Print this article | Email this article

Santa Clara County Influenza Surveillance - February 03, 2010

The summary countywide data will continue to be updated. All data are considered provisional and are subject to change.

Highlights

• During week 4 (January 24-30, 2010), influenza activity decreased slightly in our county. There were 6 hospitalizations associated with influenza, and no influenza- related deaths have been reported in the past 4 weeks.
• The Santa Clara County Public Health Laboratory now has the ability to subtype for H1N1 influenza. Previously, positive influenza specimens were sent to the California for confirmatory testing of the influenza A (H1N1) subtype. Last week, one specimen tested positive for influenza A (Unable to Subtype/Probable H1N1).
• Overall influenza activity in California has been downgraded to “sporadic” (defined by the CDC as “small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI”).

INFLUENZA CASE REPORTING

Novel H1N1 influenza A, now known as 2009 Pandemic H1N1 influenza, was initially made reportable in April 2009. From April to July 2009, all H1N1 confirmed and probable cases – both outpatient and hospitalized – were reported to the local health department. Beginning in July, only hospitalized cases were reportable and counted, and effective mid-August, the California Department of Public Health (CDPH) initiated weekly aggregate reporting for all hospitalized cases of influenza. Since aggregate reporting began, the date of symptom onset is not collected on hospitalized cases. Now, only ICU and fatal cases are reported individually. Both aggregate weekly hospital reports and individual case reports are submitted to the California Department of Public Health (CDPH).

The number of influenza cases reported below captures severe cases that have resulted in hospitalization and reflects only a portion of the actual number of influenza cases in Santa Clara County. Laboratory testing is limited to individuals with serious influenza-like illness, including hospitalized patients, and those at high risk for complications.

Table 1: Cumulative number of influenza cases by hospitalization (H1N1 and other influenza), ICU (H1N1), and deaths (H1N1 and other influenza), reported in Santa Clara County and California - (April 2009 to January 30, 2010)

Table 2: Cumulative number of hospitalized influenza (H1N1 and other influenza) cases reported in Santa Clara County, by age group – (April 2009 to January 30, 2010)

Age Group	Number of Cases	Percent
<1	83	8%
1 - 4	123	12%
5 - 18	225	22%
19 - 24	44	5%
25 - 35	104	10%
36 - 49	106	10%
50 - 64	167	16%
65+	177	17%
TOTAL	1,029

Figure 1: Hospitalized and ICU influenza (H1N1 and other influenza) cases reported to Santa Clara County Public Health Department by week of report - (April 2009 to January 30, 2010).

(click to enlarge)

Figure 2: Cumulative number of hospitalized and ICU influenza (H1N1 and other influenza) cases reported to Santa Clara County Public Health Department - (April 2009 to January 30, 2010).

(click to enlarge)

Figure 3: Deaths associated with pandemic H1N1 influenza reported to Santa Clara County Public Health Department, by week of death - (April 2009 to January 30, 2010).

(click to enlarge)

SYNDROMIC SURVEILLANCE

ESSENCE (Electronic Surveillance System for the Early Notification of Community-Based Epidemics), is a real time, automated syndromic surveillance system that collects chief complaint data from Emergency Department visits at five Santa Clara County hospitals. The hospitals represented by this system include Columbia Good Samaritan, O’Connor Hospital, Regional Medical Center, St. Louise Regional Hospital, and Valley Medical Center.

Figure 4: Number of visits to Santa Clara County hospital emergency departments for a respiratory syndrome*, in patients age <18 years, by date of visit. Reporting period: past 90 days from February 3, 2010.

(click to enlarge)

Figure 5: Number of visits to Santa Clara County hospital emergency departments for a respiratory syndrome* in patients age >=18, by date of visit. Reporting period: past 90 days from February 3, 2010.

(click to enlarge)

* Respiratory syndrome includes: Acute Bronchitis, Lower Respiratory Infection Bronchitis, Otitis Media, Chest Congestion, Pneumonia, Nasal Congestion, Shortness Of Breath, Cough, SoreThroat, Difficulty Breathing, Upper Respiratory Infection, Hemoptysis, Wheezing, Laryngitis.

LABORATORY SURVEILLANCE

Table 4: Virologic Surveillance Data, Santa Clara County Public Health Laboratory. Reporting period: April 27, 2009 to January 30, 2010.

Figure 6:  Influenza testing results, by subtype and week of specimen submission to the Santa Clara County Public Health Laboratory. Reporting period: April 2009 to January 30, 2010.

(click to enlarge)

SENTINEL PROVIDER INFLUENZA SURVEILLANCE

The California Sentinel Provider Influenza Surveillance Program is a partnership between clinicians, local health departments (LHDs), the California Department of Health Services (CDPH), and the federal Centers for Disease Control and Prevention (CDC) to conduct surveillance for influenza-like illness (ILI). Providers of any specialty in any type of practice are eligible to be sentinel providers. The information provided by the sentinel providers show the impact of influenza-like Illness in the outpatient population.

Figure 7: Number of patients seen by reporting Santa Clara County sentinel providers and the percentage of patients with Influenza-Like Illnesses (ILI). Reporting period: September 2008 – January 2010.

(click to enlarge)

Figure 8: Total Number of Patients Presenting with Influenza-Like Illnesses (ILI), by Age Group. Reporting period: January 2009 to January 30, 2010.

(click to enlarge)

SCHOOL SURVEILLANCE

At the beginning of the school year, 18 schools agreed to participate in school absentee surveillance. Currently, 21 schools are participating. Schools report the number of students absent due to illness. This information is only a sample of schools in Santa Clara County and provides a limited picture of the illness trends in schools.

Figure 9. Percent of elementary school students absent due to illness. Reporting period August 19, 2009 to January 30, 2010.

(click to enlarge)

Figure 10. Percent of high school students absent due to illness. Reporting period August 19, 2009 to January 30, 2010.

(click to enlarge)

---

Back to Top | Print this article | Email this article