U.S Novel H1N1 Influenza Meeting to Review the Surveillance System for AI and Pandemic Flu May 7, 2009 Rama Gardens Hotel Bangkok International Emerging Infections Program Thailand MOPH-US CDC Collaboration

Novel H1N1 Influenza The United States Government has declared a public health emergency in the United States in response to this novel H1N1 Influenza. CDC’s response goals are to reduce transmission and illness severity, and provide information to help health care providers, public health officials, and the public address the challenges posed by this emergency.

Novel H1N1 Influenza (continued) In late March and early April 2009, cases of human infection with a novel H1N1 influenza virus were first reported in Southern California and near Guadalupe County, Texas. Other U.S. states have reported cases of swine flu infection in humans and cases have been reported internationally as well.

Novel H1N1 Influenza (continued) Deaths associated with this outbreak of the novel H1N1 influenza have been reported in Mexico and the United States. Hundreds of cases have been reported by other countries. CDC expects the number of cases and deaths to increase.

Pandemic Levels The World Health Organization uses a six-phased approach for easy incorporation of new recommendations and approaches into existing national preparedness and response plans.

What are the symptoms? The symptoms of this novel H1N1 Influenza (formerly referred to as swine flu) in people are similar to the symptoms of regular human flu and include fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting.

How Influenza Viruses Spread Primarily through respiratory droplets – Coughing – Sneezing – Touching respiratory droplets on self, another person, or an object, then touching mucus membranes (e.g., mouth, nose, eyes) without washing hands

Is this a pandemic? During a regular flu season in the United States, we anticipate >200,000 hospitalizations / year 36,000 deaths / year Substantial economic impact ~$37.5 billion in economic costs and pneumonia

Is this a pandemic (continued)? An influenza pandemic is a global outbreak of disease that occurs when: A new influenza A virus appears or “emerges” in the human population, and It causes serious illness in humans, and It spreads easily from person to person worldwide

Global cases as of May 6, 09

Situation reports: USA As of May 6, cases in 41 states (a lot of this due to samples finally getting tested) 845 probable cases in those 42 states. Over 90% turn out to be confirmed so expect case counts to go up a lot. 35 hospitalizations in confirmed cases (4.7% of confirmed and probable) – evolving rapidly Attack rate ~ 22% (seasonal flu 5-20%)

Situation reports: USA 2 deaths. The 2 nd case is the first American to die of this infection All cases: median age 16 yrs (3 months – 81 years). 62% under 18 1/3 of confirmed cases have some link to Mexico but most do not

Situation reports: USA Still detecting a fair amount of seasonal flu, mostly H3N2  May be due to heightened surveillance  ILI visits above threshold that normally designates an influenza system Mortality data has also increased slightly

Situation reports: USA Lab looking at cross protective antibodies Older adults may have antibodies with some cross protection This is just in vitro data so far Children have little in the way of antibodies that might be cross protective Prevalence of potentially cross protective antibodies increases with age

Situation reports: USA To date, all tested viruses were resistant to Amantadine and Rimantadine, but susceptible to Oseltamivir and Zanamivir

Use of Rapid Influenza Diagnostic Tests for Patients with ILI during Novel H1N1 outbreak Data are not yet available to inform recommendations on the use It is reasonable to assume that rapid tests that detect Flu A viral nuceoprotein antigen can detect novel H1N1 in respiratory specimens Sensitivity & specificity on H1N1 is not yet known Data subsequently shown here are anecdotal Clinicians may consider using rapid tests as part of their clinical evaluation of patients, but results should be interpreted with caution. Positive from rapid tests must be confirmed by RT-PCR or viral culture

Use of Rapid Influenza Diagnostic Tests for Patients with ILI during Novel H1N1 outbreak Reliability of rapid tests depends largely on the conditions under which they are used, and are entirely based on experiences with seasonal flu For seasonal flu, sensitivity ~ 50-70% when compared to RT- PCR or viral culture, but specificity ~ 90-95% False-positive and true-negative results are more likely to occur when flu is uncommon in the community, typically at the beginning or the end of an outbreak False-negative and true-positive results are more likely to occur when flu is common in the community, typically at the height of an outbreak Sensitivity varies depending on when in the course of illness the specimen is collected. Specimens collected during the first 4-5 days of illness is greatest.

Use of Rapid Influenza Diagnostic Tests for Patients with ILI during Novel H1N1 outbreak How to interpret a positive test A patient with a positive test for flu B likely infected with seasonal flu B or is a false positive result. Such patient is unlikely to have infection with novel H1N1. Several possibilities when a patient tests +ve for flu A – Might have novel H1N1 – Might have seasonal flu A or – Might have a false positive result

Use of Rapid Influenza Diagnostic Tests for Patients with ILI during Novel H1N1 outbreak How to interpret a negative test H1N1 flu infection cannot be excluded when a patient tests negative for flu A by rapid test. If a patient has an epidemiologic link to a confirmed case, or has either traveled to or resides in an area where there are one or more confirmed H1N1 cases, further testing and treatment should be based upon clinical suspicion, severity of illness, and risk for complications. If a patient has mild illness and no epidemiologic link, further testing and treatment are not recommended

Investigations of H1N1 infections in a school – NYC On Apr 24, 09, CDC reported 8 confirmed cases of novel H1N1 virus infection in Texas & California The strain identified in U.S. patients was confirmed as genetically similar to viruses subsequently isolated from patients in Mexico To date, confirmed cases among students and staff member of a New York City (NYC) school remain a large proportion of confirmed patients in the U.S. Source: MMWR April 30, 2009 / Vol. 58 / Dispatch - Swine-Origin Influenza A (H1N1) Virus Infections in a School — New York City, April 2009 (

Investigation of H1N1 infections in a school – NYC Apr 23, 09 – NYC health department was notified of ~ 100 cases of mild (uncomplicated) respiratory illness among students at a high school in NYC with 2,686 students and 228 staff members During Apr 23-24, a total of 222 students visited the school nursing office and left school NYC health department mobilized officers to go and collect nasopharyngeal swab from symptomatic students at the school and from students absent due to illness

Investigation of H1N1 infections in a school – NYC Decision was made not to open the school the following week Contact and suspected cases in neighborhood also had NP swab collected 44 cases out of 53 tested positive for novel H1N1 Telephone interview with 44 confirmed cases was conducted

Investigation of H1N1 infections in a school – NYC CharacteristicN = 44 Median age15 (range: 14-21) StudentsAll but one student teacher Sex31 (70%) were female Race - Non-Hispanic white - Hispanic - non-Hispanic black - others 30 (68%) 7 (16%) 2 (5%) 5 (11%) Travel None reported recent travel to CA, TX, or Mexico (Several students participating in the separate on-line survey reported travel to Mexico. None had confirmed H1N1 by PCR.)

Investigation of H1N1 infections in a school – NYC CharacteristicN = 44 Illness onsetApr 20 – 24 (see Epi curve) Symptoms - Cough - Fever - Fatigue - Headache - Sore throat - Runny nose - Chill - Muscle ache - Nausea - Stomach ache - Diarrhea - Shortness of breath - Joint pain 43 (98%) 42 (96%) 39 (89%) 36 (82%) 35 (80%) 24 (55%) 22 (50%) 21 (48%) 20 (46%)

Epidemic curve: Outbreak in NYC school Number of confirmed cases (N=45) of novel Flu A (H1N1) virus infection in a school, by date of illness onset, April 2009

Investigation reports: International Reports from Mexico suggest that epidemic curve might be flattening there Studies – spectrum of illness, community transmission, clear clinical description Spectrum of disease: Trying to do community survey in a place where denominator can be defined – serosurvey

Surveillance transition in US –State reporting From line list to aggregate report: total cases, deaths, hospitalizations Move toward population-based surveillance: existing surveillance systems, random sample surveys –Laboratory Moving to being done at state labs confirmation testing of 2009-H1N1 –Assessing cases in specific population cases: pediatric, maternal and infant, and health care workers (important for severity & future vaccine considerations)

Summary Human infections with a novel Influenza A (H1N1) virus have been documented in multiple countries around the globe Virus was first identified in North America; currently few confirmed cases to in East Asia High proportion of cases in young adults and children Clinical spectrum still not well-defined but early cases suggest clinical course similar to seasonal influenza

Final notes Because this is a new virus, most people will not have immunity and illness may be more widespread Therefore, it is important to prepare for the potential of a large number of persons becoming ill and the impact on Workforce, including health care workers Health care services (e.g., hospital beds, ventilators) Public works (e.g., water, sewer, transportation) Socio-economic issues Thailand and other countries in this region are fortunate that the outbreak started in North America and we have a short window of time to prepare

Resources For the most current information on the H1N1 influenza outbreak, visit Some useful guidance can be retrieved at includes clinician guidance for patients, treatment, screening & specimen collection, laboratories, guidance for schools and university, guidance for pregnant and breastfeeding women, and travel guidance