Many HIV-infected people will develop influenza during a flu season, even if they have been vaccinated against the disease, say Canadian researchers.
They say more needs to be done to educate people living with HIV about signs of the disease to ensure they get rapid access to antiviral treatments like Tamiflu (oseltamivir), especially in the event of a flu pandemic.
There have been very few studies on viral diseases of the upper respiratory tract since the widespread use of antiretroviral therapy (ART).
So researchers at the McGill University Health Centre in Montreal looked at 50 HIV-infected patients who presented with fever and respiratory symptoms during the flu seasons from 2003/4 to 2005/6. They took swabs from each patient’s nose and throat and cultured them for common respiratory viruses.
They found evidence of a viral infection in 42% of patients - even though 76% of all the patients had received a flu jab that season.
Ten patients had influenza A - the most severe of the two types. A further ten had the milder influenza B strain.
Despite the fact that many were suffering a viral – not bacterial - infection, 70% had been prescribed antibiotics. None of the patients had been given specific anti-flu treatments such as Tamiflu (Klein 2007).
The authors say this is the first research to suggest there are very high levels of both influenza A and B among HIV-infected people taking ART despite the fact that most had received a flu jab.
On average patients had taken three days to present to the clinic after symptoms first appeared. Drugs like Tamiflu should ideally be given within 48 hours of symptom onset, and the researchers stress that both patients and healthcare providers need to be made more aware of how common flu is among HIV-infected people so they can get rapid access to treatment.
HIV outpatient centres should also have access to rapid testing of respiratory swabs to speed up diagnosis.
A surprising finding was how common influenza B was in this group of patients when in the general Canadian population the proportion of people with the more severe influenza A ranged from 81% to 99% in the three seasons studied.
The researchers say there is no obvious reason for this difference other than the possibility that HIV-infected people who developed flu were clustered in specific areas.
Finally, they point out that this susceptibility to flu among vaccinated HIV-infected people raises serious concerns about how prepared health services are for the predicted flu pandemic.
HIV-infected people may be both particularly at risk and act as a potential reservoir for flu infection in the general population. Serious thought needs to be given to targeting HIV-infected people for antiviral treatment in the event of a pandemic.
Another just published study has suggested that Canadian healthcare providers had done very well to ensure that 76% of the HIV-infected individuals received flu vaccination.
A US study from 1990 to 2002 suggests that although the number of HIV-infected people getting a flu jab increased year on year, it had still only reached 42% by 2002, well under the recommended rate of 60% for all high risk groups (Gallagher 2007).
Klein MB et al. Influenza infection is a primary cause of febrile respiratory illness in HIV-infected adults, despite vaccination. Clinical Infectious Diseases 45: 234-240, 2007.
Gallagher KM et al. Predictors of influenza vaccination on HIV-infected patients in the United States, 1990-2002. Journal of Infectious Diseases 196, 339-342, 2007.