Pandemic (H1N1) 2009 Surveillance in New York City | CDC EID

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Volume 16, Number 8–August 2010
Research
Pandemic (H1N1) 2009 Surveillance for Severe Illness and Response, New York, New York, USA, April–July 2009
Sharon Balter, Leena S. Gupta, Sungwoo Lim, Jie Fu, and Sharon E. Perlman , for the New York City 2009 H1N1 Flu Investigation Team
New York City Department of Health and Mental Hygiene, New York, New York, USA

Suggested citation for this article

Abstract
On April 23, 2009, the New York City Department of Health and Mental Hygiene (DOHMH) was notified of a school outbreak of respiratory illness; 2 days later the infection was identified as pandemic (H1N1) 2009. This was the first major outbreak of the illness in the United States. To guide decisions on the public health response, the DOHMH used active hospital-based surveillance and then enhanced passive reporting to collect data on demographics, risk conditions, and clinical severity. This surveillance identified 996 hospitalized patients with confirmed or probable pandemic (H1N1) 2009 virus infection from April 24 to July 7; fifty percent lived in high-poverty neighborhoods. Nearly half were <18 years of age. Surveillance data were critical in guiding the DOHMH response. The DOHMH experience during this outbreak illustrates the need for the capacity to rapidly expand and modify surveillance to adapt to changing conditions.
On April 23, 2009, a nurse from a high school in New York City (NYC) called the Department of Health and Mental Hygiene (DOHMH) to report an outbreak of respiratory illness (1). The cause of the outbreak was rapidly confirmed to be influenza A pandemic (H1N1) 2009 virus. This outbreak was detected just a few days after initial reports of mild disease caused by pandemic (H1N1) 2009 virus in California and Texas (2,3) and at the same time as an outbreak of severe respiratory disease associated with pandemic (H1N1) 2009 virus in Mexico (4). Information about the clinical severity and transmission characteristics of this new influenza virus was limited. Given preliminary media reports about the Mexican outbreak and concern that NYC might also experience widespread severe disease, DOHMH launched a large-scale public health response.

Before the spring of 2009, DOHMH routine surveillance systems for influenza included 1) syndromic surveillance for medication sales, school absenteeism, and emergency department visits for influenza-like illness (ILI) (5,6); 2) electronic laboratory reporting of confirmed cases from commercial and hospital laboratories; 3) active surveillance of all NYC virology laboratories to determine the weekly number of specimens submitted for influenza testing and the percentage of those positive; 4) typing samples of influenza isolates obtained from patients in NYC hospitals at the DOHMH Public Health Laboratory (PHL); 5) enhanced passive surveillance for pediatric influenza deaths; 6) monitoring trends in influenza and pneumonia-related mortality through the DOHMH Vital Registry; and 7) monitoring outpatient ILI through the Centers for Disease Control and Prevention (CDC; Atlanta, GA, USA) Influenza-like Illness Surveillance Network (7), a sentinel network through which providers reported weekly on the proportion of ILI in their practices during influenza season. The DOHMH had also created a plan for local response to a potential influenza pandemic, including enhanced surveillance to guide public health officials in determining how to prioritize use of antiviral agents and vaccines (8). Surveillance data could also inform community control measures, such as school closures. Proposed surveillance strategies in this plan focused on mechanisms for monitoring trends in hospitalizations and deaths, but not necessarily for trying to count every severe case. Methods were also proposed for obtaining more detailed clinical and epidemiologic data for a sample of cases.

The DOHMH also has an incident command system (ICS), an agency-wide structure for addressing and responding to emergencies that is different from the usual DOHMH structure. Divided into 10 sections, the ICS is led by an incident commander who reports directly to the Commissioner of Health (9). All DOHMH employees are assigned to a section within the ICS and can be called on to assist their section upon activation of the system. In a public health emergency, the Surveillance and Epidemiology Section establishes and conducts surveillance to assess the illness and deaths associated with the event and conducts any needed epidemiologic studies to guide the public health response. ICS activation provides surge capacity by increasing the workforce available to conduct surveillance or epidemiologic activities beyond the staff members who are normally responsible for the specific disease or public health issues involved in the emergency.

We describe some of the surveillance methods used in the investigation of pandemic (H1N1) 2009 in NYC from April to July 2009. DOHMH investigated the high school outbreak (1,10), and set up an enhanced citywide surveillance system to track the scope and severity of infections. The agency also prioritized identification and diagnostic testing of patients with severe or fatal cases of ILI in hospitals or clusters of those with ILI in schools and other congregate settings; this surveillance was essential because evidence of severe pandemic (H1N1) 2009 would have prompted more aggressive public health control measures. In addition, because surveillance of cases in hospitalized patients, and particularly of fatal cases, was an important part of this investigation, we provide an overview of epidemiologic findings among hospitalized patients.

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Pandemic (H1N1) 2009 Surveillance in New York City | CDC EID

Suggested Citation for this Article
Balter S, Gupta LS, Lim S, Fu J, Perlman SE; New York City 2009 H1N1 Flu Investigation Team. Pandemic (H1N1) 2009 surveillance for severe illness and response, New York, New York, USA, April–July 2009. Emerg Infect Dis [serial on the Internet]. 2010 Aug [date cited]. Available from
http://www.cdc.gov/EID/content/16/8/1259.htm

DOI: 10.3201/eid1608.091847