By Laila Kearney
April 23 (Reuters) - A Southern California city has seen a spike in reported whooping cough cases so far this year, with the number of infections nearly tripling compared to all of last year, possibly due to a less potent vaccine or lower vaccination rates, officials said on Wednesday.
Some 43 cases of whooping cough, or pertussis, have been documented since January in Long Beach, a city of about 470,000, up from 15 cases reported in all of 2013 and four cases reported in 2012, Long Beach Health Officer Michael Kushner said.
"We've never had so many cases in such a short amount of time," Kushner said.
Whooping cough is a highly contagious bacterial infection that often begins with cold-like symptoms and a mild cough, followed by severe coughing that can last for several weeks.
The infection, which can be treated with antibiotics, is spread through the coughing or sneezing of an infected person. It is especially dangerous for young babies, who can develop pneumonia and other sometimes fatal complications.
Kushner said the rise in whooping cough cases in Long Beach was likely due to a drop in vaccinations or booster shots, a weakened vaccine or infections that are left untreated.
Across the nation, the number of reported whooping cough cases has ballooned since the 1990s, when there were fewer than 10,000 reported infections each year, according to the U.S. Centers for Disease Control and Prevention.
Overall, U.S. infections hit a 50-year high in 2012 with 48,277 reported cases, but the number dropped by half last year and appears to be decreasing slightly in 2014, said Centers for Disease Control and Prevention spokesman Jason McDonald.
McDonald said the long-term increase could be linked to the vaccine, which was modified in the 1990s to decrease adverse side effects, such as seizures.
"What we may have done is given up to a little bit of potency in doing that," McDonald said. Vaccination rates have consistently remained high and are likely not the cause of any spikes in reported cases, he added.
The Centers for Disease Control are currently researching possible potency problems with the current vaccine, McDonald said. (Editing by Cynthia Johnston and Diane Craft)