Clinical Virology Programs

Are International Students at Greater Risk for the Novel H1N1 Flu Virus in the U.S.?

Question: Are international students at greater risk for flu strains circulating in the U.S. population?

Answer: No. Novel flu has been circulating pretty much worldwide since April-May 2009. Flu viruses are not isolated geographically especially since international travel is relatively common.

2009 Flu Facts

Normally, up to 3 influenza types circulate worldwide each respiratory virus season. They are now known as “seasonal” influenza A H1N1, influenza A H3N2, and influenza B. Vaccine is prepared for the U.S. each spring/summer using what appear to be the dominant serotypes according to southern hemisphere surveillance. Vaccine is usually available to us in the fall. BHS is using FluLaval, which this season contains influenza virus hemagglutinin (a piece of the outside part of the virus of each of the following 3 strains: A/Brisbane/59/2007 (H1N1), A/Uruguay/716/2007 (H3N2) and B/Brisbane/60/2008. Vaccine is administered in a single 0.5 mL dose into a muscle, usually in the upper arm.

The 2009-2010 season differs from previous ones in that the swine origin novel A H1N1 (we’ll call it “novel” H1N1) flu virus has been circulating in human populations since last winter. This means that we could have 4 flu viruses around this winter. Because novel H1N1 is substantially different than the current seasonal A H1N1, the WHO declared that it represented a “shift” in influenza genetics and thus has the possibility of producing a pandemic because the bulk of the population hasn’t seen a virus like it before. A pandemic raises concerns that intense person-to-person or person-to-animal-to-person spread could result in a mutation that renders the virus more virulent than regular seasonal flu.

At present, the reality is that novel H1N1 is highly contagious but no more virulent—probably less so—than seasonal flu. Resistance to the antiviral neuraminidase inhibitor (NI) drug oseltamivir (tamiflu) is rare. Resistance to inhalational zanamivir (relenza) has just been reported but must still be considered rare.

Risk groups for more severe seasonal and novel H1N1 influenza are those with:

1. Underlying medical conditions (such as heart or kidney disease, asthma or other chronic lung disease, diabetes, neuromuscular or neurological disorders, or a suppressed immune system)
2. Pregnant women
3. Children under 5 years (especially those under age 2)
4. Persons 65 years and older

Although few University students are in the above risk groups, Clinical Virology Programs recommends the flu vaccine for all students to prevent days lost from school and to protect others. If enough of us are immunized, the campus will have “herd” immunity, which means that the virus has trouble finding a susceptible person to spread to.

National data of novel H1N1 cases from the spring of this year show that children less than 5 years old had the highest hospitalization rate. In Minnesota, the rate of hospitalization from novel H1N1 influenza among children less than 5 years old was twice the rate of children 5 – 12 years old.

Diagnosis is made by rapid antigen detection, culture and/or PCR. We have both rapid antigen and culture available in the Clinical Virology Lab at the U and are working to acquire an approved PCR assay this season.

• Prevention is the cornerstone of influenza control. The first and best line of defense is annual seasonal
• Influenza immunization—available now. Novel flu immunization is recommended as soon as available. Best guess, early October. Antiviral prophylaxis with either NI is also effective, but widespread prophylactic use of these compounds could promote viral resistance. We recommend these vaccines for everyone except those few persons who are allergic to components of the vaccine.
• Treatment using either of the NIs works, but is most effective when started within 48h of symptoms. These are prescription drugs.
• Good hygiene. Wash your hands as often as possible. It seems funny, but try not to pick your nose or rub your eyes. Cover your coughs and sneezes.