Doctors across the U.S. are saying this flu season is shaping up to be one of the worst they've seen in years. The flu strain causing the most problems this year, is particularly hard on children and the elderly.

Health experts are not ready to say the flu is at "epidemic" levels just yet. But they are concerned because the flu vaccine is only estimated to be 30 percent effective against this year's main flu strain.

Local health workers said they are keeping a close eye on the case count. They said each flu season is different, so it's hard to compare one year to another, but they are preparing for the worst.

Flu season generally begins in October, but can peak at different times of the year.

"Last year we peaked towards the end of February, the previous years we peaked in march, previous to that we peaked around the first of January" Kent County Health Department Epidemiologist Brian Hartl said.

Within the last couple of weeks, the Kent County Health Department said there's been an increase in the number of cases reported.

"People who go into their emergency departments or to their private physician and get an Influenza test so we've seen an increase in those in the past two weeks as well as an increase in the number of patients that are visiting local emergency departments for flu like illness," Hartl said.

Eighty percent of the strains tested at the state level show the Type A virus H3N2.

"We know that H3N2 subtypes generally don't receive as much protection form the influenza vaccine," Hartl said.

Between December 31 and January 6, there were 263 cases reported. To date, 655 cases of influenza have been reported. w

"We are either nearing or at the peak of activity, we won't know that until next week when we get more data and see how the trends are moving," Hartl said.

Hartl said it's challenging to compare last year's data to this years, because it's a different strain of influenza and the peak months are different.

"We would be much higher this year than we were at this point last year, simply because Influenza peaked at the latter point of February," Hartl said.

Mercy Health Muskegon confirms 129 cases of Influenza A which is the H3N2 strain, from December 2 to January 6. Mercy Health St. Mary's confirms 196 of the same strain, during the same time period.