H3N2 variant influenza AMaine, 2011Sara Robinson, MPH

EpidemiologistMaine Center for Disease Control and

Prevention

H3N2 in Swine and Humans

• H3N2 began circulating in swine in the U.S. in 1998, introduced by humans

• Currently circulating swine flu H3N2 viruses are different from human H3N2s.

• Sporadic human infections with SI do occur usually in people exposed to swine at fairs or farm workers.

• Limited human-to-human spread.

Variant influenza A (H3N2v)

• This particular virus carries the M gene from the 2009 H1N1 virus.

• This virus first reported in a human from Indiana in July 2011.

• 12 total cases reported in 2011– 2 in Indiana -3 in Iowa– 3 in Pennsylvania -2 in West Virginia– 2 in Maine

• 1 case reported to date in 2012, in Utah

Case A – lab information

• 10/14/2011 – Maine’s Health and Environmental Testing Laboratory (HETL) notified Maine CDC of an influenza A positive sample– Positive for H3, and the swine component of H1N1– Sample collected as part of an enhanced surveillance

initiative in Maine• Sample forwarded to federal CDC for

confirmation – confirmed as swine-origin triple reassortant influenza A(H3N2) on Monday 10/17/2011

Case A – Epi info

• 7 yo M with symptom onset of fever, cough, headache, sore throat and myalgia on 10/07/2011

• Seen at providers office 10/10/2011– Rapid influenza A positive– Sample taken for PCR testing (enhanced surveillance)

• Underlying conditions: asthma• No 2011-2012 season influenza vaccine (vaccinated in 2010)• Treated with Tamiflu• Case A visited agricultural fair multiple days and spent time

in the swine barn– No known direct contact with pigs

Agricultural Fair

• New swine barn at the fair with over 150 swine exhibited.

• 160,000 + attend this fair and many visit the swine exhibit (probably the only time that many people SEE a pig).

• Ten swine exhibitors at the fair from NH, MA and ME.• Four pig scrambles held throughout the fair week, 10

baby pigs per scramble, 10-14 2nd- 3rd graders in each event.

Agricultural and Epi Response

• Investigation revealed there were some sick pigs at the fair and one of the scramble pigs died.

• All farms were visited and all pigs examined by a regulatory veterinarian.

• USDA guidelines only recommend testing swine with influenza-like illness. Samples submitted from two farms, both negative.

• Numerous people with ILI identified through farm contacts, all interviewed, several tested, all negative.

Epi Response

• Sent health alert state wide• Notified area providers and hospitals• Encouraged PCR testing (notified area

commercial labs)• Contacted case’s school to enhance surveillance• Contacted schools that participated in pig

scramble to enhance surveillance– Several ill individuals identified, all tested negative

for influenza

Case B – lab information

• 10/28/2011 –HETL notified Maine CDC of an influenza A positive sample– Positive for H3– High CT count

• Provider noted swine contact on submission form, sent for confirmation because of epi link

• Sample forwarded to federal CDC for confirmation – confirmed as swine-origin triple reassortant influenza A(H3N2) on Monday 10/31/2011

Case B – epi information

• 8 yo M with symptom onset of fever, myalgia, and runny nose on 10/22/2011

• Seen at providers office 10/24/2011– Sample taken for PCR testing

• No 2011-2012 season influenza vaccine (vaccinated in 2010)

• Case A visited agricultural fair multiple days and participated in a pig scramble, winning one of the pigs

• Case helped take care of pigs at family friend’s farm

Secondary Response

• Contacted farm where pig was located – This farm had been visited after the 1st case was

identified• 2 secondary farms bought pigs from this farm– Both were visited, ill swine swabbed

• One pig was PCR positive, but unable to isolate virus – inconclusive results

• Contacted family– Sibling was ill with ILI, but influenza testing was

negative, viral culture also negative

Timeline

Fair

10/7

Swine samples collected

Swine samples collected

Health Alert (human and

animal)

Lab confirmation Case B

Lab confirmationCase A

Case B onsetCase A onset

10/2 10/9

10/17

10/22

10/27

10/19

10/31

11/9No additional human cases detected

Conclusions

• Both cases had documented swine exposure• No human to human transmission identified• Plenty of sick pigs, and sick humans but

difficult to get positive influenza tests• Increased awareness important• Importance of PCR testing• Importance of collaboration with the lab, and

with the Department of Agriculture

Acknowledgements• Maine CDC

– Stephen Sears– Lauren Ball– Kate Colby– Heidi Mallis– Lori Webber– Brian Bernier

• USDA– Chip Ridky– Frederic Cantor– Nicole Giguere– Bill Smith

• Department of Agriculture– Don Hoenig– Beth McEvoy

• New Hampshire– Stephen Crawford– John Dreisig

• Massachusetts– Lorraine O’Connor

• Federal CDC