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European swine flu may target immunocompromised
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An Italian man who tested positive for swine flu may have contracted the virus in part because he was immunocompromised, according to a case study published in Emerging Infectious Diseases.
“Zoonotic influenza A infections in humans caused by swine influenza viruses (SIVs) have been infrequently reported in Europe, even though at least 19% of occupationally exposed humans, such as pig farmers, slaughterers, and veterinarians have SIV antibodies,” Fausto Baldanti, MD, of the virology and immunology department at Fondazione IRCCS Policlinico San Matteo in Pavia, Italy, and colleagues wrote. “However, because the infection is clinically mild in most cases, its frequency might be underdiagnosed in humans.
“On the basis that none of the patient’s family members and co-workers showed respiratory infection, we can hypothesize that immune impairment of the patient could have favored the zoonotic transmission of the SIV strain.”
The patient, aged 67 years, was undergoing his eighth cycle of chemotherapy in January 2014 when he was nasally swabbed and tested by real-time reverse transcription PCR (RT-PCR) and PCR for mild respiratory symptoms (ie, fever, cough and cold), the researchers wrote.
After test results came back positive for influenza A infection but failed to identify the strain as a human or avian virus, the clinical sample was inoculated onto a mixed-cell monolayer. This yielded positive results for swine virus strain A/Pavia/07/2014(H3N2), according to the researchers. The man had recently spent several weeks on a pig farm and had contact with pigs as well as family members. Later in January, the patient was tested via nasal swab, and no virus was detected even though he did not receive treatment for his respiratory illness.
The pigs were tested by RT-PCR, and results came back negative, according to the researchers, perhaps because 2 months had elapsed between the onset of respiratory symptoms and testing. When hemagglutination-inhibition testing was implemented, all 29 tested samples were positive for H3 antibodies, and 15 of the samples also tested positive for A(H1N1).
“The swine influenza A(H3N2) viruses present in Europe since 1984 resulted from a genomic reassortment between human-like swine H3N2 viruses and avian-like swine H1N1 viruses,” the researchers wrote. “In agreement with previous observations, the European H3N2 swine viruses seem to cause a benign disease with mild influenza-like symptoms in humans.
“Surveillance of circulating SIVs and monitoring of occupationally exposed workers are two important tools to prevent the spread of potential pandemic viruses.” – by David Jwanier
Disclosure: The researchers report no relevant financial disclosures.
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