H1N1 Re-infections Raise Pandemic Concerns

Recombinomics Commentary 02:30
November 25, 2009

Dr. Debra Parsons, a pediatrician at Kid Care West in Cross Lanes, was met with reactions of doubt from local health officials last month when she said two flu tests had come back positive for H1N1, or swine flu.
Parsons first came down with the virus, complete with all the telltale symptoms, in August.
Her son became ill at the same time with the same symptoms. Figuring they had the same bug, Parsons tested herself to see what it was.
The test came back positive for Influenza A, so the lab at Charleston Area Medical Center sent it to be sub-typed. Parsons was positive for H1N1.
Parsons and her son recovered, but in October they started having the same symptoms, but they became much worse.
They were both tested this time, and the results were the same -- they were positive for Influenza A and then H1N1.
"It was swine flu both times," Parsons said.
The above comments on lab confirmed re-infection of two family memberstwo months apart by swine H1N1.  These confirmations are supported by many anecdotal reports of similar re-infections.  The timing of these infections allowed for easy identification, because at the time there was no seasonal flu, so identification of infections was straight-forward.  Moreover, such infections in school aged children and parents are common because H1N1 infections exploded when school began.
At the time however, the H1N1 virus was evolving slowly, reflecting an ease of infection of a naïve population.  The jump from swine H1N1 into humans allows for infections with low doses of virus.  Low concentration of virus produces a mild infection and a weak antibody response.  The rapid spread creates widespread antibody, but the low level allows for re-infection from individuals with a higher viral load.  A higher viral load can be created in a school environment, where some students could be infected multiple times because of frequent contact with infected students.
Thus, the increased viral load could overcome the weak immune-response and re-infect those infected earlier, leading to a second wave.  However, the higher viral load leads to more serious infections, especially for these not infected in the first wave.  Consequently more previously health young adults develop more serious symptoms, leading to an increase in hospitalizations and deaths.  The higher viral load, especially when combined with receptor binding domain changes such as D225G can lead to the type of cases seen in Ukraine, where a high percentage of young adults develop infections that destroy both lungs in a matter of  a few days.
In many areas, including Ukraine, this wave is subsiding, but the holiday season will lead to new infections by viruses with regional markers, leading to a third wave in early 2010