Influenza: A check list

Although a few areas remain unaffected by influenza, the disease has been reported from almost 40 states and data presented at the Advisory Committee on Immunization Practices meeting last month show the disease is now widespread.

The number of cases of influenza is greater than usual for this time of year. This might suggest a very bad year, or that influenza will peak earlier than usual.

The novel influenza strain does not appear to be as virulent as the pandemic strains of the past, but it is infecting a relatively naïve population immunologically. Only us older critters seem to have encountered an antigenically similar strain recently enough to render us less susceptible to this novel strain than to seasonal influenza. Thus this time we are not in the high-risk priority vaccine group. Relative sparing of the older age group had been observed in the 1977 reappearance of H1 after a 20-year absence.

Recognizing that some offices might be overwhelmed as the epidemic grows, and fear increases exponentially, CDC has issued some guidelines for triaging adults but not for children.

Differentiating respiratory disease caused by influenza virus from that caused by other respiratory viruses in children is difficult in many cases. Conversely, influenza virus might not produce that classic adult picture of fever, coryza, cough, muscle aches, chills, sore throat, lethargy and anorexia in younger children. It may present instead as croup, pneumonia, bronchiolitis or simply as an upper respiratory infection.

Having a “one set of symptoms defines all” message on your answering machine to provide guidance may not work in a practice where some parents are overanxious and others are oblivious.

Advise parents who elect to wait it out they should bring children in if their child’s illness continues to worsen, if they experience dyspnea or cyanosis or if their fever increases or if they appear lethargic or will not take fluids.

Superinfecting bacteria, such as staphylococcus and pneumococcus, has caused a good number of the pediatric deaths. When these children come in for their influenza vaccines, it is a good idea to check their pneumococcal and the Haemophilus influenzae type b vaccine status.

The vaccine

According to ACIP data, both live, attenuated and inactivated influenza A (H1N1) 2009 monovalent vaccine formulations are available from several manufacturers, but vaccine supply has fallen short of projections. As of early this month, only 43 million doses of the H1N1 vaccine were projected to actually be delivered.

If the live vaccines are used, both types — seasonal and novel — should not be given simultaneously but administration should be separated by a month.

The two killed vaccines may be given at the same time in separate syringes. Children younger than 9 years who have not received two doses of each vaccine in the same season should receive two doses one month (or 21 days) apart.

Until sufficient quantities of vaccine are available, it should be given preferably to pregnant women, people who live with or care for children younger than 6 months of age, health care and emergency medical services personnel with direct patient contact, children 6 months through 4 years (through 24 years when supplies are adequate), and those 5 through 24 years of age who have chronic medical conditions (expanded to 25 through 64 when supplies are adequate). Particular efforts should be made to protect those who have neurological impairment that might compromise respiration or clearing secretions.

There has been a surprisingly significant number of parents who are not taking their children to receive the new influenza vaccine. The reasons generally given are concern about safety or effectiveness. I do not know if anyone asked specifically about objections to the number of shots required.

One of the issues is the concern about mercury in the vaccines. There are single dose vaccines available that do not contain thimerosal or only trace amounts (Table 1). The trace amounts are less than one microgram, which is left over from the manufacturing process and that is far less than that contained in a portion of tuna fish.

The other concern is that of Guillian-Barre syndrome. GBS occurs in 3,000 to 5,000 Americans each year and often is associated with Campylobacter infections.

As millions of us receive influenza vaccine each year, some are bound to get both vaccines and Guillian-Barre syndrome. There does not appear to be an increased risk of GBS attributable to getting influenza vaccine. In 1976, there appeared to be a slightly increased risk but this has not been associated with any subsequent vaccine despite carefully monitoring efforts.

Diagnosis of influenza

As indicated, the clinical picture is not unique in young children. What is more, the novel influenza A H1N1 cannot be distinguished from seasonal influenza except that the former appears to be associated with more gastrointestinal symptoms.

The sensitivity of the rapid tests are “iffy” for seasonal influenza and even less sensitive for the novel flu (see related story). PCR is the “gold standard” but is not likely to be generally available.

Antiviral drugs

The amantadines are not useful for novel influenza A, although they remain the drugs of choice for seasonal influenza A strains. The neuraminidase inhibitors are recommended for infants younger than 2 years, pregnant women (although it is a class C drug), patients hospitalized with novel influenza, those with deteriorating conditions and those at high risk. These medications should be started promptly after onset, and directions should be clear as to whether the dose is in ml or mg as these have been confused.

There has been a shortage of liquid oseltamivir, which led to a release of stockpiled drug and alternatively instructions for compounding the liquid form from capsules. The FDA has temporarily approved the use of this drug in infants younger than 1 year. (Table 2).

Preventing spread

There has been some controversy about the virtues of masks for health care workers (see related story).

It is recommended that patients with influenza stay at home for one week from the onset of respiratory symptoms and at least one day after effervescence. Last but not least, there has been an appeal to the general public to observe “proper hygiene.” This advice is something for all of us and our patients to observe.