Avian Flu Diary: Hong Kong: A Severe Pediatric Case Of Influenza C

Credit NIAID

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When it comes to flu, Influenza A - due to its ability to produce severe illness and to rapidly mutate and reassort with other influenza A viruses - is viewed as the biggest human health threat. Influenza B, while less apt to make big evolutionary leaps, comes in second due to its ability to cause serious illness (see Influenza B: A Virus Not To Be Underestimated).

Influenza C - which is rarely tested for - doesn't get a lot of attention. And recently discovered Influenza D, even less so.

From the CDC's website (bolding mine):

Types of Influenza Viruses

There are four types of influenza viruses: A, B, C and D. Human influenza A and B viruses cause seasonal epidemics of disease almost every winter in the United States. The emergence of a new and very different influenza A virus to infect people can cause an influenza pandemic. Influenza type C infections generally cause a mild respiratory illness and are not thought to cause epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

But there are always exceptions to any rule. A study published in Clinical Infectious Diseases (2017) found:

Detection of Influenza C Viruses Among Outpatients and Patients Hospitalized for Severe Acute Respiratory Infection, Minnesota, 2013-2016.

Thielen BK1,2, Friedlander H3, Bistodeau S3, Shu B4, Lynch B4, Martin K3, Bye E3, Como-Sabetti K3, Boxrud D3, Strain AK3, Chaves SS4, Steffens A4, Fowlkes AL4, Lindstrom S4, Lynfield R3.

Conclusion: We found seasonal circulation of influenza C with year-to-year variability. Detection was most frequent among young children but occurred in all ages. Some cases that were positive for influenza C, particularly those with comorbid conditions, had severe disease, suggesting a need for further study of the role of influenza C virus in the pathogenesis of respiratory disease.

Although it is still pretty rare, Hong Kong's CHP today reports on a severe pediatric case of Influenza C, which presented with transient encephalopathy.

CHP investigates case of severe paediatric influenza C infection

The Centre for Health Protection (CHP) of the Department of Health is today (December 18) investigating a case of severe paediatric influenza C infection and reminded the community to heighten vigilance against influenza.

The case involves a 7-year-old boy with good past health, who has presented with a fever, cough and headache since December 3, and convulsions on December 13. He was taken to the Accident and Emergency Department at Queen Elizabeth Hospital for medical advice on the same day and was admitted. He was subsequently transferred to the Paediatric Intensive Care Unit at the hospital for further management.

His nasopharyngeal swab tested positive for influenza C virus upon laboratory testing. The clinical diagnosis was influenza C infection complicated with transient encephalopathy. He is now in stable condition.

Initial enquiries revealed that the patient had not received a seasonal influenza vaccination (SIV) for this season and had no travel history during the incubation period. His home contacts have remained asymptomatic so far.

The CHP's investigations are ongoing.

A spokesman for the CHP said, "Although the overall local seasonal influenza activity is currently at a low level, members of the public are advised to receive an SIV in a timely manner to better protect themselves in the coming winter influenza season against influenza A and B infections. Particularly, children, the elderly and those with underlying illnesses are urged to get vaccinated as early as possible as it takes about two weeks for antibodies to develop in the body after vaccination."

The 2019/20 seasonal influenza vaccination programmes, including the Vaccination Subsidy Scheme and the Government Vaccination Programme, have been launched. As well, the SIV school outreach has been regularised to allow all primary schools to join, and has been extended to kindergartens, child care centres and kindergarten-cum-child care centres as a pilot.

"Influenza can cause serious illnesses in high-risk individuals and even healthy persons. Given that influenza vaccines are safe and effective, all persons aged 6 months or above, except those with known contraindications, are recommended to receive an SIV for personal protection. Vaccinations among family members is key to protecting their personal and family health," the spokesman said.

The public should maintain good personal and environmental hygiene for protection against influenza and other respiratory illnesses:

Receive an SIV for personal protection;

Wash hands with liquid soap and water properly whenever possibly contaminated;

When hands are not visibly soiled, clean them with 70 to 80 per cent alcohol-based handrub as an effective alternative;

Wash or clean hands frequently, especially before touching the mouth, nose or eyes, or after touching public installations such as handrails or door knobs;

Cover the nose and mouth when sneezing or coughing, and wash hands thoroughly afterwards;

Dispose of soiled tissue paper properly in a lidded rubbish bin;

Put on a surgical mask when respiratory symptoms develop;

Maintain good indoor ventilation;

Avoid going to crowded or poorly ventilated public places; high-risk individuals may consider putting on surgical masks when staying in such places; and

Maintain a balanced diet, exercise regularly, take adequate rest, do not smoke and avoid overstress.

The public may visit the CHP's influenza page and weekly Flu Express for more information.