Overview / History

Influenza A H3N2 is a strain of flu viruses which is capable of circulating widely among humans and has the potential to cause pandemics. It is also prevalent among birds and animals. There are seasonal variations in transmission of the virus. The strain can affect people in all age groups and is capable of causing severe illness, especially in high-risk groups. The strain is included in seasonal influenza vaccines and annual vaccination with this vaccine helps in preventing infection.

Mode of spread

Coughing / Sneezing

Animals

Transmission

Flu viruses, including H3N2 spread through the droplets an infected person generates when they cough, sneeze or talk. People who are in close contact (within 1 to 2 metres) can be infected when they inhale the droplets directly, or touch them with their hands and then transfer them to their eyes, nose or mouth.

Children younger than age 2 years, adults aged 65 years or older, pregnant women, and people of any age with certain medical conditions, such as chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes), or weakened immune systems are at higher risk of the disease and are categorised as high-risk group.

Symptoms

H3N2 causes fever, cough, headache, bodyache, malaise, sore throat and runny nose. Most cases are mild and patients recover on their own within a week. However cough may be prolonged. Some people may need treatment with antiviral medications. Severe cases occur among people in the high-risk groups and may require hopsitalisation.

Diagnosis

Flu is diagnosed on the basis of signs and symptoms. The strain H3N2 can be confirmed through specialised lab tests.

Treatment

Because it is a viral illness, H3N2 does not respond to antibiotics. Flu can generally be treated with antiviral medications, which are most effective when given very soon after symptoms begin. Antiviral treatment is not needed in all cases. Treatment decisions are made on an individual assessment by a person's doctor or other medical provider. Many choose to alleviate their symptoms with over-the-counter (non-prescription) medications.

Vaccination

H3N2 is included in the seasonal influenza vaccine. Annual vaccination is required.

Prevention

The most efficient way to prevent H3N2 is to be vaccinated against it. Vaccination needs to be repeated annually, as flu viruses change rapidly. One year's vaccine is not effective against the viruses that will circulate widely the next year. Flu vaccines usually contain two or three strains of influenza virus that are expected to be most prevalent in the upcoming flu season. Vaccination is recommended for:

• International travellers.
• Anyone over 6 months of age who wants to avoid getting the flu.
• People at high risk for severe infections.
• Women who will be in the second or third trimester of pregnancy during the influenza season. Vaccination is considered safe throughout pregnancy, but most medical providers usually avoid vaccinating women during the first trimester.

• Maintain good personal hygiene.
• Wash your hands frequently. Carry a hand sanitizer for use when soap and water are not readily available.
• Avoid touching your face.
• Avoid people who are obviously sick.
• Ensure all routine vaccinations are up to date. This includes pneumococcal vaccination for some groups of people.

Risk to travellers

Influenza is one of the most common vaccine-preventable diseases among travellers. To reduce the chances of developing H3N2, all travellers should be vaccinated annually. The risk of exposure to influenza depends on the time of year and destination.

• In the Northern Hemisphere, the flu season generally ranges from November through March.
• In the Southern Hemisphere, most activity occurs from April through September.
• In the tropics, the risk of exposure exists throughout the year.

Further Reading