Influenza A (H1N2) virus variant – Brazil

On June 22, 2020, the International Health Insurance Contact Point (IHR) in Brazil shared a preliminary report with the Pan American Health Organization, the WHO Regional Office for America, on human infection with Influenza virus variant A (H1N2) (A (H1N2) v), According to the report, the patient, a 22-year-old woman, without comorbidity, worked in a pig slaughterhouse in Ibiporã municipality, Paraná state, and developed a flu-like illness on April 12, 2020. The patient initially sought medical care on April 14, and 16. April, a respiratory sample was obtained as part of routine surveillance activities. The patient was treated with oseltamivir, was not hospitalized and recovered.

A real-time RT-PCR test, conducted in the Public Health Laboratory, identified a non-subtype influenza A virus. In May 2020, the sample was forwarded to the Laboratory for Respiratory Viruses and Measles, Oswaldo Cruz Institute (FIOCRUZ by acronym in Portuguese), national reference laboratory for influenza, in Rio de Janeiro. On June 22, by genetic sequencing, this virus was characterized as influenza A (H1N2) v virus.

Public health response

Further genetic and phenotypic characterization of the virus by the patient is ongoing.

On June 26, 2020, local authorities launched a retrospective and prospective investigation at the slaughterhouse in Ibiporã municipality and other municipalities where slaughterhouse workers live. According to a preliminary epidemiological study, another individual who also worked at the slaughterhouse developed respiratory symptoms in the same time frame as the confirmed case, but no sample was collected from this person. No other suspicious cases were identified among the contacts of the confirmed case.

Data from virological characterization and epidemiological examination, in particular the probable source of the patient exposed to the virus and the identification of any additional cases in humans, include a risk assessment of the likelihood of transmission from person to person.

WHO risk assessment

To date, 26 cases of influenza A (H1N2) v have been reported to the WHO since 2005, including two from Brazil. Most cases had a mild illness, and there is no evidence of transmission from person to person.

Swine flu viruses circulate in the pig population in many regions of the world. Depending on the geographical location, the genetic characteristics of these viruses differ. Most human cases are due to exposure to swine flu viruses through contact with infected pigs or a contaminated environment. As these viruses continue to be detected in the pig population worldwide, further cases in humans can be expected.

WHO advice

Due to the ever-evolving nature of influenza viruses, the WHO continues to emphasize the importance of global surveillance to detect virological, epidemiological and clinical changes associated with circulating influenza viruses that may affect human (or animal) health and share such changes in a timely manner to assess risk.

All human infections caused by a new subtype of influenza are subject to notification under this system International Health Regulations (IHR) and IHR (2005) States Parties must immediately notify the WHO of any laboratory-confirmed case of recent human infection caused by influenza A virus that could cause a pandemic. Evidence of disease is not required for this report .

In case of confirmed or suspected human infection caused by a new influenza virus with pandemic potential, including a variant virus, a thorough epidemiological investigation (even pending confirmatory laboratory results) of animal exposure history, travel and contact search should be conducted. The epidemiological investigation should include early identification of unusual respiratory events that could signal the transmission of the new virus from person to person, and clinical samples collected from the time and place where the case occurred should be tested and sent to the WHO Cooperation Center for further characterization,

General hygiene measures should be followed, such as regular hand washing before and after touching animals and avoiding contact with sick animals. The WHO does not recommend any special measures for travelers. Who does not advise a special inspection at the points of entry with regard to this event, nor does it recommend that any restrictions on travel and trade apply.