CID Study: Airborne Norovirus In Healthcare Facilities

 

# 10,033

As the CDC graphic above illustrates, when it comes to infectivity, Norovirus is hard to beat.   The `accepted’ mode of transmission has long been the fecal-oral route, but over the past few years we’ve seen evidence supporting an `airborne’ or aerosolized transmission.

 

Last week, a new study was published in Clinical Infectious Diseases that looked for, and found, norovirus in ambient air samples taken at from 8 hospitals, both  inside and outside of an infected patient’s room.

 

First a link to the study, and some excerpts from the abstract and press release, after which I’ll return with more:

 

Detection and quantification of airborne norovirus during outbreaks in healthcare facilities

Laetitia Bonifait1,  Rémi Charlebois1, Allison Vimont2, Nathalie Turgeon1, Marc Veillette1, Yves Longtin3, Julie Jean2,4, and Caroline Duchaine1,5

ABSTRACT

Methods. A total of 48 air samples were collected during norovirus outbreaks in 8 healthcare facilities. Samples were taken 1 m away from each patient, in front of the patient's room and at the nurses' station. The resistance to aerosolization stress of murine norovirus MNV-1 bioaerosols was also tested in vitro using an aerosol chamber.

Results. Norovirus genomes were detected in 6/8 healthcare centers. The concentrations ranged from 1.35x10¹ to 2.35x10³ genomes per m³ in 47% of air samples. Norovirus MNV-1 preserved its infectivity and integrity during in vitro aerosol studies.

Conclusion. Norovirus genomes are frequently detected in the air of healthcare facilities during outbreaks, even outside patients' rooms. In addition, in vitro models suggest this virus may withstand aerosolization.

 

An accompanying press release to the CID study states:

According to Professor Duchaine, this previously unknown mode of norovirus propagation could explain why gastroenteritis outbreaks are so hard to contain: "The measures applied in hospital settings are only designed to limit direct contact with infected patients. In light of our results, these rules need to be reviewed to take into account the possibility of airborne transmission of noroviruses. Use of mobile air filtration units or the wearing of respiratory protection around patients with gastroenteritis are measures worth testing."

 
Currently, the recommendations from the CDC on the Healthcare Worker’s use of PPEs (Personal Protective Equipment) when dealing with Norovirus reads:

 

Personal Protective Equipment

1. If norovirus infection is suspected, adherence to PPE use according to Contact and Standard Precautions is recommended for individuals entering the patient care area (i.e., gowns and gloves upon entry) to reduce the likelihood of exposure to infectious vomitus or fecal material.    (Category IB)(Key Question 1.C.4) 
2. Use a surgical or procedure mask and eye protection or a full face shield if there is an anticipated risk of splashes to the face during the care of patients, particularly among those who are vomiting. (Category IB)(Key Question 3.C.2.a)
3. More research is needed to evaluate the utility of implementing Universal Gloving (e.g., routine use of gloves for all patient care) during norovirus outbreaks. (No recommendation/unresolved issue)

 

Most of the CDC’s guidance documents for HCWs dealing with Norovirus cases stress patient cohorting and hand hygiene.  Respiratory protection isn’t mentioned in any of the following documents.

• Overview: A Norovirus Outbreak Control Resource Toolkit for Healthcare Settings  [PDF - 306 KB]
• Poster: What healthcare providers should know  [PDF - 185 KB]
• Fact Sheet: Norovirus in Healthcare Facilities  [PDF - 419 KB]

 

Previously, in Vomiting Larry And His Aerosolized Norovirus, we looked at the physics involved in aerosolizing virus particles via projectile vomiting , while in  Norovirus: The Gift That Keeps On Giving, we looked at an incident involving a girl’s soccer team where 17 girls were exposed via a reusable grocery bag, likely contaminated from an airborne route.

 

Assuming more studies showing the aerosolized spread of noroviruses are published, infection control experts may need to revisit the use of some form of respiratory protection (N95, facemasks, etc.)  for HCWs caring for infected patients.

CID Journal: Under Utilization Of Antivirals For At Risk Flu Patients

 

# 8842

 

Between the frequent hyperbolic demonization of  influenza antivirals (see Daily Mail: Ministers blew £650MILLION on useless anti-flu drugs) by media critics of `Big Pharma’,  spurred on by repeated Cochrane group analyses that have found insufficient evidence that the drug reduces influenza complications, it probably comes as little surprise that many doctors – particularly in outpatient settings – tend to underutilize antiviral drugs, even for patients at the greatest risk for complications.

 

While well-respected, the Cochrane Group uses a very narrow (and some would say misguided) criteria for evaluating the effectiveness of antiviral drugs.  One that discards all but a handful of studies.

 

Last April, in Revisiting Tamiflu Efficacy (Again), I wrote at some length on the BMJ –  Cochrane Library review Neuraminidase inhibitors for preventing and treating influenza in healthy adults and children – that examined a subset of the scientific literature and cast doubt on its effectiveness in treating influenza.

 

While I too lamented the lack of solid, well mounted Randomized controlled trials (RCTs) proving the effectiveness of Oseltamivir (particularly in high risk patients, or with novel flu strains), I listed a number observational studies that strongly support the effectiveness of Oseltamivir.

 

A few days later, the CDC issued their own response. I’ve posted the link and some excerpts below.  Follow the link to read their rationale in its entirety.

 

CDC Recommendations for Influenza Antiviral Medications Remain Unchanged

April 10, 2014 -- CDC continues to recommend the use of the neuraminidase inhibitor antiviral drugs (oral oseltamivir and inhaled zanamivir) as an important adjunct to influenza vaccination in the treatment of influenza. CDC’s current influenza antiviral recommendations are available on the CDC website and are based on all available data, including the most recent Cochrane report, about the benefits of antiviral drugs in treating influenza.

(Continue . . .)

 

The CDC considers those a higher risk of influenza complications, and for whom they recommend antiviral treatment for suspected or confirmed influenza , to include:

• children aged younger than 2 years;
• adults aged 65 years and older;
• persons with chronic pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological (including sickle cell disease), metabolic disorders (including diabetes mellitus) or neurologic and neurodevelopment conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability [mental retardation], moderate to severe developmental delay, muscular dystrophy, or spinal cord injury);
• persons with immunosuppression, including that caused by medications or by HIV infection;
• women who are pregnant or postpartum (within 2 weeks after delivery);
• persons aged younger than 19 years who are receiving long-term aspirin therapy;
• American Indians/Alaska Natives;
• persons who are morbidly obese (i.e., BMI is 40 or greater); and
• residents of nursing homes and other chronic-care facilities.

But based on a new study, published this week in Clinical Infectious Diseases, antiviral drugs for these cohorts appear to be underutilized. Worse, patients were twice as likely to be prescribed antibiotics than antivirals for influenza.

Use of Influenza Antiviral Agents by Ambulatory Care Clinicians During the 2012–2013 Influenza Season

Fiona Havers1, Swathi Thaker2, Jessie R. Clippard2, Michael Jackson3, Huong Q. McLean4, Manjusha Gaglani5, Arnold S. Monto6, Richard K. Zimmerman7, Lisa Jackson3, Josh G. Petrie6, Mary Patricia Nowalk7, Krissy K. Moehling7, Brendan Flannery2, Mark G. Thompson2, and Alicia M. Fry2

Abstract

Background. Early antiviral treatment (≤2 days since illness onset) of influenza reduces the probability of influenza-associated complications. Early empiric antiviral treatment is recommended for those with suspected influenza at higher risk for influenza complications regardless of their illness severity. We describe antiviral receipt among outpatients with acute respiratory illness (ARI) and antibiotic receipt among patients with influenza.

Methods. We analyzed data from 5 sites in the US Influenza Vaccine Effectiveness Network Study during the 2012–2013 influenza season. Subjects were outpatients aged ≥6 months with ARI defined by cough of ≤7 days’ duration; all were tested for influenza by polymerase chain reaction (PCR). Medical history and prescription information were collected by medical and pharmacy records. Four sites collected prescribing data on 3 common antibiotics (amoxicillin-clavulanate, amoxicillin, and azithromycin).

Results. Of 6766 enrolled ARI patients, 509 (7.5%) received an antiviral prescription. Overall, 2366 (35%) had PCR-confirmed influenza; 355 (15%) of those received an antiviral prescription. Among 1021 ARI patients at high risk for influenza complications (eg, aged <2 years or ≥65 years or with ≥1 chronic medical condition) presenting to care ≤2 days from symptom onset, 195 (19%) were prescribed an antiviral medication. Among participants with PCR-confirmed influenza and antibiotic data, 540 of 1825 (30%) were prescribed 1 of 3 antibiotics; 297 of 1825 (16%) were prescribed antiviral medications.

Conclusions. Antiviral treatment was prescribed infrequently among outpatients with influenza for whom therapy would be most beneficial; in contrast, antibiotic prescribing was more frequent. Continued efforts to educate clinicians on appropriate antibiotic and antiviral use are essential to improve healthcare quality.

 

In an accompanying press release from the Infectious Diseases Society of America we get the following summary:

 

 

Findings suggest antivirals underprescribed for patients at risk for flu complications

Study also shows that antibiotics may have been prescribed unnecessarily

(EXCERPT)

Overall, only 19 percent of the patients at high risk for influenza-associated complications who saw a primary-care provider within two days of the onset of their symptoms received antiviral treatment. Among patients with laboratory-confirmed influenza, just 16 percent were prescribed antivirals. In contrast, 30 percent of these patients received one of the three antibiotics.

"Our results suggest that during 2012-'13, antiviral medications were underprescribed and antibiotics may have been inappropriately prescribed to a large proportion of outpatients with influenza," the authors wrote. "Continuing education on appropriate antibiotic and antiviral use is essential to improve health care quality."

While some of the antibiotics may have been appropriate for bacterial infections secondary to influenza, which is caused by a virus, it is likely most were unnecessary, potentially contributing to the growing problem of antibiotic resistance, the authors noted.

(Continue . . . )

 

CID Journal: H3N2v Outbreaks In United States – 2012

Credit CDC

 

# 7808

 

Swine are notoriously prone to influenza infections, and are viewed as potential `mixing vessels’ for flu viruses since they can be infected by swine, avian, and human flu strains. The most common swine flu strains are H1N1, H1N2, H3N1, H3N2, and H2N3.

 

Although predominantly affecting swine, on the rare occasions when they jump to humans, these strains are called variant viruses (e.g. H3N2v).

 

During 2012, a record number (300+) of swine variant infections were recorded in humans, mostly associated with swine exposure at county and state fairs across the Midwest. The concern with these variant flu infections, as with any novel flu, is that each new human exposure provides the virus another opportunity to better adapt to human physiology.

 

While sporadic human-to-human transmission of these viruses was strongly suspected last year, sustained community transmission did not appear to be occurring.   It is likely, however (see CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012)), that the number of confirmed cases under-represents the total number of variant flu infections that occur each year.

 

Today, another study appearing in the CID Journal, conducted by CDC and local Health department researchers, looks at 306 human variant flu infections reported across 10 states last year, and finds the vast majority appear to have contracted the virus from direct exposure to infected pigs, while only about 5% appeared to be the result of H-2-H transmission.

 

Outbreak of Variant Influenza A (H3N2v) Virus in the United States

Michael A. Jhung1, Scott Epperson1, Matthew Biggerstaff1, Donna Allen9, Amanda Balish1, Nathelia Barnes1, Amanda Beaudoin10, LaShondra Berman1, Sally Bidol7, Lenee Blanton1, David Blythe16, Lynnette Brammer1, Tiffany D'Mello1, Richard Danila8, William Davis1, Sietske de Fijter13, Mary DiOrio13, Lizette O. Durand2, Shannon Emery1, Brian Fowler13, Rebecca Garten1, Yoran Grant6, Adena Greenbaum2, Larisa Gubareva1, Fiona Havers2, Thomas Haupt14, Jennifer House9, Sherif Ibrahim15, Victoria Jiang1, Seema Jain1, Daniel Jernigan1, James Kazmierczak14, Alexander Klimov1, Stephen Lindstrom1, Allison Longenberger11, Paul Lucas4, Ruth Lynfield8, Meredith McMorrow1, Maria Moll11, Craig Morin8, Stephen Ostroff11, Shannon L. Page13, Sarah Y. Park12, Susan Peters7, Celia Quinn3, Carrie Reed1, Shawn Richards9, Joni Scheftel8, Owen Simwale11, Bo Shu1, Kenneth Soyemi4, Jill Stauffer9, Craig Steffens1, Su Su1, Lauren Torso11, Timothy M. Uyeki1, Sara Vetter8, Julie Villanueva1, Karen K. Wong2, Michael Shaw1, Joseph S. Bresee1, Nancy Cox1, and Lyn Finelli1

Abstract

Background. Variant influenza virus infections are rare but may have pandemic potential if person-to-person transmission is efficient. We describe the epidemiology of a multi-state outbreak of an influenza A H3N2v virus first identified in 2011.

Methods. We identified laboratory-confirmed cases of H3N2v and used a standard case report form to characterize illness and exposures. We considered illness to result from person-to-person H3N2v virus transmission if swine contact was not identified within 4 days prior to illness onset.

Results. From July 9—September 7, 2012, we identified 306 cases of H3N2v in ten states. The median age of all cases was 6 years. Commonly reported signs and symptoms included fever (98%), cough (84%), and fatigue (83%). Sixteen cases (5.2%) were hospitalized, and one fatal case was identified. The majority of cases reported agricultural fair attendance (93%) and/or contact with swine (95%) prior to illness. We identified 15 cases of possible person-to-person transmission of H3N2v virus. Viruses recovered from cases were 93% to 100% identical and similar to viruses recovered from previous cases of H3N2v. All H3N2v viruses examined were susceptible to the oseltamivir and zanamivir and resistant to adamantane antiviral medications.

Conclusion. In a large outbreak of variant influenza, the majority of cases reported exposures suggesting swine contact at an agricultural fair was a risk for H3N2v virus infection. We identified limited person-to-person H3N2v virus transmission, but found no evidence of efficient or sustained person-to-person transmission. Fair managers and attendees should be aware of the risk of swine-to-human transmission of influenza viruses in these settings.

 

Compared to last year, reports of swine variant infections this summer are greatly reduced.   Thus far, only 20 cases have been reported to the CDC (see Arkansas Reports Two H1N1v Infections for the latest reports). While we watch these flu strains for any signs they may be changing, for now, the threat to the public from these swine variant viruses appears low.

 

The CDC, in a statement on June 28th of 2013, offered this assessment on H3N2v:

 

CDC will continue to watch this virus closely to make sure there are no changes in the epidemiology of related human infections. That means watching for any changes in the severity of illness caused by infection with this virus and any signs that the virus is becoming more adept at spreading from person-to-person. Like all influenza viruses, it’s possible that mutations could occur that would allow this virus to become more severe or to spread more easily between people.

The risk of this virus triggering a full-blown pandemic is considered relatively low, however, because serology studies have suggested that significant numbers of adults have some existing immunity against this virus. Children younger than about 10 years old, however, have little to no immunity against H3N2v virus. Given this, a more likely scenario if H3N2v were to become more transmissible among people would be localized outbreaks in pockets of the population that do not have immunity against this virus, for example, in day care or school settings.

A few of my recent blogs on Swine variant influenza include:

 

Study: Novel & Variant Swine Influenzas In Korean Pigs

CDC Updates H3N2v County & State Fair Advice

CDC HAN Advisory On H3N2v

And for more information, you may wish to visit the CDC’s Variant (Swine Origin) Influenza Viruses in Humans webpage, or visit these related links.

 

• Key Facts about Human Infections with Variant Viruses (Swine Origin Influenza Viruses in Humans)
• Reported Infections with Variant Influenza Viruses in the United States since 2005
• Influenza A (H3N2) Variant Virus
• What People Who Raise Pigs Need To Know About Influenza (Flu)
• Reports of Human Infections with Variant Viruses

CID Journal: Estimates Of Human Infection From H3N2v (Jul 2011-Apr 2012)

 

Credit CDC

 

 

# 7435

 

 

In my last post (see CID Journal: Lessons From The `First Wave’ Of H3N2v) I recounted the history of the `first wave’ of the H3N2v swine variant virus (July 2011-Apr 2012) as part of a lead up to a series of articles just published in a supplement to the journal Clinical Infectious Diseases.

 

While only 13 human infections were detected during this 9 month time span, it is considered more than probable that a significant number of cases went undetected.

 

We know with practically every infectious disease you can name, that surveillance and testing only picks up a fraction of the total number of cases.  The proverbial `tip of the iceberg’ or in the case of the graphic below, the `top of the pyramid’. 

 

Credit CDC 

 

As an example, last year the CDC was notified of 5,674 cases of West Nile virus disease in people, including 286 deaths. But the actual number of WNV infections (including mild & asymptomatic cases) may have been well over 100,000.

 

Similarly, we don’t actually know how many people contract, or even die from, influenza each year in the United States. With all of these diseases, the number of cases each year must be estimated, based on available surveillance and testing and mathematical modeling.

 

Which brings us to a study that attempts to extrapolate - using models developed during the opening months of the 2009 H1N1 pandemic - how many undetected cases of H3N2v may have occurred during this first wave (July 2011 – April 2012) when only 13 cases were confirmed.

 

Their results – that more than 2,000 human infections from H3N2v may have occurred during this time -  I suspect, will surprise a lot of people.

 

 

Estimates of the Number of Human Infections With Influenza A(H3N2) Variant Virus, United States, August 2011–April 2012

Matthew Biggerstaff, Carrie Reed, Scott Epperson, Michael A. Jhung, Manoj Gambhir, Joseph S. Bresee, Daniel B. Jernigan, David L. Swerdlow, and Lyn Finelli

Background. Thirteen human infections with an influenza A(H3N2) variant (H3N2v) virus containing a combination of gene segments not previously associated with human illness were identified in the United States from August 2011 to April 2012. Because laboratory confirmation of influenza virus infection is only performed for a minority of ill persons and routine clinical tests may not identify H3N2v virus, the count of laboratory-confirmed H3N2v virus infections underestimates the true burden of illness.

 

<SNIP  Methods>

Results. We estimate that the median multiplier for children was 200 (90% range, 115–369) and for adults was 255 (90% range, 152–479) and that 2055 (90% range, 1187–3800) illnesses from H3N2v virus infections may have occurred from August 2011 to April 2012, suggesting that the new virus was more widespread than previously thought.

 

 

Their estimates range from just under 1,200 cases to nearly 4,000 for this `first wave’. 

The `second wave’ began in late June 2012, and ran well into the fall, resulted in more than 300 confirmed cases. This study strongly suggests that those represented but a tiny fraction of the `true’ number of infections last summer.

 

Granted, the surveillance picture during the second wave – once the news broke that scores of people attending county & state fairs had contracted the virus – likely changed from during the first wave.

 

My guess is that these multipliers may need a bit of tweaking for use with the second wave, to account for more robust surveillance and testing that was put into place. 

 

But even so, the number of undetected cases last summer was likely many-fold greater than the 300 confirmed infections turned up by surveillance.

 

This past week, we learned of four new cases (see CDC FluView Update On H3N2v Cases) linked to attendance at a county fair in Indiana.

 

Given the prevalence of the H3N2v virus in swine, and the increased potential for exposure over county & state fair season (running from June-November), it seems likely we’ll be hearing a good deal more about this variant flu virus in the coming months.

 

Despite these numbers, and apparent limited human-to-human transmission of this virus, this strain has not yet managed to spread efficiently in the community.

 

The CDC maintains an H3N2v and You FAQ page, and offers the following advice for fairgoers and exhibitors.

 

Preventive Actions

CDC Recommendations For People At High Risk:

• If you are at high risk of serious flu complications and are going to a fair where pigs will be present, avoid pigs and swine barns at the fair this year. This includes children younger than 5 years, people 65 years and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).

If you are not at high risk, take these precautions:

• Don’t take food or drink into pig areas; don’t eat, drink or put anything in your mouth in pig areas.
• Don’t take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
• Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.
• Avoid close contact with pigs that look or act ill.
• Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes minimizing contact with pigs and wearing personal protective equipment like protective clothing, gloves and masks that cover your mouth and nose when contact is required.
• To further reduce the risk of infection, minimize contact with pigs and swine barns.

 

CID Journal: Lessons From The `First Wave’ Of H3N2v

CID H3N2v Supplement

# 7435

 

Between 2005 and the end of 2010, the CDC  documented 19 human infections by swine origin influenza viruses (SOIV) across the United States, 12 of which were trH1N1 viruses, 6 were trH3N2, and 1 was trH1N2.

In 2011 a new strain of swine influenza  - originally dubbed trH3N2 but renamed H3N2v (swine variant influenza) in late 2011 – was discovered to have evolved in pigs.

 

What made this virus different from the earlier trH3N2 novel strains was that it was a reassortant swine H3N2 which had acquired the matrix (M) gene from the 2009 H1N1 pandemic virus.

 

Reassortant H3N2 virus detected in Pennsylvania & Indiana – Source CDC

 

We first heard about this new strain on Sept. 2nd, 2011, via an early release from the CDC’s MMWR.

 

That report described two young children – one in Indiana and another in Pennsylvania - who were infected by a new swine-origin H3N2 virus (see Swine-Origin Influenza A (H3N2) Virus Infection in Two Children --- Indiana and Pennsylvania, July--August 2011).

 

While these first two cases first appeared to be one-off, dead end transmissions, it was only a few days later that Pennsylvania Reported 2 More Novel Flu Cases.

 

All three cases in Pennsylvania were linked to the Washington County Agricultural Fair during the week of Aug. 13-20, 2011.

 

On September 9th, 2011 the CDC updated their SOIV (Swine Origin Influenza Virus) page (see CDC Update On Recent Novel Swine Flu Cases), acknowledging the possibility that limited human-to-human transmission of this trH3N2 virus might be occurring.

 

The CDC’s MMWR on November 23rd detailed the Iowa cases in a dispatch called Limited Human-to-Human Transmission of Novel Influenza A (H3N2) Virus — Iowa, November 2011.

 

By now, it was pretty apparent that this swine H3N2 virus had a greater affinity to human hosts than most of the other SOIVs we’d seen in the past (excluding the 2009 H1N1pdm virus).

 

 

Near the end of November the USDA reported they had detected a number of reassortant H3N2 viruses in swine, including 8 that displayed the 2009 H1N1 matrix (M) gene (see CIDRAP article New details emerge in novel H3N2 reports).

 

And in early December we learned that the CDC was Developing A trH3N2 Seed Vaccine . . . just in case this virus continued to spread.

 

December also saw a few more scattered cases in Minnesota and West Virginia, and the virus was given a new name WHO/FAO/OIE: Call It A(H3N2)v.  By the end of the year, there were an even dozen cases reported around the country.

 

By April, 2012 a total of 13 human infections with this new strain had been detected in the United States. The summer of 2012 would see a major escalation in cases (more than 300), but for the next few months at least, the `first wave’ was over.

 

All of which serves as prelude to a series of articles that appear in a July Clinical Infectious Diseases Supplement (abstracts & excerpts available, full text behind a subscription / pay wall) called:

 

The Emergence of Influenza A (H3N2)v Virus: What We Learned From the First Wave, July 2011–April 2012

 

Volume 57 suppl 1 July 15, 2013

The Emergence of Influenza A (H3N2)v Virus: What We Learned From the First Wave

Clin Infect Dis. (2013) 57 (suppl 1): S1-S3 doi:10.1093/cid/cit324

Lyn Finelli and David L. Swerdlow

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Human Infections With Influenza A(H3N2) Variant Virus in the United States, 2011–2012

Clin Infect Dis. (2013) 57 (suppl 1): S4-S11 doi:10.1093/cid/cit272

Scott Epperson, Michael Jhung, Shawn Richards, Patricia Quinlisk, Lauren Ball, Mària Moll, Rachelle Boulton, Loretta Haddy, Matthew Biggerstaff, Lynnette Brammer, Susan Trock, Erin Burns, Thomas Gomez, Karen K. Wong, Jackie Katz, Stephen Lindstrom, Alexander Klimov, Joseph S. Bresee, Daniel B. Jernigan, Nancy Cox, Lyn Finelli, and for the Influenza A (H3N2)v Virus Investigation Team

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Estimates of the Number of Human Infections With Influenza A(H3N2) Variant Virus, United States, August 2011–April 2012

Clin Infect Dis. (2013) 57 (suppl 1): S12-S15 doi:10.1093/cid/cit273

Matthew Biggerstaff, Carrie Reed, Scott Epperson, Michael A. Jhung, Manoj Gambhir, Joseph S. Bresee, Daniel B. Jernigan, David L. Swerdlow, and Lyn Finelli

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Transmissibility of Variant Influenza From Swine to Humans: A Modeling Approach

Clin Infect Dis. (2013) 57 (suppl 1): S16-S22 doi:10.1093/cid/cit303

Karen K. Wong, Manoj Gambhir, Lyn Finelli, David L. Swerdlow, Stephen Ostroff, and Carrie Reed

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Multiple Contributory Factors to the Age Distribution of Disease Cases: A Modeling Study in the Context of Influenza A(H3N2v)

Clin Infect Dis. (2013) 57 (suppl 1): S23-S27 doi:10.1093/cid/cit298

Manoj Gambhir, David L. Swerdlow, Lyn Finelli, Maria D. Van Kerkhove, Matthew Biggerstaff, Simon Cauchemez, and Neil M. Ferguson

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In my next post, I’ll take a closer look at a couple of these reports.