A 8 year old boy in Cumberland County Maine has been infected with the same H3N2 influenza virus that has previously infected three people in Pennsylvania and one in Indiana. This virus is apparently circulating in pigs in the US.
The people in Indiana and Pennsylvania were infected in late July and August 2011. The 8 year old boy in Maine became ill in early October 2011. He is reported to have been in close proximity to pigs at an agricultural fair. There is disagreement regarding the severity of her symptoms. Although most reports suggest that she was not hospitalised, one media source says that she was.
From Kennebec Journal, October 21, 2011
The Maine Center for Disease Control and Prevention is investigating a new type of swine flu that sickened a child in Cumberland County.
The agency has not provided any more details about who was affected or where, but said it is an isolated event in Maine and has not been detected in people who had contact with the child. The child was hospitalized and is recovering, it said.
The Maine CDC is recommending the following precautions for health care providers:
- Maintain a heightened awareness for influenza-like illness (ILI) defined as fever greater than 100° with cough or sore throat, in the absence of another known cause.
- Consider influenza testing by PCR for:
- patients with ILI with recent exposure to pigs.
- patients with ILI who are hospitalized,
- patients with ILI who have died,
- patients where a diagnosis of influenza would affect clinical care, infection control, or management of contacts.
The virus that infected the boy in Maine, the three people in Pennsylvania and the child in Indiana has a complex ancestry. The HA and NA genomic segments are originally derived from humans, but are different from those currently circulating in H3N2 human flu viruses. The PB1 genomic segment originated in humans. The PB2 and PA genomic segments originated in birds. The NP and NS genomic segments originated in pigs. The Matrix or M segment, came from the human 2009 pandemic H1N1 virus, apparently as a result of reassortment between a virus that has been circultating in pigs and the pandemic 2009 H1N1 virus.
Five individuals have now been reported to be infected with this virus within a relatively short time. Pig to human transmission is likely, although it is not know if this was due to direct contact or respiratory spread. Although sustained human to human spread of the new virus has not been reported, this could happen at any time. The virus could change further as result of reassortment, recombination or mutation.
Swine-Origin Influenza A (H3N2) Virus Infection in Two Children — Indiana and Pennsylvania, July–August 2011
Morbidity and Mortality Weekly Report (MMWR), September 9, 2011/60(35);1213-1215
[corrected age and gender of child based on new information, October 24, 2011. Hat-tip, Dr. Niman]