIV-positive or AIDS diagnosed. Providers are advised that if they have HIV or AIDS patients who are not comfortable notifying their sexual or other contacts of their risk, but who do wish such notification to occur, our three CDI staff (with over 72 years of STD/ HIV notification and counseling experience between them) can do it for them in a completely confidential and professional manner. In another area of surveillance, legally required reporting of HIV infection, enacted in 2000 and using unique identifier codes instead of names, is now tentatively scheduled to begin late in 2001. The California Department of Health Services is working to finalize reporting procedures. We expect that state guidelines will require reporting providers to assign the unique identifier code to each patient reported.
Further information will be made available in forthcoming issues of this Epidemiology Bulletin. Providers who have reported substantial numbers of AIDS cases in the past will be notified of procedures and resources by mail and visits from DCPU staff. Inquiries about PCRS services can be directed to Senior CDI Jim Olson at (650) 573-2346, while questions about developments in HIV reporting and AIDS surveillance procedures can be addressed to Epidemiologist Sarah Cottrell at the same number.
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